GSSA-Publications-2006

Abstract:

Abstract: To test if native perennial bunchgrasses cultivate the same microbial community composition across a gradient in land-use intensification, soils were sampled in fall, winter and spring in areas under bunchgrasses ([`]plant') and in bare soils ([`]removal') in which plots were cleared of living plants adjacent to native perennial bunchgrasses (Nassella pulchra). The gradient in land-use intensification was represented by a relict perennial grassland, a restored perennial grassland, and a perennial grass agriculture site on the same soil type. An exotic annual grassland site was also included because perennial bunchgrasses often exist within a matrix of annual grasses in California. Differences in soil resource pools between [`]plant' and [`]removal' soils were observed mainly in the relict perennial grassland and perennial grass agriculture site. Seasonal responses occurred in all sites. Microbial biomass carbon (C) and dissolved organic C were greater under perennial bunchgrasses in the relict perennial grassland and perennial grass agriculture site when comparing treatment means of [`]plant' vs. [`]removal' soil. In general, soil moisture, microbial respiration, and nitrate decreased from fall to spring in [`]plant' and [`]removal' soils, while soil ammonium and net mineralizable nitrogen (N) increased only in [`]plant' soils. A canonical correspondence analysis (CCA) of phospholipid fatty acid (PLFA) profiles from all sites showed that land-use history limits the similarity of microbial community composition as do soil C and N dynamics among sites. When PLFA profiles from individual sites were analyzed by CCA, different microbial PLFA markers were associated with N. pulchra in each site, indicating that the same plant species does not retain a unique microbial fingerprint across the gradient of land-use intensification.

Abstract: Spotted knapweed is an important weed of rangeland in the northwestern United States and western Canada, and has been the focus of considerable biological control efforts. Cyphocleonus achates, a Eurasian root weevil, has been released as a biocontrol agent against the weed in many areas of Montana and the Pacific Northwest. Spotted knapweed plant density was monitored over a 11-year period (1993-2004) at two sites in western Montana where C. achates was released. Spotted knapweed density declined significantly over time at both sites (99 and 77%, respectively), after C. achates numbers increased dramatically at both sites. The average annual population growth rate of C. achates during 1993-1995 was 14% at the two sites, compared to 10% during 1995-1998. The weevil population radially expanded a distance of 73 m per year at one study site compared to 99 m per year at the other site. The estimated C. achates population increase at the two sites was similar: in 1998, the C. achates population estimate for one site was 90,776 in a 23 ha area of occupation, compared to 97,173 in a 29 ha area at the other site. Evidence suggests that C. achates played a major role in the spotted knapweed population decline. Following the decline of spotted knapweed, two annual exotic weeds, Bromus tectorum and Descurainia sophia, became major components of the new plant community, with B. tectorum becoming the dominant plant. By 2004, B. tectorum comprised 89 and 50% of the replacement vegetation at the two sites.

Abstract: Approximately 70,150 dry Mg of biosolids from over 450 wastewater treatment facilities are applied to the semi-arid rangelands of Colorado every year. Research on semi-arid grassland responses to biosolids has become vital to better understand ecosystem dynamics and develop effective biosolids management strategies. The objectives of this study were to determine the long-term (~12 years) effects of a single biosolids application, and the short-term (~2 years) effects of a repeated application, on plant and microbial community structure in a semi-arid grassland soil. Specific attention was paid to arbuscular mycorrhizal fungi (AMF) and linkages between shifts in plant and soil microbial community structures. Biosolids were surface applied to experimental plots once in 1991 (long-term plots) and again to short-term plots in 2002 at rates of 0, 2.5, 5, 10, 21, or 30 Mg ha-1. Vegetation (species richness and above-ground biomass), soil chemistry (pH, EC, total C, total N, and extractable P, NO3-N, and NH4-N), and soil microbial community structure [ester-linked fatty acid methyl esters (EL-FAMEs)], were characterized to assess impacts of biosolids on the ecosystem. Soil chemistry was significantly affected and shifts in both soil microbial and plant community structure were observed with treatment. In both years, the EL-FAME biomarker for AMF decreased with increasing application rate of biosolids; principal components analysis of EL-FAME data yielded shifts in the structure of the microbial communities with treatment primarily related to the relative abundance of the AMF specific biomarker. Significant (p<=0.05) correlations existed among biomarkers for Gram-negative and Gram-positive bacteria, AMF and specific soil chemical parameters and individual plant species' biomass. The AMF biomarker was positively correlated with biomass of the dominant native grass species blue grama (Bouteloua gracilis [Willd. ex Kunth] Lagasca ex Griffiths) and was negatively correlated with western wheatgrass (Agropyron smithii Rydb.) biomass. This study demonstrated that applications of biosolids at relatively low rates can have significant long-term effects on soil chemistry, soil microbial community structure, and plant community species richness and structure in the semi-arid grasslands of northern Colorado. Reduced AMF and parallel shifts in the soil microbial community structure and the plant community structure require further investigation to determine precisely the sequence of influence and resulting ecosystem dynamics.

Abstract: In semiarid savannas of Southern Africa current land use practices and climate change may lead to substantial changes of vegetation structure in the near future, however uncertainty remains about the potential consequences and the magnitude of change. In this paper we study the impact of climate change, cattle grazing, and wood cutting on shrub cover dynamics in savannas of the southern Kalahari. We use an established savanna ecosystem model to simulate landscape dynamics in terms of rainfall, fire and distribution of the dominant tree Acacia erioloba. We then incorporate these data into a spatial population model of the common, fleshy-fruited shrub Grewia flava and investigate shrub cover dynamics for a period of 100 years. Depending on the intensity of commercial wood cutting practices tree removal of A. erioloba led to a strong decline of the G. flava population, as shrub recruitment is concentrated in tree sub-canopies due to bird-mediated seed dispersal. Under climate change shrub cover slightly decreased with decreasing precipitation and was unchanged with increase in precipitation variability. Contrarily, grazing by cattle strongly increased shrub cover and facilitated shrub encroachment because of cattle-induced distribution of G. flava seeds into the matrix vegetation. Knowledge of the latter process is particularly important because shrub invasion is a major concern for conservation and savanna rangeland management as a result of its adverse effects on livestock carrying capacity and biodiversity.

Abstract: Several stable carbon isotopic studies have shown that South African australopiths consumed significant quantities of C4 resources (tropical grasses, sedges, or animals that eat those foods), but relatively little is known about the consumption of such resources by chimpanzees. Here, we present stable carbon isotopic data for 36 chimpanzee hair samples from Fongoli, one of the driest and most open areas inhabited by chimpanzees. These data suggest that the Fongoli chimpanzees consume little in the way of C4 vegetation or animals that eat such vegetation, even though these resources are locally abundant and preferred fruits are more widely scattered than at most chimpanzee study sites. The homogeneity of the Fongoli results is especially striking and recalls the narrow isotopic distribution of stenotopic savanna mammals. This is in stark contrast to what has been observed for australopiths, which had highly variable diets and consumed about 35% C4 vegetation on average. Carbon isotope data for modern and fossil Papio depict a dietarily variable genus with a tendency to consume C4 vegetation. This trophic flexibility, or willingness to consume C4 savanna resources, may make Papio a more profitable ecological analog for australopiths than chimpanzees.

Abstract: A new biozonation is proposed for the Late Carboniferous strata of the northeastern Paraná Basin (São Paulo and Paraná States), based on well-preserved palynological assemblages recovered from outcrops and core samples retrieved from the Itararé Subgroup. Assemblages include forty-nine species of trilete spores and twenty-five pollen species. The oldest biozone, the Ahrensisporites cristatus Interval Zone (AcZ), in the basal portion of the Itararé Subgroup, includes eleven exclusive spore species, and is assigned a Pennsylvanian (late Bashkirian to Kasimovian) age. The overlying proposed biozone, the Crucisaccites monoletus Interval Zone (CmZ), dated late Pennsylvanian (Kasimovian to Gzhelian), ranges approximately from the top of the lower portion to the middle portion of the Itararé Subgroup, bears only one exclusive species of pollen. Both zones are characterized by the dominance of trilete spores and monosaccate pollen grains, including also few taeniate pollen grains. Furthermore, the basal Protohaploxypinus goraiensis Subzone of the Vittatina costabilis Interval Zone (VcZ) is broadly recognized for the first time in the upper portion of the Itararé Subgroup in the northeastern Paraná Basin. This subzone is attributed to the Early Permian (Early Cisuralian), and is characterized by the dominance of monosaccate pollen grains, a significant increase of taeniate grains (mainly Protohaploxypinus spp.), apart from the appearance of polyplicate pollen (Vittatina spp.). Reference sections and the main characteristics of the two new zones (AcZ and CmZ) are presented, along with a preliminary palynological correlation and discussion on their ages.

Abstract: Systematic conservation planning is widely considered the most effective approach for designing protected area and other ecological networks. However, many conservation practitioners still ignore these methods and we suggest that five perceived limitations of this process are affecting its uptake. These perceptions are that (1) systematic conservation planning software is difficult to use, (2) the process requires extensive biodiversity distribution data, (3) setting targets for representing conservation features is not possible, (4) the advantages of systematic conservation planning do not outweigh the costs, and (5) the resulting plans often identify unsuitable areas. Here we review these perceived limitations and argue they are all misplaced, although we recognize difficulties in the target setting process. We then illustrate the value of systematic conservation planning to practitioners using a case study that describes a low-cost exercise from Maputaland, South Africa. This preliminary conservation assessment measured the effectiveness of the existing reserve system and identified a number of candidate areas that could be the focus of community- or privately-run ecotourism or game ranching ventures. Our results also emphasize both the importance of producing planning outputs that are specifically targeted for stakeholders, and the role of systematic conservation planning in providing a framework for integrating different provincial, national and transnational conservation initiatives.

Abstract: Epidermal conductance (gmin) is water lost through the cuticle and stomata of plants when stomatal conductance is minimal. Low gmin may affect survival of perennial grasses by maintaining tissue hydration during drought. If true, populations from environments where drought is severe may exhibit reduced gmin compared to those from less arid environments. Success of invasive grasses may also be associated with reduced gmin compared to non-invasive competitors. Using plants grown in a single environment, we measured gmin of leaves from populations of Digitaria californica from environments with similar annual precipitation but differing in average drought severity (southern Arizona and western Texas, USA), and a population of the exotic species Eragrostis lehmanniana that has invaded sites occupied by D. californica in Arizona. Epidermal conductance was lower in the D. californica population from the more arid environment (Texas). Likewise, gmin was lower in E. lehmanniana than in the Arizona D. californica population. Shoot biomass production as a fraction of gmin was higher in E. lehmanniana than in the D. californica populations and was higher in the Texas D. californica population than in the Arizona population. This suggests that low gmin may be a component of drought avoidance in these grasses.

Abstract: Opuntia is a drought tolerant crop and even the smallest amount of water is absorbed efficiently through the shallow and horizontally spread root system. However, there is a lack of knowledge on the root dynamics of cactus pear for sustainable production of fodder and fruit in the drier areas. This study, conducted during the 2003/2004 growing season on two-year-old Opuntia ficus-indica (L.) Miller (cultivar Morado-green cladode) and O. robusta Wendel. (cultivar Monterey-blue cladode) plants in the field was therefore aimed at quantifying root distribution with distance and depth from the stem. Root growth was expressed in terms of both mass and length, and water-use efficiency (WUE) was defined as the cladode dry mass production per unit of evapotranspiration. In both species most roots were concentrated in the first 150 mm soil layer. After only two growing seasons the roots spread as far as 2.5 m from the stem for both species. The total root dry weight production calculated per plant up to a depth of 1200 mm, was 239 and 316 g per plant or kg ha- 1 for O. ficus-indica and O. robusta respectively. The thickest roots developed directly from the planted cladode and were 9.1 mm thick for O. ficus-indica and 6.3 mm for O. robusta. Opuntia robusta showed a finer root system than that of O. ficus-indica. After two growing seasons 3407 and 2702 kg ha- 1 aboveground dry mass was produced by O. ficus-indica and O. robusta respectively. The WUE of O. ficus-indica (6.52 kg ha- 1 mm- 1) was significantly higher than that of O. robusta (5.39 kg ha- 1 mm- 1). The roots comprised only 11% of the total biomass for O. robusta and 7% for O. ficus-indica. Such root adaptations of this species are in addition to the classical physiological and structural modifications of CAM plants to tolerate prolonged drought.

Abstract: The size and species composition of the soil seed bank of southern Ethiopia rangelands were examined under three land use systems (communal land, a government ranch and traditional grazing reserves) and along a distance gradient (near, middle and far) from water sources. Soil seed bank sampling was carried out at the end of the growing season from 0.25 m- 2 quadrates 30 mm deep. The aboveground species composition was also compared. Of the total plant species identified in the soil seed bank in the greenhouse, 25% were grasses and 75% non-grasses. The near, middle and far sites from water was dominated by Leucas glabrata, Verbesina encelioides and Lintona nutans, respectively. Lepthotrium senegalensis made up 67% of the total composition of the soil seed bank in the traditional grazing reserve. Graminoid seedling density at the traditional grazing reserve (798.8 seedlings m- 2) was higher (P < 0.01) than that of the ranch and communal sites, but did not vary significantly along the distance gradient from water (average 239.2 seedlings m- 2). Non-graminoid seedling density did not vary much (P > 0.05) between the land use systems (average 128.9 seedlings m- 2) and along the distance gradients from water (average 183.7 seedlings m- 2). Sorensen's similarity index of the aboveground vegetation and the associated seed bank was low at all the sites. Difference in grazing pressure between the land use systems was one of the most likely causes of variations in the soil seed bank density and botanical composition of graminoids. The non-significant differences in the graminoid seed bank density along the distance gradients from water were due to similar population of grasses and may not explain the levels of grazing impact and disturbance. Regeneration from the soil seed bank may have a profound effect in restoring the composition of the grass layer in the degraded Borana rangelands if sustainable management practices are applied and sufficient rest periods followed. By translocating seed rich topsoil from the grazing reserves to degraded grazing areas, the soil seed bank can be used to develop valuable grass species at small community level.

Abstract: This paper provides an analysis of the physical and chemical characteristics of cyanobacterial soil crusts in the Molopo Basin, South Africa. It details the influence that soil type, livestock disturbance and shrubs have on the spatial distribution of crusts. Four morphologically distinct cyanobacterial crusts were identified and crust cover ranged from 24% to 55%. Crust cover was significantly higher and characterized by darkened type 3 and 4 crusts on Ironstone soils compared to Kalahari Sand. More frequently disturbed sites had the least crust cover and had predominantly type 1 and 2 crusts. Type 3 and 4 crusts are more common on the less disturbed sites and under the canopies of Acacia mellifera where soils are protected from livestock disturbance. Total nitrogen concentrations were significantly higher in crusts compared to unconsolidated soil. There is also a strong correlation between the pH and NH4+-N concentrations in crusts and the soil immediately below the crust, suggesting that crusts have an influence on some of the properties of the underlying soil. If the A. mellifera can utilize additional nitrogen from crusts it may provide a competitive advantage to their establishment in formerly grass-dominated grazing lands.

Abstract: Pastoral communities in East Africa are facing considerable challenges arising from shifts in land tenure policy from communal to individual landholdings and high human population growth rates. Over the last 30 years, livestock-to-human ratios have generally declined to levels that will no longer support pure pastoralism. Many Maasai have thus diversified into cultivation, wage labour, and small businesses. Livelihood expectations are rising, with concomitant increases in the need for cash. We describe the modification of PHEWS, a simple rule-based model that tracks cash flow and calories in agro-pastoral households. We use it, coupled to Savanna, a sophisticated ecosystem model, to quantify some of the effects of subdivision and land fragmentation on household livestock numbers and on food security. For the group ranches simulated, model outputs indicate that subdivision results in substantial reductions in livestock numbers, partially because households have to sell more animals to generate the cash needed, with serious long-term consequences on herd sizes and food security. If subdivision occurs, even to parcels as large as 196 km2, livelihood strategies may need to be modified to maintain current levels of household well-being. Model results have been discussed in community meetings in southern Kajiado, but more work is needed on communication mechanisms to utilise more effectively the results of imperfect but useful integrated assessments of complex problems concerning land use and human well-being.

Abstract: Riparian meadows of southern Patagonia are temporally and spatially heterogeneous habitats. They are thought to play a key role in regulating the dynamics of arid grazed steppes of the region. We conducted a 2-year study with sheep to determine the influence of two grazing conditions (deferment and spring grazing) on structural and nutritional parameters of three vegetation types apparently associated with a soil moisture gradient in a riparian meadow in southern Santa Cruz (Argentina). Spring deferment allowed forage accumulation in very moist and intermediate vegetation types by the beginning of the summer and had no detrimental impact on forage quality. Deferment had no effect on biomass accumulation of the drier vegetation type at our study site. Structural attributes of the vegetation appeared to affect spatial grazing patterns of sheep. Soil-related patchiness, rather than sheep grazing, appeared to control vegetation structure and nutritional value. The proportion of more mesic plant communities in riparian habitats of Patagonia could determine the outcome of plant-animal interactions in these systems. Practical recommendations of grazing capacity in paddocks, or more theoretical considerations of ecosystem dynamics of the Patagonian steppes need to explicitly consider the internal patchiness of riparian habitats.

Abstract: Degradation in arid and semi-arid regions can be ascribed primarily to environmental conditions such as extreme changes in temperature and erratic rainfall patterns. Seed germination and seedling growth of three grass species (Anthephora pubescens, Heteropogon contortus and Themeda triandra) indigenous to arid and semi-arid regions of southern Africa were assessed under controlled conditions that simulated drought stress using polyethylene glycol (PEG) 6000. Exposure to water potentials below - 0.3 MPa significantly decreased germination rates and shoot lengths for all three species, despite slight differences in their sensitivities to osmotic stress. More dramatic differences between the species were evident when the effects of water stress on root growth were evaluated. These findings form the basis for future trials involving the use of indigenous grasses in the restoration of rangelands.

Abstract: This paper evaluated the capacity of SPOT VEGETATION time-series to monitor the vegetation biomass and water content in order to improve fire risk assessment in the savanna ecosystem of Kruger National Park in South Africa. First, the single date and integrated vegetation index approach, which quantify the amount of herbaceous biomass at the end of the rain season, were evaluated using in situ biomass data. It was shown that the integral of the Ratio Vegetation Index (iRVI) during the rain season was the most suitable index to estimate herbaceous biomass (R2 = 0.69). Next, the performance of single, greenness, and accumulated remotely sensed fire risk indices, related to vegetation water content, were evaluated using fire activity data. The Accumulated Relative Normalised Difference Vegetation Index Decrement (ARND) performed the best when estimating fire risk (c-index = 0.76). Finally, results confirmed that the assessment of fire risk was improved by combination of both the vegetation biomass (iRVI) and vegetation water content (ARND) related indices (c-index = 0.80). The monitoring of vegetation biomass and water content with SPOT VEGETATION time-series provided a more suitable tool for fire management and suppression compared to satellite-based fire risk assessment methods, only related to vegetation water content.

Abstract: New detailed biome reconstructions are proposed in East Africa from modern pollen data derived from 150 sites located in northern Kenya (40 sites), north-western Uganda (51 sites) and southern Tanzania (59 new sites presented as pollen diagram), which are representative of the major vegetation associations occurring in seven phytogeographical regions, mosaics or centres of endemism. We use the standard biomisation method previously published for the African continent, but we reconsider the taxa assignment to plant functional types. We include in this approach all identified taxa (408) except aquatics, ferns and exotic taxa. The method is validated by comparison with local vegetation data and we show that 124 (82.6%) sites are assigned to the correct biome and that for all the biomes under investigation, the number of correct assignments always exceeds the number of incorrect ones. When an incorrect biome reconstruction occurs, mainly toward drier biomes, this is generally linked to the local open/degraded structure of the original vegetation or to the occurrence of a mosaic of open/closed vegetation. In turn, most of the reconstructions of more humid/closed biomes than the corresponding local vegetation (8.6%) remain unexplained. A comparison of our reconstructed biomes with the main East African vegetation types of White's map indicates that 121 (80.6%) sites are assigned to the correct biomes. However, the majority of sites are incorrectly reconstructed compared to Olson and IGBP maps from satellite data, mainly due to incorrect allocation of the land cover classes compared to the potential vegetation. The application of this method to our pollen data set demonstrates that modern pollen assemblages can successfully reconstruct the main modern East African vegetation types.

Abstract: Conventional wisdom ties the origin and early evolution of the genus Homo to environmental changes that occurred near the end of the Pliocene. The basic idea is that changing habitats led to new diets emphasizing savanna resources, such as herd mammals or underground storage organs. Fossil teeth provide the most direct evidence available for evaluating this theory. In this paper, we present a comprehensive study of dental microwear in Plio-Pleistocene Homo from Africa. We examined all available cheek teeth from Ethiopia, Kenya, Tanzania, Malawi, and South Africa and found 18 that preserved antemortem microwear. Microwear features were measured and compared for these specimens and a baseline series of five extant primate species (Cebus apella, Gorilla gorilla, Lophocebus albigena, Pan troglodytes, and Papio ursinus) and two protohistoric human foraging groups (Aleut and Arikara) with documented differences in diet and subsistence strategies. Results confirmed that dental microwear reflects diet, such that hard-object specialists tend to have more large microwear pits, whereas tough food eaters usually have more striations and smaller microwear features. Early Homo specimens clustered with baseline groups that do not prefer fracture resistant foods. Still, Homo erectus and individuals from Swartkrans Member 1 had more small pits than Homo habilis and specimens from Sterkfontein Member 5C. These results suggest that none of the early Homo groups specialized on very hard or tough foods, but that H. erectus and Swartkrans Member 1 individuals ate, at least occasionally, more brittle or tough items than other fossil hominins studied.

Abstract: Ants are increasingly being recognized as useful tools for land managers to monitor ecosystem conditions. However, despite an abundance of studies on ant responses to both environmental disturbance and land management techniques, an analysis of the practice and value of including ants in monitoring is lacking. Consequently, conservation managers are left with little guidance as to if, when, and how ants can be used to assess conservation activities. Based on our review of approximately 60 published studies, we outline five areas where ants provide valuable information for management-based monitoring: (1) to detect the presence of invasive species, (2) to detect trends among threatened or endangered species, (3) to detect trends among keystone species, (4) to evaluate land management actions, and (5) to assess long-term ecosystem changes. We also discuss practical considerations when designing a monitoring framework for ants, including appropriate methods, taxonomic resolution for sampling, and spatial and temporal scale. We find that when integrated with management goals, monitoring ants can provide information over the short-term on topics such as the status of invasive or keystone species, as well as over longer time frames, for instance the impact of climate change. Overall, we conclude that ants merit monitoring based on their inherent ecological qualities, independent of any "indicator" attributes they might have.

Abstract: There are many individuals in the Bredasdorp/Elim area who still use plants as medicines to treat many conditions. This study aimed to document some of this knowledge and present an inventory of all the plants in use in the area. Over 40 individuals were interviewed from old age homes, community centres for the elderly as well as people who were known for their knowledge in this matter. The information was gathered by means of questionnaires. In total, 36 plant species from 19 families were found to be in general use in the area. Only 58% of these plants are indigenous to South Africa, 33% are introduced species and 9% are naturalized species. The dominant families were Asteraceae, Lamiaceae, Alliaceae and the Solanaceae. Many of the plants in use are commonly used in traditional medicine around South Africa and share many of the same uses. Some uses, which have not been seen in the consulted literature, have also been documented. A more structured questionnaire was used to determine which plants were most popular for particular ailments. It was found that Artemisia afra and Ruta graveolens were the most popular.

Abstract: Using new tools (boosted regression trees) in predictive biogeography, with extensive spatial 23 distribution data for >19�000 species, we developed predictive models for South African plant species richness patterns. Further, biome level analysis explored possible functional determinants of country-wide regional species richness. Finally, to test model reliability independently, we predicted potential alien invasive plant species richness with an independent dataset. Amongst the different hypotheses generally invoked to explain species 30 diversity (energy, favorableness, topographic heterogeneity, irregularity and seasonality), results revealed topographic heterogeneity as the most powerful single explanatory variable for indigenous South African plant species richness. Some biome-specific responses were observed, i.e. two of the five analyzed biomes (Fynbos and Grassland) had richness best explained by the �species-favorableness� hypothesis, but even in this case, topographic heterogeneity was also a primary predictor. This analysis, the largest conducted on an almost exhaustive species sample in a species-rich region, demonstrates the preeminence of topographic heterogeneity in shaping the spatial pattern of regional plant species richness. Model reliability was confirmed by the considerable predictive power for alien invasive species richness. It thus appears that topographic heterogeneity controls species richness in two main ways: firstly, by providing an abundance of ecological niches in contemporary space (revealed by alien invasive species richness relationships) and secondly, by facilitating the persistence of ecological niches through time. The extraordinary richness of the South African Fynbos biome, a world-renowned hotspot of biodiversity with the steepest environmental gradients in South Africa, may thus have arisen through both mechanisms. Comparisons with similar regions of the world outside South Africa are needed to confirm the generality of topographic heterogeneity and favorableness as predictors of plant richness.

Abstract: 1. Gradients of animal impact known as piospheres tend to develop around artificial watering points, particularly in arid zones. Such grazing gradients represent a potential opportunity for differentiating the long-term effects of livestock activity from other environmental patterns. In this study, the impact of watering point provision on the plant cover, species richness and community structure of Karoo shrublands, South Africa, was investigated in the context of the evolutionary history and current grazing management practices of the region. 2. The impacts of watering point provision were investigated by sampling plant cover and composition along transects placed at set distances, ranging from 10 m to 2200 m, from 11 watering points. 3. Karoo vegetation cover and structure are relatively resilient to livestock grazing. Karoo plant diversity, as measured by species richness, evenness and dominance, was not as resilient. Twice as many species decreased as increased near watering points. The majority of species that decreased were regarded as being highly palatable to livestock. Heavy grazing, leading to death or repeated reproductive failure, is the most likely mechanism leading to the decline of such species. 4. The highly disturbed area immediately adjacent to watering points was dominated by forbs and contained a large proportion of alien species. Adjacent to this was a zone dominated by widespread shrub species of medium to low palatability. Areas most distant from watering points contained a greater proportion of species known to be highly palatable to livestock. The ability of dominant Karoo shrubs to tolerate heavy grazing may have allowed rangeland managers to maintain stocking rates above that which can be tolerated by the majority of species but which are supported by a minority of grazing-tolerant species. 5. Synthesis and applications. Highly palatable species are more abundant in areas distant from water points. Larger paddocks therefore provide a refuge for sensitive species that might otherwise be lost from the rangeland as a whole. Species that tend to occur away from watering points represent potentially useful indicators of grazing pressure. The use of these species as indicators of rangeland condition among landowners should be promoted.

Abstract: Over 70% of South Africa is too arid for crop farming and is used for either commercial livestock ranching, communal livestock ranching, or game ranching. The inherently different management characteristics of these ranching systems and their effects on vegetation dynamics makes rangeland degradation a contentious issue. We used 500-m-long grazing gradients around water-points to evaluate the effects of management type on soil quality. Results showed significant negative effects of management type on soil parameters (i.e. soil pH, nitrogen, and organic carbon) within 0-100 m from the water-point. Commercial livestock ranching had the greatest negative effect on the immediate area around the water-point. Beyond 100 m, no effect of herbivore activity on soil parameters was detected under any management system.

Abstract: The global farming systems (GFS) approach is extended by adding a soil fertility and nutrient management dimension for Africa's forest-based, maize mixed, cereal-root crop mixed, and agro-pastoral millet/sorghum farming systems. Use is made of sustainable livelihood concepts, translated into farmer capitals (natural, physical, financial, human, social), and the indicator-based DPSIR (driving force-pressure-state-impact-response) framework for environmental reporting. State and impact indicators show, for each GFS, levels of nutrient stocks and flows, respectively. In case of nutrient depletion, soils may (i) initially still be fertile enough to provide reasonable and stable yields, (ii) support declining yields, or (iii) support low yields at low fertility level. In the latter case, food security is generally at stake. Response indicators include the level of uptake of improved integrated nutrient management strategies at land user level, and the enforcement of new and enabling pro-agriculture and pro-environment policies. Although the extended GFS have no direct relevance for farm-level interventions, the approach can be used to frame soil fertility research priorities and policies at a regional level.

Abstract: Sustainability indicators based on local data provide a practical method to monitor progress towards sustainable development. However, since there are many conflicting frameworks proposed to develop indicators, it is unclear how best to collect these data. The purpose of this paper is to analyse the literature on developing and applying sustainability indicators at local scales to develop a methodological framework that summarises best practice. First, two ideological paradigms are outlined: one that is expert-led and top-down, and one that is community-based and bottom-up. Second, the paper assesses the methodological steps proposed in each paradigm to identify, select and measure indicators. Finally, the paper concludes by proposing a learning process that integrates best practice for stakeholder-led local sustainability assessments. By integrating approaches from different paradigms, the proposed process offers a holistic approach for measuring progress towards sustainable development. It emphasizes the importance of participatory approaches setting the context for sustainability assessment at local scales, but stresses the role of expert-led methods in indicator evaluation and dissemination. Research findings from around the world are used to show how the proposed process can be used to develop quantitative and qualitative indicators that are both scientifically rigorous and objective while remaining easy to collect and interpret for communities.

Abstract: The objective of this study is to assess land-use intensity and the related biodiversity in agricultural landscapes of the EU25 for the current situation (2000), and explore future trends, based on the four EURURALIS scenarios up to 2030. Data from the Farm Accountancy Data Network (FADN) were used to classify farm types in 100 regions of the EU15, according to agricultural intensity. For the ten New Member States (EU10), which are not yet considered by the FADN, country level data were used to obtain similar farm types. Three processes were considered for the assessment of future trends in agricultural land-use intensity: (1) land-use change, (2) conversion into organic farming, and (3) changes in productivity of crop and grassland production. An ecosystem quality value was attributed to each farm type according to dose-effect relationships between pressure factors and biodiversity compared to the value for an undisturbed situation. The biodiversity in agricultural landscapes was then calculated as the average ecosystem quality multiplied by the relative area size of each farm type within a region. A similar method of attributing ecosystem quality values to other land-use types allowed comparison between different land-use types. Referring to the current situation, results indicate the lowest ecosystem quality values to be found in intensively used agricultural areas in lowlands (e.g. The Netherlands and northern France) and irrigation systems (e.g. Greece), whereas relatively high values are found in Spain and the New EU Member States. Scenario results show that for the A1 scenario (Global economy), the highest loss in ecosystem quality will take place in all regions in croplands and grasslands. The B2 scenario (Regional communities) provides the best opportunities to improve ecosystem quality of agricultural landscapes. In most scenarios, agricultural land is decreasing, while the remaining agricultural areas tend to be used more intensively. The negative impact of intensification on biodiversity is partly set off by (active or spontaneous) nature development on abandoned agricultural areas, but the overall trend seems to be generally negative. The strength of this methodology is that it provides a quick overview of land-use intensity change and biodiversity trends. Through the use of this farm-type level of analysis we have provided a good picture of the differences in land-use intensity and the related biodiversity between the EU regions and the scenarios.

Abstract: The Holocene climate evolution in Northern Africa is studied in a 9000-yr-long transient simulation with a coupled atmosphere-ocean-vegetation model forced by changes in insolation and atmospheric greenhouse gas concentrations. The model simulates in the monsoonal domains a significant decrease in precipitation under influence of the orbitally forced reduction in summer insolation. In the Western Sahara region, the simulated mid-Holocene transition from humid to arid conditions (the termination of the African Humid Period) is highly non-linear with the occurrence of centennial-scale climate fluctuations due to the biogeophysical feedback between precipitation and vegetation cover. This result is in agreement with proxy data from the Western Sahara region. The other monsoonal regions experience a more gradual climate evolution that linearly follows the insolation forcing, which appears in disagreement with available lake level records.

Abstract: Understanding the dynamics of semi-arid rangelands is a prerequisite for their proper management and long-term enclosure experiments are an important tool to investigate grazing impact. Hein [2006. The impacts of grazing and rainfall variability on the dynamics of a Sahelian rangeland. Journal of Arid Environments 64, 488-504] presents findings from a 10 year enclosure experiment in the semi-arid Ferlo, Senegal. His main conclusion is that current high-grazing pressure (0.15-0.20 TLU/h) negatively affects rain use efficiency and productivity especially in dry years because differences between treatments are significant for the whole period as well as for dry years only. A re-analysis under the framework of non-equilibrium theory of rangeland science leads to an alternative interpretation of the data. The vegetation on the more intensively grazed site possesses a remarkable resilience after the drought of 1983 and 1984. Standing crop recovers fast and for 2 years is even higher on the "high grazing" treatment than on the less intensively grazed treatment. Statistical analysis confirms this: a general linear model for standing crop against effective precipitation and grazing treatment finds a significant contribution of precipitation only (p<0.0001). Thus, vegetation dynamics in the semi-arid Ferlo largely follows a non-equilibrium dynamic as it is rather driven by precipitation dynamics than by grazing. This also leads to different policy implications: droughts reduce livestock density and thus are important to allow the vegetation to rest for 1 or 2 years.

Abstract: The objective of this paper is to examine the spatial variability of islands of enhanced hydrologic activity and its application to remediation of degraded arid and semi-arid ecosystems. Factors causing high spatial variability of water in arid regions include precipitation, soil, physiography, and vegetation. Inherent heterogeneity of arid lands causes areas of runoff and run-on which lead to development of islands of hydrologically enhanced biotic productivity. These hydrologic islands are observed at the individual plant scale as well as in large area patterns of banded vegetation, playettes and playas, and beaded drainage networks where run-on and infiltration stimulate vegetation growth. To remediate degraded rangeland, it may be prudent to mimic nature by diverting water to target areas to create patterns similar to natural islands of hydrologically enhanced biotic productivity. Installation of structures such as water ponding dikes can promote changes to natural vegetation patterns at a landscape scale.

Abstract: Grazing in arid Mediterranean ecosystems brings about changes in species diversity, but the best way to measure such changes is unclear. In this study we compared various methods in order to identify indicators that might be useful for the management and conservation of grazed arid Mediterranean ecosystems. Changes in community structure and composition were compared along a previously studied grazing gradient in Cabo de Gata-Nijar Natural Park. Plant diversity was measured by calculating diversity (Shannon information index), evenness (Pielou index) and richness (species number). Rarefaction curves were used to measure plant species richness and the results were compared with traditional richness values. Community structure was measured as the percentage of bare ground and the coverage of overall perennial grasses, Stipa tenacissima L., perennial shrubs and annual plants. Our results showed that the proportion of bare ground, the cover of perennial shrubs and the relative abundance of S. tenacissima are good indicators of grazing effects on vegetation. Overall plant community structure was more sensitive to the grazing gradient than were the diversity indices. Finally, the adequacy of standardized methods for comparing species richness (i.e. rarefaction curves) along a grazing gradient are discussed.

Abstract: The behaviour of sheep, goats and cattle on a shrub and tree savannah in the sub-humid zone of West Africa was studied during the dry (February to May), rainy (June to September) and cool season (October to January). Two mature females per animal species were followed by two observers during 3 days per month and behaviour activities were recorded every 15 min of the daily grazing time. When browsing, the plant name, plant part and plant height reached during prehension were recorded. The distance travelled and the grazing circuits were recorded with a step counter and a Geographic Position System device. The knowledge of farmers concerning appreciated browse species relative to the browse species consumed by animals in the area was also investigated. During the dry season sheep, goats and cattle spent around 25% of their time browsing and 20%, 16% and 31%, respectively, of their time grazing. During the cool season, goats (17%) browsed more than sheep (7%) and cattle (5%) (P < 0.05). During the rainy season, sheep browsed 20% of the time while cattle spent only 7% of their time browsing, while goats were tied, with no opportunity for browsing. Browsing leaves was the most important part of the browsing activity. During the cool season, browsing height was the same (1.0 m) for cattle and goats, but lower for sheep (0.6 m) (P < 0.05). In the dry and cool season, sheep and goats walked shorter distances than cattle. The plant species with the highest frequency of consumption were Acacia dudgeoni Craib, Ficus gnaphalocarpa (Miq.) A. Rich, Dioscorea togoensis Knuth, Cordia myxa L., and Manguifera indica L. for sheep and goats and Afzelia africana Sm., Kaya senegalensis (Desv.) A. Juss, Pterocarpus erinaceus Poir. and Dicrostachys cinerea (L.) Wight and Arn. for cattle. Species with a high frequency of citation by farmers were A. africana (92%), K. senegalensis (88%), P. erinaceus (86%), Faidherbia albida A. Chevalier (80%), A. dudgeoni (70%) and F. gnaphalocarpa (69%). In conclusion, browse species make an important contribution to the diet of ruminant animals in the sub-humid zone and farmers are familiar with the species consumed by ruminant animals.

Abstract: Native grass species are being considered in the restoration of degraded rangelands in Tunisia due to the failure of introduced species to adapt to the ecological constraints of the region. The objective of this study was to determine the effects of seed age and seedling depth on emergence and seedling vigor of Stipa lagascae, a perennial bunchgrass that is native to the region and shows promise as a species for restoration purposes. Total emergence percentage of seedlings and the coefficient of rate of emergence (CRE), the seedling vigour as well as above and below-ground biomass were measured. Younger seeds had higher emergence rates than older seeds. However, seed age did not affect variables associated with seedling vigour. Seeding depth significantly affected all parameters tested. A seeding depth of 4-6 cm was found to be optimal.

Abstract: We introduce the five rangeland types found in the arid and semiarid regions of South Africa, namely Arid Savanna, Arid Grassland, Nama-karoo, Succulent Karoo, and Thicket, and describe the important domestic herbivores associated with them. We continue by detailing the grazing management systems associated with the two major land tenure systems in the region, namely the freehold (commercial) and communal (subsistence). We briefly review production models for arid and semiarid regions, and using data from rainfall response surfaces, we provide a model of rangeland production. The arid and semiarid rangelands of South Africa present some unique challenges to range managers and graziers. In this article, we have highlighted but a few of these challenges, and in so doing have attempted to provide a refreshing view of the constraints to sustainable production of livestock.

Abstract: Frequent fire is a feature of the mesic Australian savannas, yet little is known about its effect on tree growth rates. Growth data are critical for the development of demographic models to understand the consequences of different land management regimes. We used generalized linear mixed effects models and information-theoretic multi-model inference to analyse annual diameter growth of adult trees (>=5 cm diameter at breast height, DBH) and saplings (>=1.5 m height and <5 cm DBH) and height growth of juveniles (<1.5 m height) in response to fire, tree size, stand basal area, annual rainfall, and for adult trees, the presence of the introduced Asian swamp buffalo (a potentially growth-limiting herbivore). The analysis was based on two medium-term datasets from natural eucalypt savanna in Kakadu National Park in the Australian monsoonal tropics. One dataset was based on a 7-year experiment examining the effect of buffalo removal during which three fires occurred, and the second was derived from a 4-year study in which three experimental fire treatments (annual early dry season fire, annual late dry season fire and no fire) were imposed. An unplanned, extremely severe fire burnt some of the previously unburnt trees in the final year of this latter experiment, so we considered it as an additional fire treatment. Despite high variance, there was strong evidence for differential effects of the fire treatments on tree growth, and these effects differed among the three size groups. Late and extreme fires resulted in a high proportion of individuals with negative DBH increments (due to burning or shedding of bark, and also to stems being killed and replaced by small stems), and decreased average DBH growth of saplings (-0.17 and -1.38 cm year-1, respectively--cf. 0.22 cm year-1 for no fire) and adult trees (0.01 and 0.03 cm year-1, respectively--cf. 0.18 cm year-1 for no fire). Early fires decreased DBH growth of saplings (0.11--cf. 0.22 cm year-1 for no fire) but increased growth of adult trees (0.29--cf. 0.18 cm year-1). Height growth of juvenile trees was reduced by early fires (0.01--cf. 0.06 m year-1 for no fire) but was increased by late fires (0.10 m year-1), probably because juveniles are physiologically active early in the dry season, but are effectively dormant in the late dry season. When stand basal area was high there was evidence of growth suppression in adults, saplings and juveniles. Growth of adult trees was lower in years with high rainfall and where buffalo were removed, possibly because of increased competition from ground layer vegetation. Our study casts doubt on the sustainability of the frequent, early dry season fires that have become a management goal in much of northern Australia.

Abstract: In Sahelian agro-ecosystems, sandy microdunes often provide a privileged habitat for primary production and can also be potential initial points for the regeneration of eroded surfaces. The aim of this study is to understand the role of sandy aeolian deposits in the retention of rain and runoff water on overgrazed Sahelian hillslopes. It focuses on the interactions between wind and water processes. Water is beneficial to the development of vegetation if it (i) infiltrates through soil surfaces; (ii) reaches a sufficient depth so that it does not rapidly evaporate; and (iii) is accessible to plant roots. In this study, the wetting-front depth (WFD) proved to be a relevant indicator of these three criteria. Investigations were conducted within three plots with surface area of 14,000, 376 and 36 m2 and grids of observations of 4, 0.5 and 0.2 m, respectively. The largest plot was a micro-catchment patched with sandy aeolian deposits. The two other plots were isolated microdunes with a typical asymmetric shape. A cone penetrometer was used to estimate the WFD and survey its spatial variability. Soil surface conditions (micro-relief, plant cover, crusted areas) were also estimated following the typology of Casenave and Valentin (Casenave, A., Valentine, C., 1992. A runoff capability classification system based on surface features criteria in semi-arid areas of West Africa. Journal of Hydrology 130, 231-249). At the catchment scale, WFD values ranged from 0-0.82 m. The deepest infiltration occurred within sandy deposits which supported an herbaceous cover of > 50% (drying surface type) and along rills filled with coarse sands (runoff surface type). Minimum WFD values were observed on bare crusted surfaces with gentle slopes (erosion surface type). At the microdune scale, the important penetration depths coincided with bare windward surfaces with steep slopes. This unexpected result seems to be due to the combined effect of wind deflation and splash erosion, which would hamper the development of impervious crusts. These results could have significant impacts for better understanding of rangeland sandy soil in semi-arid areas.

Abstract: This paper traces the history of grazing policy, its conceptual basis, practical implementations and outcomes, in three southern African countries. In spite of the divergent environmental conditions facing pastoralists in the Highlands of Lesotho, Botswana's southern Kalahari and the Namaqualand succulent karoo in South Africa, they have all been subjected to similar grazing and rangeland management policies. The theoretical underpinnings of such policies have their origins in a development paradigm and ecological theory derived from northern temperate environments and are directly related to two persistent and powerful narratives: [`]land degradation' and [`]the tragedy of the commons'. Policy and development initiatives were implemented in order to overcome the perceived causes of these negative scenarios, such as overstocking, open access tenure and low output subsistence production. They typically ignored the multi-purpose goals of traditional pastoral systems and emphasized commercialisation of livestock farming and privatisation of communal land, which resulted in the weakening or destruction of local, traditional land management institutions. Such policies have survived the transitions from colonial rule to independence and from apartheid to democracy. We argue that these powerful and pervasive ideas, when applied to grazing policies, have caused the very problems they were formulated to prevent.

Abstract: Grazing itineraries of herded and free grazing cattle (n = 194), goats (n = 148), and sheep (n = 129) were monitored in a village territory over a 1-year cycle by direct observation of grazing and excretion behaviour and by parallel animal tracking using a Global Positioning System. During the study period, standing and litter biomass of spontaneous vegetation and crop residues was measured repeatedly on sample plots of fields (n = 16), fallows (n = 15) and rangeland (n = 8). Based on a land use map, a Geographic Information System on forage availability was produced for the territory and overlaid with the livestock grazing itineraries. The animals' behaviour at pasture was related to the forage mass encountered along their daily itineraries in order to analyse the spatial variation in behaviour as influenced by season, livestock species and herd management mode. Maximum daily itinerary lengths were 25 km in cattle, 20 km in goats and 21 km in sheep; itinerary length varied significantly between species, herd management modes and season. Animals spent between 456 and 625 min per day on pasture, the grazing day of cattle being longer than that of sheep and goats. Across seasons, all three species spent on average about 60% of the daily grazing time feeding, 20-26% walking and 12-20% resting. The forage mass encountered along the animals' itineraries was higher than the average amount of forage available in the area. Particularly during the late dry and the rainy season, herding increased the amount of forage on offer to grazing livestock. Throughout the year, 39% of the observed excretions occurred on cropland, 31% on rangeland, 20% on fallows and 10% in and around settlements; the spatial repartition of excreta deposits differed between herded and free grazing animals, with free grazing animals depositing a higher share of excretions on barren land. The obtained information on the variation of grazing and excretion behaviour with respect to ruminant species, land use type, forage supply, season and herd management can be coupled with quantitative data on feed intake and excreta deposition, in order to compute livestock-mediated nutrient budgets for Sahelian agro-pastoral land use systems.

Abstract: Soil texture is an important influence on nutrient cycling in upland soils, with documented relationships between mineral particle size distribution and organic matter retention, nitrogen (N) mineralization, microbial biomass and other soil properties. However, little is known of the role of mineral particle size in riparian soils, where fluvial sorting creates strong spatial contrasts in the size distribution of sediments in sedimentary landforms. We studied total organic carbon (TOC) and total N (TN) storage and net N mineralization relative to soil texture and landform in soils of a riparian toposequence along the Phugwane River in Kruger National Park, South Africa. TOC, TN and potential N mineralization related strongly to particle size distribution in all soils along the toposequence. TOC and TN were positively correlated with silt and clay concentration (r2 =0.78). In long-term laboratory incubations, N mineralization was greatest in fine-textured, N-rich soils, although the proportions of soil N mineralized were inversely related to fine particle concentrations (r2=0.61). There were differences in TOC, TN and potential N mineralization among landform types, but none of these soil properties were statistically significant after accounting for the effect of particle size. These results demonstrate the influence of particle size in mediating N retention and mineralization in these soils. Predictable differences in soil texture across alluvial landforms contribute to corresponding contrasts in soil conditions, and may play an important role in structuring riparian soil and plant communities.

Abstract: Wildfire can lead to considerable hydrological and geomorphological change, both directly by weathering bedrock surfaces and changing soil structure and properties, and indirectly through the effects of changes to the soil and vegetation on hydrological and geomorphological processes. This review summarizes current knowledge and identifies research gaps focusing particularly on the contribution of research from the Mediterranean Basin, Australia and South Africa over the last two decades or so to the state of knowledge mostly built on research carried out in the USA. Wildfire-induced weathering rates have been reported to be high relative to other weathering processes in fire-prone terrain, possibly as much as one or two magnitudes higher than frost action, with important implications for cosmogenic-isotope dating of the length of rock exposure. Wildfire impacts on soil properties have been a major focus of interest over the last two decades. Fire usually reduces soil aggregate stability and can induce, enhance or destroy soil water repellency depending on the temperature reached and its duration. These changes have implications for infiltration, overland flow and rainsplash detachment. A large proportion of publications concerned with fire impacts have focused on post-fire soil erosion by water, particularly at small scales. These have shown elevated, sometimes extremely large post-fire losses before geomorphological stability is re-established. Soil losses per unit area are generally negatively related to measurement scale reflecting increased opportunities for sediment storage at larger scales. Over the last 20 years, there has been much improvement in the understanding of the forms, causes and timing of debris flow and landslide activity on burnt terrain. Advances in previously largely unreported processes (e.g. bio-transfer of sediment and wind erosion) have also been made. Post-fire hydrological effects have generally also been studied at small rather than large scales, with soil water repellency effects on infiltration and overland flow being a particular focus. At catchment scales, post-fire accentuated peakflow has received more attention than changes in total flow, reflecting easier measurement and the greater hazard posed by the former. Post-fire changes to stream channels occur over both short and long terms with complex feedback mechanisms, though research to date has been limited. Research gaps identified include the need to: (1) develop a fire severity index relevant to soil changes rather than to degree of biomass destruction; (2) isolate the hydrological and geomorphological impacts of fire-induced soil water repellency changes from other important post-fire changes (e.g. litter and vegetation destruction); (3) improve knowledge of the hydrological and geomorphological impacts of wildfire in a wider range of fire-prone terrain types; (4) solve important problems in the determination and analysis of hillslope and catchment sediment yields including poor knowledge about soil losses other than at small spatial and short temporal scales, the lack of a clear measure of the degradational significance of post-fire soil losses, and confusion arising from errors in and lack of scale context for many quoted post-fire soil erosion rates; and (5) increase the research effort into past and potential future hydrological and geomorphological changes resulting from wildfire.

Abstract: Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha- 1 yr- 1 and 0.7 to 4 Mg ha- 1 yr- 1 in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an holistic approach to sustainable management of these ecosystems. The ECBs of RMS ecosystems are not well understood. An ecosystem method of evaluating ECB of RMS ecosystems is proposed.

Abstract: We studied five lower forest-grassland ecotones in the Darhad Valley in northern Mongolia and investigated the effects of 20th Century grazing regimes and changes in grazing management on ecotone dynamics at a local scale. A total of 2968 Siberian larch (Larix sibirica) trees were cored and tree-age distribution was constructed to determine 20th Century tree establishment. Tree age and location within the ecotones were correlated and seedling density and their distribution were explored to describe forest-grassland ecotone shift. To examine livestock herbivory effects on ecotone shift, the number of new trees was analyzed with five different grazing regimes and changes in grazing practices during the last 80 years in the Darhad Valley. We documented some evidence of ecotone shift into the adjacent grassland. Rates and patterns of ecotone shift varied with different grazing regimes. Siberian larch tree establishment was greater at overall grazing intensities of low and high levels, which were dominated by sheep and cattle grazing. In contrast, larch establishment was lower at overall grazing intensities of low and medium levels, which were dominated by goat grazing. Twentieth Century changes in grazing practices also influenced Siberian larch regeneration. An abrupt decline in Darhad Valley larch establishment during the 20th Century coincided with locally increased grazing pressure. Furthermore, regional climate variability showed important interaction with local grazing regimes in affecting larch regeneration. A 20th Century pulse in larch establishment coincided with a time period of regionally known warmer temperatures and locally reduced grazing pressure. Our results suggest that overall grazing intensity, livestock species composition, and changes in grazing patterns are important in understanding grazing effects on Siberian larch tree encroachment.

Abstract: This paper revisits the debate over the relative effectiveness of [`]conservative' and [`]opportunistic' stocking strategies for African pastoral rangelands. The paper is based on a reassessment of the results of an earlier paper in this journal by Campbell et al. (2000) [Campbell, B.M., Dore, D., Luckert, M., Mukamuri, B., Gambiza, J., 2000. Economic comparisons of livestock production in communal grazing areas of Zimbabwe. Ecol. Econ., 33, 413-438] which argued that the advocacy of opportunistic strategies by the [`]new range science' was misplaced. This paper questions some of the assumptions of this scenario modelling effort, both in terms of causal structure and parameter estimates. By developing a mimic model and using data from the same site-a dryland communal area in southern Zimbabwe-this paper shows how the conclusions of the earlier paper were premature. The need for sensitivity analysis in assessing model findings is emphasised if policy conclusions, with potentially major impacts on people's livelihoods, are to be drawn. A brief discussion of the implications of this reassessment, including more broadly the limitations and prospects of economic-ecological modelling in policymaking for rangeland management, concludes the paper.

Abstract:

Abstract: Success in long-term agricultural production in resource-poor farming systems relies on the efficiency with which nutrients are conserved and recycled. Each transfer of nutrients across the farming system provides a risk of inefficiency, and how much is lost at each step depends on the type of farming system, its management practices and site conditions. The aim of this review was to identify critical steps where efficiency of nitrogen (N) cycling through livestock in smallholder crop-livestock farming systems could be increased, with special emphasis on Africa. Farming systems were conceptualised in four sub-systems through which nutrient transfer takes place: (1) livestock: animals partition dietary intake into growth and milk production, faeces and urine; (2) manure collection and handling: housing and management determine what proportion of the animal excreta may be collected; (3) manure storage: manure can be composted with or without addition of plant materials and (4) soil and crop conversion: a proportion of the N in organic materials applied to soil becomes available, part of which is taken up by plants, of which a further proportion is partitioned into grain N. An exhaustive literature review showed that partial efficiencies have been much more commonly calculated for the first and last steps than for manure handling and storage. Partial N cycling efficiencies were calculated for every sub-system as the ratio of nutrient output to nutrient input. Estimates of partial N cycling efficiency (NCE) for each sub-system ranged from 46 to 121% (livestock), 6 to 99% (manure handling), 30 to 87% (manure storage) and 3 to 76% (soil and crop conversion). Overall N cycling efficiency is the product of the partial efficiencies at each of the steps through which N passes. Direct application of plant materials to soil results in more efficient cycling of N, with fewer losses than from materials fed to livestock. However, livestock provide many other benefits highly valued by farmers, and animal manures can contain large amounts of available N, which increases the immediate crop response. Manures also can contribute to increase (or at least maintain) the soil organic C pool but more quantitative information is needed to assess the actual benefits. Making most efficient use of animal manures depends critically on improving manure handling and storage, and on synchrony of mineralisation with crop uptake. Measures to improve manure handling and storage are generally easier to design and implement than measures to improve crop recovery of N, and should receive much greater attention if overall system NCE is to be improved.

Abstract: Vegetation changes are documented from a well-dated pollen record from Lake Emakat, Empakaai Crater, northern Tanzania. This pollen record includes the time interval covering the Pleistocene/Holocene transition, analysed at a resolution interval averaging 200 yr. Around the crater lake, an Hagenia-forest development starting at 14,500 cal yr BP lasted until 13,000 cal yr BP. A change in vegetation, indicated by an increased proportion of Nuxia congesta in the forest and Artemisia in the afro alpine grassland after 13,000 cal yr BP, corresponds in time to the Northern Hemisphere's Younger Dryas cooling. Grasses and sedges increased at ~ 10,100 cal yr BP, indicating a significant increase in local pollen possibly attributed to lowered lake level, related to drier conditions. Although the Empakaai pollen record documents continuous forest conditions, from 14,500 to 10,100 cal yr BP, the variation in the proportion of forest components seem to respond to environmental changes at the millennium scale.

Abstract: We report five Oligocene-early Miocene pollen assemblages from the Loperot-1 exploration well drilled in the semi-desert Lokichar Basin (latitude 02° 21' 46.15'' N, longitude 35° 52' 23.47'' E, ground elevation 615 m above MSL), near Lake Turkana in northern Kenya. They represent the second oldest plant microfossils so far recovered from East Africa and add significantly to the Paleogene-Neogene tropical African fossil plant record. The Loperot pollen indicate a mosaic environment of semi-deciduous forest and humid woodland whose floristic composition presents strong affinities with the vegetation occurring today in the Guinea-Congolia/Zambezia phytogeographical transition zone, with a rainfall more than 1000 mm/year and a well defined dry season. The weak representation of Poaceae and herbaceous taxa characteristic of grassland, dry bushland or savanna and the abundance of shade tolerant plants such as ferns all point to a vegetation composed to a variety of communities with closed forest formations predominant. The lack of typical temperate mountains elements, mainly Podocarpus and Juniperus today widespread on the East African highlands, indicates that the geography of the region was different from that of today. The plateaux or uplands adjacent to the Lokichar basin were probably still not high enough during this period of early rifting in East Africa to support the temperate coniferous forests characteristic of the Plio-Pleistocene.

Abstract: Abstract 10.1002/ldr.692.abs Rapid population growth, unsustainable land use, and a pervasively degrading landscape are components of a dominant paradigm regarding African development. While recent work articulating the �misreading� of the African landscape have begun to challenge this paradigm, much work remains regarding the pervasiveness and character of this misread. A method is presented for investigating mechanisms of land-cover change that combines remotely sensed data, archival data, and rapid appraisals in a way less influenced by dominant paradigms. We present a case where increasing human activity is resulting in accumulation of woody biomass on edaphic grasslands of a forest�grassland mosaic, rather than the expansion of grasslands at the expense of forests as is currently understood in that area. These increases in biomass are stimulated by anthropogenic influences that are shaped by institutional and edaphic factors. We do not claim that resources are being pervasively enhanced across sub-Saharan Africa under conditions of population growth, but that there may be many mechanisms of change, resulting in both degradation and enhancement, occurring simultaneously across sub-Saharan Africa or even intra-regionally within a nation under these conditions. The integration and application of these methods serve to improve applied analyses of land-cover change to better characterize these mechanisms, and avoid the wrong policy prescriptions. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract: South Africa is unique in that its globally significant biodiversity, which is under significant threat, coexists with an apartheid history of dispossession that produced a starkly unequal land ownership pattern and widespread rural poverty. It is in this context that the post-apartheid government must fulfil constitutional and international obligations to safeguard environmental assets as well as undertake land reform benefiting the previously dispossessed. Consequently, there is a continuous challenge of reconciling complex and often conflicting relationships between poverty, inequitable access to resources, and the protection of biodiversity. Current efforts to conserve the Cape Floral Kingdom emphasize partnerships between private landowners and existing nature reserves to promote sustainable utilisation of biodiversity. This paper presents a case study exploring how this approach might be reconciled with land rights and opportunities for land-based livelihoods among farm dwellers in the Baviaanskloof area of the Eastern Cape. The paper identifies systemic and structural tensions in current attempts to reconcile biodiversity conservation and farm dwellers 039; interests, and documents issues of process and principle that could become important in the future. In doing so, it highlights the influence of on-farm power relations and overly complex institutional arrangements in determining the real extent of participation by affected farm dwellers and the efficacy of social safeguard policies. Findings also caution against an over-reliance on ecotourism as the major occupation and the paper argues instead for support for multiple livelihood strategies.

Abstract: Traditional vegetative techniques to control gully development rely mainly on the effects of above ground biomass, whereas little attention has been given to the role of below ground biomass. Yet, in a context where above ground biomass may temporarily or spatially disappear (e.g. due to fire or grazing), roots can play an important role in protecting soil against erosion. Few studies have investigated the impacts of roots of natural vegetation (such as grass) on the resistance of topsoils in concentrated flow erosion zones, although grasses grow in many environments. Therefore, the objective of this study is to investigate the impact of root density and root length density of grass on the erodibility of root-permeated saturated topsoils. Three plots were established on a sandy loam. Their treatments were (1) bare, (2) low density drilled grass and (3) high density drilled grass, simulating different root densities. After one month, topsoil samples were taken and subjected to concentrated flow using a hydraulic flume in the laboratory. Slope, flow discharge, mean velocity, water temperature and sediment concentration were measured. Root density and root length density values were assessed. Relative soil detachment rates and mean flow shear stresses were calculated. The results indicate a negative exponential relation between the relative soil detachment rate and root density as well as root length density, independent of the applied flow shear stresses. However, the best relationship fitting the data is the Hill curve, indicating that relative soil detachment rates decrease to very low values (0.05) with an increase in root density from 0 to 4 kg m- 160;3 or root length density from 0 to 400 km m- 160;3. A comparison between the effects of vegetation cover on sheet and rill erosion rates and those of the root area ratio of grass roots on relative soil detachment rates reveals that grass roots are very effective in reducing soil detachment rates. The equations obtained can be used to predict the effect of grass roots on soil erosion rates during concentrated runoff and to evaluate the ability of roots to increase topsoil resistance against erosion by concentrated flow. Calculations of relative erosion rates using the equations from the RUSLE and WEPP models indicate that the observed trend is better predicted with the RUSLE model and the WEPP model for croplands than with the WEPP model for rangelands.

Abstract: Traditional vegetative techniques to control gully development rely mainly on the effects of above ground biomass, whereas little attention has been given to the role of below ground biomass. Yet, in a context where above ground biomass may temporarily or spatially disappear (e.g. due to fire or grazing), roots can play an important role in protecting soil against erosion. Few studies have investigated the impacts of roots of natural vegetation (such as grass) on the resistance of topsoils in concentrated flow erosion zones, although grasses grow in many environments. Therefore, the objective of this study is to investigate the impact of root density and root length density of grass on the erodibility of root-permeated saturated topsoils. Three plots were established on a sandy loam. Their treatments were (1) bare, (2) low density drilled grass and (3) high density drilled grass, simulating different root densities. After one month, topsoil samples were taken and subjected to concentrated flow using a hydraulic flume in the laboratory. Slope, flow discharge, mean velocity, water temperature and sediment concentration were measured. Root density and root length density values were assessed. Relative soil detachment rates and mean flow shear stresses were calculated. The results indicate a negative exponential relation between the relative soil detachment rate and root density as well as root length density, independent of the applied flow shear stresses. However, the best relationship fitting the data is the Hill curve, indicating that relative soil detachment rates decrease to very low values (0.05) with an increase in root density from 0 to 4 kg m- 160;3 or root length density from 0 to 400 km m- 160;3. A comparison between the effects of vegetation cover on sheet and rill erosion rates and those of the root area ratio of grass roots on relative soil detachment rates reveals that grass roots are very effective in reducing soil detachment rates. The equations obtained can be used to predict the effect of grass roots on soil erosion rates during concentrated runoff and to evaluate the ability of roots to increase topsoil resistance against erosion by concentrated flow. Calculations of relative erosion rates using the equations from the RUSLE and WEPP models indicate that the observed trend is better predicted with the RUSLE model and the WEPP model for croplands than with the WEPP model for rangelands.

Abstract: Extensive research exists on the effects of Canada thistle [Cirsium arvense (L.) Scop.] (CT) in annual cropland, but few studies have examined CT impacts on pasture and rangeland. While it is known that grazing impacts weed presence and abundance, little is understood about how specific grazing systems can be used as a prescriptive tool to alter weed populations, including CT. The purpose of this study was to experimentally test three cattle grazing systems, including (1) continuous or season-long grazing (SL), (2) short duration (SD) (or low intensity-high frequency) rotational grazing, and (3) high intensity-low frequency (HILF) rotational grazing, for their ability to reduce CT and release non-CT herbage within permanent pastures of central Alberta, Canada. A secondary objective was to evaluate season-long changes in the quality of CT shoots as potential forage throughout the growing season. Results showed that SL grazing maintained or increased severe CT infestations and reduced forage yield. In contrast, the HILF rotational system reduced CT shoot density and biomass, as well as flowering, and resulted in greater weed suppression than the SD system. Two intense defoliations annually over 2-3 years nearly eliminated CT stems. Remaining CT shoots were also primarily vegetative and greater in forage quality under HILF grazing. As a weed biological control tool for CT, prescribed grazing with an HILF system may be particularly important in areas where other control options, including the use of herbicides, are not possible due to environmental restrictions or inaccessibility to equipment.

Abstract: Nineteen months of continuous data from two sites within the atmospheric boundary layer experiments (ABLE) facility are used to compare surface energy fluxes, carbon dioxide fluxes and controlling parameters. One site, which has been monitored continuously since 1997, is rangeland, with a mixture of C3 and C4 grasses. The other site is active cropland that was planted in sorghum for the first growing season of the observation period and in winter wheat for the second. The uptake of carbon dioxide was well-defined within the respective growing seasons, with peak uptake rates for sorghum being greater by almost a factor of 2 than those for wheat and rangeland. The longer growing season for rangeland almost countered this effect. Net production of carbon dioxide occurred at both sites at the beginning and end of the growing seasons because of root growth respiration and enhanced decay of tilled soil.

Abstract: Plant, water, and soil components of the Simulation of Production and Utilization of Rangelands model (SPUR 2.4) were incorporated into the Integrated Farm System Model (IFSM 1.2) to represent the growth and competition of multiple plant species in pastures and their effects on pasture productivity and botanical composition in temperate climates. Developed for semi-arid rangelands, SPUR required major adjustment to represent temperate pastures adequately. In particular, the effects of soil moisture on root and shoot mortality and photosynthetic rates were adjusted to represent greater susceptibility of temperate plants to drought. Sensitivity analysis showed that predicted total shoot dry matter appeared most sensitive to photosynthesis and growth parameters in the spring, soil moisture parameters in the summer, and senescence parameters in autumn. Across all seasons, shoot dry matter appeared most sensitive to optimum photosynthetic temperatures, specific leaf area, start and end dates of senescence, maximum nitrogen concentration in live shoots, and a maximum shoot specific growth rate. The revised pasture model incorporated into IFSM was calibrated with 2002 field data from experimental pastures in central Pennsylvania, USA containing primarily orchardgrass (Dactylis glomerata) and white clover (Trifolium repens). Predictive accuracy of the model was then further evaluated by comparing 2003 data from the same pastures to simulated production. The integrated submodel predicted soil water content and dry matter production relatively well. It did not achieve a desired degree of accuracy in predicting the dynamics of botanical composition; however, adjustment of SPUR subroutines to allow variable maximum root:shoot ratios and competition for light and water may improve predictions. Further development and use of this integrated model can help researchers improve their understanding of temperate pasture systems, identify gaps in knowledge, and prioritize future research needs. Ultimately, the integrated model could provide more accurate assessment of the influence of management strategies on pasture productivity, animal production, and economics at the whole-farm scale.

Abstract: We discuss the search for optimal stocking regimes in semi-arid grazing lands. We argue that [�]one size does not fit all 039; and that different stocking regimes are appropriate under different conditions. This paper is an attempt to move beyond polarization of the current debate towards a more integrative and flexible approach to grazing management. We propose five different conditions as major influences on grazing regimes: environmental variability and predictability; degradation and thresholds; property right regimes; discount rates; and market stability and prices. We suggest a lack of connection between the micro-economics literature and natural science and social-anthropological literature. It is timely to achieve greater integration around some key questions and hypotheses, and recognize that policy prescriptions at national or even regional levels are likely to have limited value due to context specificity.

Abstract: The Drakensberg Alpine Centre (DAC) of southern Africa supports a speciose number of angiosperms. Its compliment of 2520 native angiosperms is comparable with the native floras of northern hemisphere countries such as Germany or Switzerland, and is almost double that of Great Britain. Levels of angiosperm endemism and near-endemism in the DAC too are high, that are here treated within a conservation framework to draw attention to the local and global significance of its biodiversity. The DAC supports some 334 endemic and 595 near-endemic angiosperms, meaning that almost 37% if its flora is confined to a core region south of the Limpopo River. Strict endemism is c. 13%, slightly lower than the 16% endemism for KwaZulu-Natal, and substantially lower than endemism (c. 69%) in the Cape Floristic Region. Most endemic and near-endemic taxa belong to the Asteraceae, Scrophulariaceae and Iridaceae, which are the largest, fourth largest and seventh largest angiosperm families in the DAC respectively. Helichrysum and Senecio contribute the most endemics and near-endemics. Many of the endemics are rare, and have very specific habitat preferences. Some 42% of the endemic taxa, and 16% of the near-endemic taxa, are Red Data species. Here we add a further 42 endemic taxa (c. 13%) to the Orange List, bringing the total number of endemics that are now either Red or Orange Data listed to 182 (c. 55%); their conservation needs to be prioritised. A strong plea is made for the continued sustainable management and protection of biota in the DAC, and the mitigation of any threats that may lead to their demise.

Abstract: South Africa 039;s winter-rainfall zone is a climatically sensitive region, lying at the interface of the earth 039;s temperate and sub-tropical climatic systems. Its seasonally arid climate has generally prevented the preservation of long and organic-rich sedimentary deposits, producing a spatially limited and temporally biased Quaternary record. This paper seeks to address this issue further and develop a fuller understanding of the wider climatic changes in this region during the Late Quaternary. Modern climatic data does not support the definitions of the 34;winter-rainfall zone 34; presented in previous syntheses and this factor, amongst others, may explain difficulties in resolving the palaeoenvironmental record in this region. We present palaeoenvironmental evidence from the Agulhas Plain, an area marginal to the modern winter-rainfall zone. Cored sedimentological and palynological records from two pans are integrated with previously reported records of aeolian activity, providing evidence for phases of enhanced aridity and humidity during the Late Quaternary. The record is fragmentary, which may reflect the cycling of sediment between the pans and their accompanying lunette dunes. Lacustrine sedimentary sequences dating to c. 33 ka - 62; 160;47 ka provide evidence for enhanced humidity consistent with evidence in the winter and year-round rainfall zones. Increased humidity is also recorded from c. 2 160;ka, following drier conditions than the present c. 2.7-2.5 160;ka. Palynological evidence supports the sedimentological interpretations of pan water status and offers rare insights into the nature of the region 039;s unique Fynbos vegetation during the Late Pleistocene.

Abstract: The intrinsic value of soil to national, regional and local agroecological and economic productivity in sub-Saharan Africa is not adequately manifest in financial planning and decision making, challenging long-term sustainability as that resource degrades. While efforts to internalize the external costs of soil erosion in monetary units are available in the literature, we offer an alternative approach based on emergy synthesis, which enumerates the value of soil based on the environmental work required to produce it rather than based on surveys or derived pricing techniques. Emergy synthesis integrates all flows within a system of coupled economic and environmental work in common biophysical units (embodied solar energy or solar emjoules�sej), facilitating direct comparisons between natural and financial capital. Insight into long-term sustainability of human economic production and its basis in natural capital stocks is achieved via a suite of emergy-based indices. Our objective was to provide context for the magnitude of soil erosion losses within the larger resource basis of the Kenyan economy at three scales. Our results suggest that erosion losses at the national scale (4.5E21 160;sej/yr) are equal in magnitude to national electricity production or agricultural exports (equivalent to $ 390 million annually or 3.8% of GDP). This significant hidden, long-term cost is magnified in the selected district economies. In particular, in Nyando district (a densely populated rural district in western Kenya) we estimate that soil erosion represents over 14% of total emergy flows. The soil intensity of agriculture (SIA 160;= 160;agricultural yield/soil loss, both in emergy units) of Nyando (2.25) illustrates a severely marginalized agricultural sector in comparison with the nation as a whole (SIA 160;= 160;7.56) or other nations (SIAUSA 160;= 160;81.9, SIABrazil 160;= 160;15.6). Soil loss measurements across land uses typical in western Kenya allowed emergy evaluation of differential costs and benefits; soil loss represented between 12 and 62% of total emergy use (subsistence agriculture SIA 160;= 160;8.13, communal rangeland SIA 160;= 160;1.62). By quantifying the ecological costs of soil erosion in units directly comparable with flows in other sectors of the economic system, we provide a baseline measure of sustainability against which appropriate investment (i.e., scaled to problem magnitude, targeted to hot-spots) in soil conservation may be evaluated.

Abstract: Summary Daily runoff depths from 28 plots (5 160;m 160; 215; 160;2 160;m) recorded during a 2-year period in the semi-arid to subhumid highlands of Tigray were analyzed to study the effect of vegetation restoration in exclosures and to identify other factors influencing runoff production. Plots are distributed over three study sites and located in different land use types and on different combinations of soil type, vegetation cover and slope gradient. Runoff was found to be significantly reduced when a degraded area is allowed to rehabilitate after closure. Runoff depth is significantly correlated with event variables such as rain depth, rainfall intensity, storm duration and soil moisture content. Total vegetation cover is the most important plot variable explaining about 80% of the variation in runoff coefficients through an exponential decay function. Also the runoff generating rainfall threshold has a positive correlation with total vegetation cover. Runoff was found to be negligible when the vegetation cover exceeds 65%. Other important variables affecting runoff production in the study sites are soil organic matter, soil bulk density, litter cover and slope gradient.

Abstract: In the Tigray highlands of Northern Ethiopia, the establishment of exclosures (i.e., areas closed for grazing and agriculture) has become an important measure to combat land degradation and restore vegetative cover. Exclosures are commonly found on steep slopes and downslope from a sediment source area. In this study their sediment trapping capacity and controlling factors were investigated. Total sediment depth turned out to be related to vegetation cover, sediment source area and in some cases slope gradient. Thickness of recent, short-term ( 60; 160;20 years) sediment deposits was strongly related to distance from the top edge of the closed area, slope gradient, vegetation cover and characteristics of the sediment source area. Mean sediment deposition rates ranged between 26 and 123 Mg ha- 160;1 yr- 160;1. Under influence of vegetation and sediment deposition dark soils rich in organic matter (Phaeozems) develop. In view of their high sediment trapping capacity, exclosures are highly valued as efficient soil conservation measures in the Tigray highlands.

Abstract: Tropical African climate has oscillated between markedly wetter and drier conditions on all timescales in response to global climate disturbances. A step-like increase in aridity over the past 3 160;Ma has been primarily paced by orbital cycles coupled with the onset and amplification of high-latitude glacial cycles. On the 104-103-ka timescales, observed changes imply interactions between insolation, sea-surface conditions and vegetation. High-frequency variations could be linked to oscillations in major atmospheric circulation modes, in solar output, or to major volcanic events. To cite this article: F. 160;Gasse, C. 160;R. Palevol 5 (2006).

Abstract: Precipitation is considered to be the primary resource limiting terrestrial biological activity in water-limited regions. Its overriding effect on the production of grassland is complex. In this paper, field data of 48 sites (including temperate meadow steppe, temperate steppe, temperate desert steppe and alpine meadow) were gathered from 31 published papers and monographs to analyze the relationship between above-ground net primary productivity (ANPP) and precipitation by the method of regression analysis. The results indicated that there was a great difference between spatial pattern and temporal pattern by which precipitation influenced grassland ANPP. Mean annual precipitation (MAP) was the main factor determining spatial distribution of grassland ANPP (r2 = 0.61, P 60; 0.01); while temporally, no significant relationship was found between the variance of ANPP and inter-annual precipitation for the four types of grassland. However, after dividing annual precipitation into monthly value and taking time lag effect into account, the study found significant relationships between ANPP and precipitation. For the temperate meadow steppe, the key variable determining inter-annual change of ANPP was last August�May precipitation (r2 = 0.47, P 60; 0.01); for the temperate steppe, the key variable was July precipitation (r2 = 0.36, P = 0.02); for the temperate desert steppe, the key variable was April�June precipitation (r2 = 0.51, P 60; 0.01); for the alpine meadow, the key variable was last September�May precipitation (r2 = 0.29, P 60; 0.05). In comparison with analogous research, the study demonstrated that the key factor determining inter-annual changes of grassland ANPP was the cumulative precipitation in certain periods of that year or the previous year.

Abstract: Trachypogon savannas in Venezuela are mainly used for extensive cattle raising. These savannas are currently affected with man-made or natural fires. During fires, 24% of the nitrogen (N) necessary for primary production is lost through volatilisation. More is lost by leaching and/or erosion. Since those losses are not compensated for by N input through precipitation, N balance in these savannas depends on biological mechanisms. In this study we explore the possible forms of biological N fixation, in particular the cyanobacterial activity from soil microbial crusts, and the contribution of grass rhizosphere microorganisms. Determinations were made by using, in situ, the method of acetylene reduction as an estimate of nitrogenase activity (NA). N2 fixation due to NA in the soil-plant system is 13.7 and 7.8 160;kg ha-1 year-1 for the burned and protected plots, respectively. Even considering the lowest fixation values by microbial crusts, they could provide 6% of the N needed for annual production of the vegetation of the savanna under fire, and 9% in the protected savanna. These amounts of N2 sustained the productivity of the vegetation experiencing periodical fires.

Abstract: Large amounts of viable seeds from Mediterranean grassland species have been found in herbivore dung; however which species produce seeds that can survive and germinate after ingestion by herbivores is still not well understood. This paper evaluates the importance of seed size, shape and coat impermeability in the endozoochorous dispersal process of 20 abundant species from central Iberian rangelands. Seed survival, germination percentages and germination speed were analysed in controlled experiments on the chewing and gut passage process by inserting seeds in the rumen of fistulated sheep, followed by simulated acid-pepsin digestion. Higher germination percentages in the control than the simulated sheep ingestion treatment were found in 75% of seeds. All species showed lower survival following the treatment, two species had a higher germination speed and five had a lower rate. Large-seeded species generally had higher survival percentages than small-seeded species. Species with impermeable seed coats had higher germination percentages following treatment although no significant differences were noted for either seed survival or germination speed.

Abstract: Invasion by alien species is threatening the conservation of native plant communities and the integrity of ecosystems. To gain a better understanding of such impacts, many studies have examined the traits that make alien species successful invaders as well as the factors involved in community invasibility. However, it is necessary to link invader effects on community structure and on ecosystem processes in order to unravel the mechanisms of impact. Cortaderia selloana is a perennial grass native to South America that is invading abandoned agricultural lands close to coastal human settlements in Catalonia (NE Spain). In invaded pastures, we examined the association between C. 160;selloana invasion, soil properties and vegetation structure changes in pastures, comparing the neighbourhood area of influence of C. 160;selloana with areas far from C. 160;selloana. Areas under the influence of C. 160;selloana had lower total soil nitrogen values and higher C/N values than in areas far from C. 160;selloana. Furthermore, the areas affected by C. 160;selloana had lower species, family and life form richness and diversity, and less plant cover. In addition, C. 160;selloana also increased the vertical vegetation structure and changed species composition (only 44% similarity between invaded and non-invaded areas). Our results point out that C. 160;selloana has an effect on its neighbourhood leading to an increase in small-scale variability within invaded fields.

Abstract: The distribution of pollen in marine sediments is used to record vegetation change on the continent. Generally, a good latitudinal correspondence exists between the distribution patterns of pollen in the marine surface sediments and the occurrence of the source plants on the adjacent continent. To investigate land-sea interactions during deglaciation, we compare proxies for continental (pollen assemblages) and marine conditions (alkenone-derived sea surface temperatures) of two high-resolution, radiocarbon-dated sedimentary records from the tropical southeast Atlantic. The southern site is located West of the Cunene River mouth; the northern site is located West of the Angolan Huambe Mountains. It is inferred that the vegetation in Angola developed from Afroalpine and open savannah during the last Glacial maximum (LGM) via Afromontane Podocarpus forest during Heinrich Event 1 (H1), to an early increase of lowland forest after 14.5 160;ka. The vegetation record indicates dry and cold conditions during the LGM, cool and wet conditions during H1 and a gradual rise in temperature starting well before the Younger Dryas (YD) period. Terrestrial and oceanic climate developments seem largely running parallel, in contrast to the situation ca. 5 176; further South, where marine and terrestrial developments diverge during the YD. The cool and wet conditions in tropical West Africa, South of the equator, during H1 suggest that low-latitude insolation variation is more important than the slowdown of the thermohaline circulation for the climate in tropical Africa.

Abstract: We use a simple ecological sustainability simulator (SESS) [Diaz-Solis, H., Kothmann, M.M., Hamilton, W.T., Grant, W.E., 2003. A simple ecological sustainability simulator (SESS) for stocking rate management on semi-arid grazinglands, 76, 655] for rangelands with mean annual precipitation of 500 160;mm to evaluate tendencies in range productivity and cattle production under four management options: (1) supplemental feeding, (2) short-term reduction of stocking rate, (3) early weaning, and (4) adjustment of breeding seasons. We have made five modifications to SESS for the present paper. (1) Cattle mortality now occurs each month as a function of body condition. (2) Cows that are not pregnant 2 months after the end of the breeding season are sold. (3) Forage intake is calculated separately for each cohort of cows. (4) Cows that have been sold or have died are replaced just before the beginning of each breeding season (except for the short-term reduction of stocking rate strategy). (5) The calculation of stocking rate now includes cows, bulls, nursing calves, weaned heifers less than 20 months of age, and pre-reproductive heifers aged 20 months or older. Simulation results suggest the four management options might be ranked from best to worst, in terms of increasing cattle production while maintaining range productivity, as: (1) short-term reduction of stocking rate, (2) adjustment of breeding seasons, (3) early weaning, and (4) supplementation. Short-term reduction of high stocking rates reduces the deterioration of range productivity because of the reduction in the number of stock. Adjustment of breeding seasons such that periods of highest energy requirements of cows and calves coincide with periods of highest forage production increases percentage pregnancy. Early weaning of calves improves the body condition of cows and increases annual production of weaned calves, but does not reduce the stocking rate and thus does not improve range productivity. Supplemental feeding, and other management practices that artificially sustain herbivores, break the negative feedback that promotes good range productivity and maintains long-term system stability. In general, strategies to increase cattle production in semi-arid rangelands should be based on the improvement of natural forage production.

Abstract: Ceropegia macmasteri, a new species from Cathcart in the Eastern Cape Province of South Africa, is only known from a single population in Dohne sourveld grassland where it occurs with another rare local endemic species of the Ceropegieae, Brachystelma cathcartense R.A.Dyer. The new species, an herbaceous grassland plant with a tuberous rootstock, most closely resembles C. stentiae E.A.Bruce, but is distinguished by its linear-erect corona lobes and inner corona conniving to form a central column.

Abstract: The multiple benefits from livestock production to rural households are evaluated in Thorndale, a communal area of the Limpopo Province South Africa. Monetary values of livestock products are presented. Values from most previous studies are static (and thus outdated), as a result of conceptual and methodological shifts. The net monetary value of the direct benefits from livestock was estimated as $656 per household/annum, excluding the holding of cattle for savings. The net value is equivalent to 22.7% of the value of the other livelihood sources that were considered, and inclusive of cash income streams, crops, and secondary woodland resources. A net 168% herd increase in livestock was recorded between 1993 and 1999. More households owned goats compared to cattle, and cattle were important for use as draught power, and for milk. Households without livestock benefited through gifts and services, valued at $33 per household/annum. Policy concerns are the provision of adequate market and pricing mechanisms for communal area livestock, tailored savings, investment support, credit schemes, and infrastructure. An appropriate multipurpose benefit production model, other than a commercialised model is suggested for the sector.

Abstract: Five experiments investigated the importance of herbivory by Sminthurus 160;viridis in structuring botanical composition in developing grasslands, and how these effects may be modified by diversity in collembolan and plant species. Differential susceptibility to S. 160;viridis feeding was demonstrated in 23 dicotyledonous and three monocotyledonous plants assayed as seedlings at the first true leaf stage. The composition of seedling communities developing from natural and artificially constructed soil seed banks varied with the level of S. 160;viridis infestation, with plant species least susceptible to herbivory making the greatest contribution to plant biomass. The combined effect of herbivory by S. 160;viridis and Bourletiella 160;hortensis on Trifolium 160;repens biomass was shown to be less than the effect of S. 160;viridis alone, indicating competitive interference. The adverse effects of herbivory by S. 160;viridis on T. 160;repens biomass was reduced by increased diversity of plants growing in association with the legume, and the presence of four non-herbivorous arthropleonan Collembola. S. 160;viridis was shown to reduce seedling numbers, species diversity and biomass in communities developing from the soil seed bank, but the presence of non-herbivorous arthropleonan species reduced the effect of S. 160;viridis. The experiments demonstrate the potential for herbivory by S. 160;viridis to significantly alter species composition in developing grassland communities. However, interactions with collembolan and plant species profoundly modified S. 160;viridis herbivory impacts, either by reducing feeding intensity or enhancing plant growth. These results highlight the fact that data from simple, synthetic systems may be poor predictors of herbivory impacts under field conditions where more complex species interactions occur.

Abstract: Large herbivores can both positively and negatively affect primary productivity and rates of nutrient cycling in different ecosystems. Positive effects of grazers in grasslands have been attributed to migratory behavior of the dominant ungulate species and soil fertility. We studied the effects of grazers on aboveground net primary productivity (ANPP) and N cycling on central Kenyan rangeland characterized by intense, chronic grazing by a mixed community of cattle and resident native ungulates. Exclosure studies conducted at high and low levels of soil fertility showed that both soil fertility and annual rainfall patterns mediate the effects of grazers on ANPP and N cycling. In a low-rainfall year with short (1 month) growing seasons, grazers reduced aboveground productivity regardless of soil nutrient availability. However, in a high-rainfall year with a 5-month growing season, grazers increased ANPP on nutrient-rich glades and suppressed ANPP on nutrient-poor bushland sites. Concomitant studies of grazer effects on N cycling revealed complex interactions with the seasonal pattern of N-mineralization and inorganic N availability. Grazers increased the size of the inorganic N pool available to plants at the onset of the growing season, particularly in nutrient-rich glades. However, grazers also decreased N mineralization rates at all sites early in the growing season. Measures of N availability via ion-exchange resin bags suggested that the combined effects of grazers on inorganic N pool fluctuations and N-mineralization rates resulted in a net increase in N availability at glade sites and a net decrease in N availability at bushland sites. The net effect of grazers on soil N availability mirrored grazer effects on ANPP in the high-rainfall year. Overall, our results suggest that grazer effects on N dynamics are closely linked to effects on productivity and resilience to drought. Furthermore, even under optimal conditions of high soil fertility and above-average rainfall, grazer promotion of ANPP in this chronically grazed system dominated by resident ungulates was small compared to systems dominated by migratory ungulates.

Abstract: Study of soil property variations resulting from topographic aspect and vegetation changes will have implication on the proper management of marginal and environmentally sensitive areas. This study addressed the effects of topographic aspect and vegetation community types on soil physical and chemical properties in the Bale Mountains, south-eastern highlands of Ethiopia. At each stratified vegetation community; Schefflera-Hagenia, Hypericum-Erica-Schefflera, and Erica arborea (shrub size), and in each of the four topographic aspects, four representative soil profiles giving a total of 3 � 4 � 4 = 48 were opened and described. Soil texture, bulk density, soil pH, plant available phosphorus, CEC, exchangeable base cations, and percent base saturations were analyzed and interpreted. Except in few cases, all considered soil properties showed significant differences among vegetation communities and topographic aspects. The differences may be attributed to leaching and differences in organic matter (carbon) contents within the soil profiles due to topographic aspect-induced microclimatic differences, reflecting the response of vegetation communities to the conditions. Soil textural fractions, mainly silt and clay, bulk density, pH, plant available phosphorus, percent base saturation, CEC, and exchangeable base cations generally increased in the Schefflera-Hagenia vegetation community zone. Further studies might be required to fully understand and clarify the influence of aspect, topography and vegetation types on soil properties for site-specific soil resource management practices in this mountainous area.

Abstract: Traditional vegetative techniques to control gully development rely mainly on the effects of above ground biomass, whereas little attention has been given to the role of below ground biomass. Yet, in a context where above ground biomass may temporarily or spatially disappear (e.g. due to fire or grazing), roots can play an important role in protecting soil against erosion. Few studies have investigated the impacts of roots of natural vegetation (such as grass) on the resistance of topsoils in concentrated flow erosion zones, although grasses grow in many environments. Therefore, the objective of this study is to investigate the impact of root density and root length density of grass on the erodibility of root-permeated saturated topsoils. Three plots were established on a sandy loam. Their treatments were (1) bare, (2) low density drilled grass and (3) high density drilled grass, simulating different root densities. After one month, topsoil samples were taken and subjected to concentrated flow using a hydraulic flume in the laboratory. Slope, flow discharge, mean velocity, water temperature and sediment concentration were measured. Root density and root length density values were assessed. Relative soil detachment rates and mean flow shear stresses were calculated. The results indicate a negative exponential relation between the relative soil detachment rate and root density as well as root length density, independent of the applied flow shear stresses. However, the best relationship fitting the data is the Hill curve, indicating that relative soil detachment rates decrease to very low values (0.05) with an increase in root density from 0 to 4 kg m- 3 or root length density from 0 to 400 km m- 3. A comparison between the effects of vegetation cover on sheet and rill erosion rates and those of the root area ratio of grass roots on relative soil detachment rates reveals that grass roots are very effective in reducing soil detachment rates. The equations obtained can be used to predict the effect of grass roots on soil erosion rates during concentrated runoff and to evaluate the ability of roots to increase topsoil resistance against erosion by concentrated flow. Calculations of relative erosion rates using the equations from the RUSLE and WEPP models indicate that the observed trend is better predicted with the RUSLE model and the WEPP model for croplands than with the WEPP model for rangelands.

Abstract: Extensive research exists on the effects of Canada thistle [Cirsium arvense (L.) Scop.] (CT) in annual cropland, but few studies have examined CT impacts on pasture and rangeland. While it is known that grazing impacts weed presence and abundance, little is understood about how specific grazing systems can be used as a prescriptive tool to alter weed populations, including CT. The purpose of this study was to experimentally test three cattle grazing systems, including (1) continuous or season-long grazing (SL), (2) short duration (SD) (or low intensity-high frequency) rotational grazing, and (3) high intensity-low frequency (HILF) rotational grazing, for their ability to reduce CT and release non-CT herbage within permanent pastures of central Alberta, Canada. A secondary objective was to evaluate season-long changes in the quality of CT shoots as potential forage throughout the growing season. Results showed that SL grazing maintained or increased severe CT infestations and reduced forage yield. In contrast, the HILF rotational system reduced CT shoot density and biomass, as well as flowering, and resulted in greater weed suppression than the SD system. Two intense defoliations annually over 2-3 years nearly eliminated CT stems. Remaining CT shoots were also primarily vegetative and greater in forage quality under HILF grazing. As a weed biological control tool for CT, prescribed grazing with an HILF system may be particularly important in areas where other control options, including the use of herbicides, are not possible due to environmental restrictions or inaccessibility to equipment.

Abstract: Summary Daily runoff depths from 28 plots (5 m � 2 m) recorded during a 2-year period in the semi-arid to subhumid highlands of Tigray were analyzed to study the effect of vegetation restoration in exclosures and to identify other factors influencing runoff production. Plots are distributed over three study sites and located in different land use types and on different combinations of soil type, vegetation cover and slope gradient. Runoff was found to be significantly reduced when a degraded area is allowed to rehabilitate after closure. Runoff depth is significantly correlated with event variables such as rain depth, rainfall intensity, storm duration and soil moisture content. Total vegetation cover is the most important plot variable explaining about 80% of the variation in runoff coefficients through an exponential decay function. Also the runoff generating rainfall threshold has a positive correlation with total vegetation cover. Runoff was found to be negligible when the vegetation cover exceeds 65%. Other important variables affecting runoff production in the study sites are soil organic matter, soil bulk density, litter cover and slope gradient.

Abstract: The dry and cold Tibetan Plateau is, by its nature, sensitive to desertification, and now human impacts and overexploitation makes things worse. One of the most important things involved in combating desertification is to stabilize mobile sandy land and facilitate revegetation. A study was conducted on shifting sand dunes of Tibetan Plateau to investigate the relationships among sand control, vegetation restoration and diversity dynamics of seed plant species. It was found that a positive correlation lay between sand stabilizing shrubs (Caragana korshinskii and Artemisia ordosica) and Leymus secalinus, a species of dominant and perennial grass in well-restored vegetation, but a negative correlation occurred between those shrubs and Agriophyllum arenarium indicator of shifting dunes. Secondly, sand stabilization facilitated revegetation, and total cover and cover of L. secalinus rose continuously from the beginning of restoration, but diversity indices showed a complex tendency. Based on these results, it was reasoned that on alpine shifting dunes of desertified regions, continual sand drifting caused by gales was the limiting factor for plant to survival. If sand barriers were established, sand drifting would be effectively controlled, then many native plant species could colonize shifting dunes gradually, so the process of revegetation was facilitated.

Abstract:

Abstract: Water erosion creates negative impacts on agricultural production, infrastructure, and water quality across the world. Regional-scale water erosion assessment is important, but limited by data availability and quality. Satellite remote sensing can contribute through providing spatial data to such assessments. During the past 30 years many studies have been published that did this to a greater or lesser extent. The objective of this paper is to review methodologies applied for water erosion assessment using satellite remote sensing. First, studies on erosion detection are treated. This comprises the detection of erosion features and eroded areas, as well as the assessment of off-site impacts such as sediment deposition and water quality of inland lakes. Second, the assessment of erosion controlling factors is evaluated. Four types of factors are discussed: topography, soil properties, vegetation cover, and management practices. Then, erosion mapping techniques are described that integrate products derived from satellite remote sensing with additional data sources. These techniques include erosion models and qualitative methods. Finally, validation methods used to assess the accuracy of maps produced with satellite data are discussed. It is concluded that a general lack of validation data is a main concern. Validation is of utmost importance to achieve regional operational monitoring systems, and close collaboration between the remote sensing community and field-based erosion scientists is therefore required.

Abstract: Spotted knapweed (Centaurea maculosa Lam.) is an invasive plant that alters species composition and grazing value of rangelands in the northwestern United States. The spread of invasive plants may be reduced by using livestock as a biological control. We determined if mature ewes and their lambs (n = 34 ewe/lamb pairs) consume more spotted knapweed when ewes and/or lambs are conditioned to fresh-cut spotted knapweed. Ewe/lamb pairs were randomly assigned to one of four conditioning treatments: ewes and lambs not conditioned to spotted knapweed (N), conditioned ewes with non-conditioned lambs (E), non-conditioned ewes with conditioned lambs (L), or conditioned ewes and lambs (both--B). Then, ewes and lambs were observed together for 5 days (Trial 1); 11 days later, lambs were observed for 4 days without their mothers (Trial 2). During conditioning, intake by conditioned and non-conditioned ewes and lambs varied over time (as-fed basis, treatment by day interaction; ewes P = 0.03; lambs P = 0.05). Overall, non-conditioned lambs (N, E) consumed more than conditioned lambs (L, B; P = 0.02). In Trial 1, N ewes consumed similar amounts of spotted knapweed and bromegrass (Bromus inermis Leyss.) as the E, L, and B ewes (P = 0.67). E ewes spent more time eating spotted knapweed than L ewes (P = 0.001), and E ewe/lamb pairs consumed more spotted knapweed than L ewe/lamb pairs (P = 0.02). In Trial 2, N lambs consumed less spotted knapweed than E, L, and B lambs (P = 0.06). L lambs consumed more than E lambs (P = 0.007). Conditioning ewes, lambs, or ewes and lambs did not increase time spent eating spotted knapweed when both grazed together in a drylot, but conditioned lambs, without their mothers present, consumed more spotted knapweed 11 days later than non-conditioned lambs. Conditioning lambs only in a group setting with their peers may have the greatest potential to enhance consumption of spotted knapweed, because of social facilitation and the predilection for young animals to try novel feeds.

Abstract: The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in [`]two-layer systems'. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment. We present an alternative hypothesis explaining both tree-grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity. We conclude that field studies are more likely to contribute to a general understanding of tree-grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas.

Abstract: In the Tigray highlands of Northern Ethiopia, the establishment of exclosures (i.e., areas closed for grazing and agriculture) has become an important measure to combat land degradation and restore vegetative cover. Exclosures are commonly found on steep slopes and downslope from a sediment source area. In this study their sediment trapping capacity and controlling factors were investigated. Total sediment depth turned out to be related to vegetation cover, sediment source area and in some cases slope gradient. Thickness of recent, short-term (< 20 years) sediment deposits was strongly related to distance from the top edge of the closed area, slope gradient, vegetation cover and characteristics of the sediment source area. Mean sediment deposition rates ranged between 26 and 123 Mg ha- 1 yr- 1. Under influence of vegetation and sediment deposition dark soils rich in organic matter (Phaeozems) develop. In view of their high sediment trapping capacity, exclosures are highly valued as efficient soil conservation measures in the Tigray highlands.

Abstract: We use a simple ecological sustainability simulator (SESS) [Diaz-Solis, H., Kothmann, M.M., Hamilton, W.T., Grant, W.E., 2003. A simple ecological sustainability simulator (SESS) for stocking rate management on semi-arid grazinglands, 76, 655] for rangelands with mean annual precipitation of 500 mm to evaluate tendencies in range productivity and cattle production under four management options: (1) supplemental feeding, (2) short-term reduction of stocking rate, (3) early weaning, and (4) adjustment of breeding seasons. We have made five modifications to SESS for the present paper. (1) Cattle mortality now occurs each month as a function of body condition. (2) Cows that are not pregnant 2 months after the end of the breeding season are sold. (3) Forage intake is calculated separately for each cohort of cows. (4) Cows that have been sold or have died are replaced just before the beginning of each breeding season (except for the short-term reduction of stocking rate strategy). (5) The calculation of stocking rate now includes cows, bulls, nursing calves, weaned heifers less than 20 months of age, and pre-reproductive heifers aged 20 months or older. Simulation results suggest the four management options might be ranked from best to worst, in terms of increasing cattle production while maintaining range productivity, as: (1) short-term reduction of stocking rate, (2) adjustment of breeding seasons, (3) early weaning, and (4) supplementation. Short-term reduction of high stocking rates reduces the deterioration of range productivity because of the reduction in the number of stock. Adjustment of breeding seasons such that periods of highest energy requirements of cows and calves coincide with periods of highest forage production increases percentage pregnancy. Early weaning of calves improves the body condition of cows and increases annual production of weaned calves, but does not reduce the stocking rate and thus does not improve range productivity. Supplemental feeding, and other management practices that artificially sustain herbivores, break the negative feedback that promotes good range productivity and maintains long-term system stability. In general, strategies to increase cattle production in semi-arid rangelands should be based on the improvement of natural forage production.

Abstract: Natural areas are becoming increasingly fragmented and embedded in an urban matrix. Natural and semi-natural areas at the urban/wildland interface are threatened by a variety of [�]edge effects 039;, and are especially vulnerable to invasion by introduced plants, with suburban gardens acting as significant sources of alien propagules. Urban/wildland interfaces also provide access for humans, leading to various types of disturbance. Alien plant invasions are one of the biggest threats facing remaining natural areas on the Cape Peninsula, South Africa. The area provides an ideal opportunity to study the dynamics of invasions at the urban/wildland interface, since the largest natural area, the Table Mountain National Park (TMNP), is surrounded by the city of Cape Town. We explored invasion patterns in Newlands Forest (a small section of the TMNP) and detailed the roles of habitat features and distance from putative source populations in three main habitat types: natural Afromontane forest, riverine woodland habitats, and plantations of exotic pines (Pinus radiata and P. pinaster). We also examined the role of disturbance in driving invasions in two of these habitat types (Afromontane forest and pine plantations). We hypothesized that alien richness and alien stem density would decrease with distance from the urban/wildland interface, and that alien richness and alien stem density would increase with increasing levels of human disturbance. Distance from putative source populations and levels of anthropogenic disturbance influenced alien richness in Newlands Forest but not alien stem density. Alien richness decreased significantly with distance from presumed sources in the pine habitat, and increased significantly with disturbance in the forest habitat. Percentage overstorey cover and soil pH were important environmental variables associated with alien plant species. A socio-economic approach is discussed as being the most effective approach to the management and prevention of alien plant species in Newlands Forest.

Abstract: The paper provides new and comparative insight into the ecological history of the two largest continental tropical forest areas during the Last Glacial Maximum (LGM). The tropical forest regions are of particular interest because they present a large source of heat and have been shown to have significant impact on the extra tropical atmospheric circulation. They are also the most intense land-based convective centers. Thus, especially from the tropics paleoecological information is needed as benchmarks for climate modeling. The African data for LGM climates were published earlier including the reconstructed paleoprecipitation patterns deduced from SSTs. The tropical South American LGM data were interpreted from pollen, geochemical, and [delta]18O (stable oxygen isotope) data from Brazil and selected surrounding areas. The available terrestrial data are consistent with the SST derived precipitation data for the tropical forests in Brazil and for Africa. However, the impact of LGM climate extremes was less severe in the Amazon than in the Congo basin. The LGM humid forest area (including evergreen and semi-deciduous forest types) in Africa was probably reduced by 84%. In contrast, the Amazon humid forest area probably shrank to 54% of their present-day extension. Still, there are different interpretations with respect to the amount of reduction of the Amazon forest area during the LGM. Although direct information about LGM climates in Amazonia is still limited the more detailed map obtained in the present work, however, allows a more reliable characterization of the last glacial tropical environment than previously published for the Amazon region.

Abstract: Summary Ecological restoration is still perceived by many conservationists, and the majority of economists, as a diversion, a delusion, and - far worse - a waste of money. In this paper we point out that restoration is in fact complementary not only to nature conservation but also to sustainable, equitable socio-economic development. This is because restoring and augmenting the natural capital base generates jobs and improves livelihoods and the quality of life of all in the economy. In developing countries, where most biodiversity hotspots occur, both conservation of nature and the restoration of degraded ecosystems will find local support only if they are clearly linked to socio-economic development. Conversely, sound socio-economic development in the environmentally damaged portions of those countries undoubtedly will require ecological restoration of the natural capital base. Nature conservation, ecological restoration, and sustainable economic development policies should therefore be planned, budgeted and executed conjointly.

Abstract: To identify the functioning of the soil-landscape system and its effects on plant growth for native rangeland the relationships between soil properties and landscape function analysis (LFA) indices and between plant growth characteristics and LFA indices were investigated. The results interpreted based on statistical analysis and expert knowledge. This research was carried out for a semi-arid rangeland in the Lar aquifer in Iran. Land stratification allowed the study area to be subdivided into Land Units, according to specified criteria including landform attributes (slope, aspect, and altitude), and vegetation type. A factorial model on the basis of a completely randomized design was used to analyse the data collected from 236 land units. The landscape function indices including nutrient cycling index, infiltration index, stability index, and landscape organization index were derived by various integrations of soil surface attributes. Landscape attributes differed from one another in their effects on the different landscape function indices. Increasing slope gradient significantly reduced all landscape function indices as well as soil organic carbon and total nitrogen percentages. Slope class exhibited highly significant interaction effects with vegetation type factors for stability, nutrient cycling, and landscape organization indices. Aspect did not significantly affect stability, infiltration, and landscape organization indices, but significantly affected the nutrient cycling index. The Duncan test indicated that north aspect (shady side) had the highest mean value (28.42) and south aspect the lowest mean value (25.57) for nutrient cycling index. These results are consistent with the effects of aspect on total soil nitrogen and soil organic carbon percentage for which the north aspect had the highest values. The values declined in the sequence east, west, and south aspects, respectively. This research indicates that the nature of native rangeland plant communities and their measures of production are closely related to nutrient cycling index.

Abstract: The forage quality of black locust (Robinia pseudoacacia L.), honey locust (Gleditsia triacanthos L.), bastard indigo (Amorpha fruticosa L.) and white mulberry (Morus alba L.), as well as of the associated herbaceous vegetation, was studied in a silvopastoral system. The study was conducted in a semi-arid grassland with poor sandy soil in northern Greece. Short-duration grazing (28 160;sheep/ha for 7 days) was repeated twice during the summer period (early July and late August) of 1992, 1993 and 1994. Crude protein content of foliage was maintained at relatively higher levels when plants were grazed compared to control, while neutral and acid detergent fibre content decreased significantly. Crude protein content of black locust and bastard indigo foliage was significantly higher compared to that of honey locust and white mulberry. However, white mulberry presented the highest in vitro digestibility among the four species tested. There was a tendency towards increased in vitro digestibility of the grazed plants 039; foliage, compared to that of the control (56% and 53.1%, respectively). In addition, short-duration summer grazing resulted in a small increase in the nutritive value and the in vitro digestibility of the associated herbaceous vegetation.

Abstract: Summary In this paper, we draw upon models from ecology and New Institutional Economics to examine the various mechanisms through which globalization can lead to loss in resilience of ecosystems and thus increase the vulnerability of poor people who depend on it. To illustrate ecological dynamics, we examine a semi-arid savanna ecosystem that is characterized by nonlinearities and multiple steady states. We discuss how traditional knowledge and institutions affect resource use patterns and resilience of such an ecosystem in the absence of trade. Then we examine the effects of trade liberalization and international technology transfers on institutional and ecological dynamics, and consequently, on poverty.

Abstract: Ceropegia macmasteri, a new species from Cathcart in the Eastern Cape Province of South Africa, is only known from a single population in Dohne sourveld grassland where it occurs with another rare local endemic species of the Ceropegieae, Brachystelma cathcartense R.A.Dyer. The new species, an herbaceous grassland plant with a tuberous rootstock, most closely resembles C. stentiae E.A.Bruce, but is distinguished by its linear-erect corona lobes and inner corona conniving to form a central column.

Abstract: The multiple benefits from livestock production to rural households are evaluated in Thorndale, a communal area of the Limpopo Province South Africa. Monetary values of livestock products are presented. Values from most previous studies are static (and thus outdated), as a result of conceptual and methodological shifts. The net monetary value of the direct benefits from livestock was estimated as $656 per household/annum, excluding the holding of cattle for savings. The net value is equivalent to 22.7% of the value of the other livelihood sources that were considered, and inclusive of cash income streams, crops, and secondary woodland resources. A net 168% herd increase in livestock was recorded between 1993 and 1999. More households owned goats compared to cattle, and cattle were important for use as draught power, and for milk. Households without livestock benefited through gifts and services, valued at $33 per household/annum. Policy concerns are the provision of adequate market and pricing mechanisms for communal area livestock, tailored savings, investment support, credit schemes, and infrastructure. An appropriate multipurpose benefit production model, other than a commercialised model is suggested for the sector.

Abstract: The distribution of pollen in marine sediments is used to record vegetation change on the continent. Generally, a good latitudinal correspondence exists between the distribution patterns of pollen in the marine surface sediments and the occurrence of the source plants on the adjacent continent. To investigate land-sea interactions during deglaciation, we compare proxies for continental (pollen assemblages) and marine conditions (alkenone-derived sea surface temperatures) of two high-resolution, radiocarbon-dated sedimentary records from the tropical southeast Atlantic. The southern site is located West of the Cunene River mouth; the northern site is located West of the Angolan Huambe Mountains. It is inferred that the vegetation in Angola developed from Afroalpine and open savannah during the last Glacial maximum (LGM) via Afromontane Podocarpus forest during Heinrich Event 1 (H1), to an early increase of lowland forest after 14.5 ka. The vegetation record indicates dry and cold conditions during the LGM, cool and wet conditions during H1 and a gradual rise in temperature starting well before the Younger Dryas (YD) period. Terrestrial and oceanic climate developments seem largely running parallel, in contrast to the situation ca. 5° further South, where marine and terrestrial developments diverge during the YD. The cool and wet conditions in tropical West Africa, South of the equator, during H1 suggest that low-latitude insolation variation is more important than the slowdown of the thermohaline circulation for the climate in tropical Africa.

Abstract: Tillage, organic resources and fertiliser effects on soil carbon (C) dynamics were investigated in 2000 and 2001 in Burkina Faso (West Africa). A split plot design with four replications was laid-out on a loamy-sand Ferric Lixisol with till and no-till as main treatments and fertiliser types as sub-treatments. Soil was fractionated physically into coarse (0.250-2 mm), medium (0.053-0.250 mm) and fine fractions (< 0.053 mm). Particulate organic carbon (POC) accounted for 47-53% of total soil organic carbon (SOC) concentration and particulate organic nitrogen (PON) for 30-37% of total soil nitrogen concentration. The POC decreased from 53% of total SOC in 2000 to 47% of total SOC in 2001. Tillage increased the contribution of POC to SOC. No-till led to the lowest loss in SOC in the fine fraction compared to tilled plots. Well-decomposed compost and single urea application in tilled as well as in no-till plots induced loss in POC. Crop N uptake was enhanced in tilled plots and may be up to 226 kg N ha-1 against a maximum of 146 kg N ha-1 in no-till plots. Combining crop residues and urea enhanced incorporation of new organic matter in the coarse fraction and the reduction of soil carbon mineralisation from the fine fraction. The PON and crop N uptake are strongly correlated in both till and no-till plots. Mineral-associated N is more correlated to N uptake by crop in tilled than in no-till plots. Combining recalcitrant organic resources and nitrogen fertiliser is the best option for sustaining crop production and reducing soil carbon decline in the more stabilised soil fraction in the semi-arid West Africa.

Abstract: Three rates of stocking (low: one sheep 2.25 ha-1 year-1, medium: one sheep 1.5 ha-1 year-1 and high: one sheep 0.75 ha-1 year-1) were studied for seven seasons (1990/91-1996/97) on native unimproved range and on range over-sown with fodder shrubs at Maragha, northwest Syria. There were eight Awassi sheep in each stocking rate treatment, and the treatments were replicated three times in fenced paddocks. Milk yield, lamb production, liveweight and supplementary feeding of the sheep were monitored. The results showed significantly higher forage availability on the range over-sown with fodder shrubs, exceeding the native pasture by 82% and 41% in the medium and high rainfall seasons, respectively, and by 142% and 379% in the average and low rainfall seasons. The total energy used in the supplementary feed was greater under the native pasture than that in the shrub-sown pasture in five out of the seven seasons, while crude protein consumption was greater in the native pasture than on the shrub-sown pasture in all seven seasons. Milk production and lamb body mass were higher on shrub-sown pasture than those in native pasture in four and six out of the seven seasons, respectively. Benefits obtained from reduced feed costs, extra milk and lamb sales were higher on shrub-sown pasture than those in the native pasture in five out of the seven seasons. Total benefits measured over the entire study period were highest under the high stocking rate, reaching about 77 US$ ha-1. We concluded that shrub plantations in west Asia could safely be utilized at stocking rate of one sheep 0.75 ha-1 year-1 for the benefits of the pasture and users.

Abstract: A vegetation survey of natural grasslands was undertaken in the urban areas of Gauteng, supporting about 20% of the country's population. Relevés were compiled in 132 sample plots placed in selected open spaces in the study area. A floristic-sociological classification revealed eight grassland communities, represented by 59 relevés. A hierarchical classification, description and ecological interpretation of these plant communities are presented.

Abstract: Models to support decisions on rangeland policy must address the close links between ecological, economic, and social processes, and the adaptation of participants through time. We used an agent-based modeling approach to implement a parsimonious conceptual model of rangelands that included biophysical processes central to the functioning of rangelands, commercial enterprises, and institutions. The model operated on a monthly time step, and used economic and biophysical conditions to stimulate changes in management policies and learning. Our simple model reproduced the general patterns of forage growth and livestock dynamics in north-east Australia, and results illustrate consequences of interactions between environmental heterogeneity and learning rate.

Abstract: This paper presents an environmental exposure assessment model for estimating chronic intake of vanadium (a transition metal) by cattle farmed extensively in areas contaminated by vanadium pollutants. The exposure model differs from most other models in several ways: (1) it does not rely heavily on extrapolating information from the point source (e.g. stack height, exit velocity, exit diameter) to the point of exposure. (2) It incorporates the physiological constraints of the species exposed. (3) It takes into account oral as well as inhalation exposure. (4) It addresses terrain, by using measurements at the point of exposure. (5) It accounts for existing background concentrations of pollutants and pollutants from multiple sources. (6) It uses a stochastic process with distribution functions to account for variability in the data over time. Environmental inputs into the model included aerial fall-out sample vanadium (n = 566), unwashed grass sample vanadium (n = 342) and soluble soil sample vanadium (n = 342). Physiological cattle inputs were derived from two cohorts of Brahman-cross sentinel cattle (n = 30). The model provided an estimate of the chronic external exposure dose of vanadium for two separate groups of cattle grazing over a 5-year period (1999-2004) immediately adjacent (median dose = 2.14 mg vanadium/kg body weight/day) and 2 km away (median dose = 1.07 mg/kg/day) from a South African vanadium-processing plant, respectively. The final output of the model is a distribution curve of the probable vanadium intake based on the variability within the inputs over the 5-year period of the study. The model is adaptable enough for application to other transition metals and species (including man), and could be used as an alternative to plume-dispersion modelling.

Abstract: Turkey has been one of the major sheep and goat producers of Europe and the West Asia and North Africa (WANA) region in the 20th century. Sheep and goats followed a declining trend since the early 1980s and are no longer the major meat and milk supplying species. Many factors have contributed to this situation among which are the high population growth rate, low genetic potential of the indigenous breeds, inappropriate breeding strategies, decrease in the area covered by pastures and rangelands, intensification of agriculture and livestock production, better education and demand for high status jobs, support regimes favouring poultry and dairy production, unfavourable market conditions for sheep and goat production. Small ruminant production is extensively and traditionally practiced and is characterised by low inputs and low outputs. In addition, sheep and goat farmers generally are reluctant to adopt novel husbandry methods to improve their income. Under these conditions, the declining trend is going to continue. Unfortunately, no serious efforts are made by the state authorities to introduce support for sheep and goat production under liberal market conditions.

Abstract: Summary * 1Fire is important for the maintenance and conservation of African savanna ecosystems. Despite the importance of fire intensity as a key element of the fire regime, it is seldom measured or included in fire records. * 2We estimated fire intensity in the Kruger National Park, South Africa, by documenting fuel loads, fuel moisture contents, rates of fire spread and the heat yields of fuel in 956 experimental plot burns over 21 years. * 3Individual fires were conducted in five different months (February, April, August, October and December) and at five different return intervals (1, 2, 3, 4 and 6 years). Estimated fire intensities ranged from 28 to 17 905 kW m�1. Fire season had a significant effect on fire intensity. Mean fire intensities were lowest in summer fires (1225 kW m�1), increased in autumn fires (1724 kW m�1) and highest in winter fires (2314 kW m�1); they were associated with a threefold difference between the mean moisture content of grass fuels in winter (28%) and summer (88%). * 4Mean fuel loads increased with post-fire age, from 2964 kg ha�1 on annually burnt plots to 3972 kg ha�1 on biennial, triennial and quadrennial burnt plots (which did not differ significantly), but decreased to 2881 kg ha�1 on sexennial burnt plots. Fuel loads also increased with increasing rainfall over the previous 2 years. * 5Mean fire intensities showed no significant differences between annual burns and burns in the biennial, triennial and quadrennial categories, despite lower fuel loads in annual burns, suggesting that seasonal fuel moisture effects overrode those of fuel load. Mean fire intensity in sexennial burns was less than half that of other burns (638 vs. 1969 kW m�1). * 6We used relationships between season of fire, fuel loads and fire intensity in conjunction with the park's fire records to reconstruct broad fire intensity regimes. Changes in management from regular prescribed burning to �natural� fires over the past four decades have resulted in a decrease in moderate-intensity fires and an increase in high-intensity fires. * 7The highest fire intensities measured in our study (11 000 � > 17 500 kW m�1) were significantly higher than those previously reported for African savannas, but were similar to those in South American cerrado vegetation. The mean fire intensity for late dry season (winter) fires in our study was less than half that reported for late dry season fires in savannas in northern Australia. * 8Synthesis and applications. Fire intensity has important effects on savanna vegetation, especially on the dynamics of the tree layer. Fire intensity varies with season (because of differences in fuel moisture) as well as with fuel load. Managers of African savannas can manipulate fire intensity by choosing the season of fire, and further by burning in years with higher or lower fuel loads. The basic relationships described here can also be used to enhance fire records, with a view to building a long-term data set for the ongoing assessment of the effectiveness of fire management.

Abstract: Cyperus articulatus L. and Cyperus corymbosus Rottb. were studied in southern Africa and were found to be synonymous. The latter bears laminae, has longer bracts and frequently has less septate culms than the former but these differences are phenotypic. Phenotypes formerly referred to C. corymbosus are generally rare and scattered, occupying the drier fringing zones of populations. A map of the distributional range of C. articulatus in southern Africa is provided, along with an illustration of the [`]corymbosus' phenotype.

Abstract: Early warning systems (EWS) tend to focus on the identification of slow onset disasters such famine and epidemic disease. Since hazardous environmental conditions often precede disastrous outcomes by many months, effective monitoring via satellite and in situ observations can successfully guide mitigation activities. Accurate short term forecasts of NDVI could increase lead times, making early warning earlier. This paper presents a simple empirical model for making 1 to 4 month NDVI projections. These statistical projections are based on parameterized satellite rainfall estimates (RFE) and relative humidity demand (RHD). A quasi-global, 1 month ahead, 1° study demonstrates reasonable accuracies in many semi-arid regions. In Africa, a 0.1° cross-validated skill assessment quantifies the technique's applicability at 1 to 4 month forecast intervals. These results suggest that useful projections can be made over many semi-arid, food insecure regions of Africa, with plausible extensions to drought prone areas of Asia, Australia and South America.

Abstract: Camel grazing is recognized as a primary cause of ecological degradation in the UAE. A study of perennial plant species <1 m in height was conducted along a fence separating continuously camel grazed land from land in which camels had been replaced by oryx and gazelle species for 5 years (Al Maha). Vegetation regeneration in Al Maha in the absence of camels was considerable on all substrates (gravel, stable sand, and semi-stable sand) but was greatest on the gravel substratum, indicating that ecology in this habitat is most at risk. Observed regeneration was primarily through vegetative reproduction and growth of existing plants, showing that existing species can tolerate heavy grazing. Therefore, an equilibrium grazing model of continuous and reversible vegetation dynamics is most suitable for management of this ecological zone. Species richness was greater in Al Maha due to the greater number of plants, but biodiversity was unaffected. There was some evidence of localized dune stabilization within Al Maha due to increased vegetative cover. Further recovery of vegetation within Al Maha is discussed. This study highlights the need for reduced grazing pressure throughout the Dubai inland desert, and in particular on gravel substrata.

Abstract: Marine pollution is a major threat to human and environmental health. Given the complexity of function of marine and coastal ecosystems, it is unlikely that a balanced view of the nature and extent of risk will easily be achieved if human and environmental risk assessments continue to be conducted in isolation. Here, the integration of assessment protocols is advocated as a holistic means of improving risk management. Biomarkers can provide the common conceptual framework and measurable endpoints necessary for successful integration. Examples are given of the ways in which suites of biomarkers encompassing molecular change, cellular pathology and physiological impairment can be developed and adapted for human and ecological scenarios. By placing a greater emphasis on the health status of impacted biota, it is more likely that risk assessment will develop the efficiency, reliability and predictive power to adapt to the unforeseen environmental threats that are an inevitable consequence of human development and global change.

Abstract: Two experiments were conducted to investigate the effects of PEG and feed blocks on digestion of shrub species consumed by goats (experiment 1) and kid growth while browsing during the dry season (experiment 2). In experiment 1, in vitro gas production was determined using a rumen fermenter. Six shrub species were incubated separately (Erica arborea, Phillyrea angustifolia, Pistacia lentiscus, Myrtus communis, Quercus suber, and Viburnum tinus). Effects of polyethylene glycol (PEG 4000) and feed block supply were investigated. In experiment 2, 21 local kids, 18.75 (±1.4) kg body weight (BW) were allowed to browse in shrub-lands and allocated to three treatments in a production trial lasting 147 days (July-December). Control group receive no supplement, whereas the two other groups received either PEG-free (B) or PEG-containing feed blocks (B-PEG). All shrubs were low in crude protein (59-91 g kg-1 dry matter) but high in total condensed tannins; mean content was 43 g kg-1 DM (8.8-65) for bound condensed tannin and 205 g kg-1 DM (10.8-363) for free condensed tannin. Gas volume produced after 24 h differed among shrub species (P<0.05). V. tinus produced the highest volume (77.8 ml g-1 organic matter) and Q. suber the lowest (35 ml g-1 OM). The mean rate of fermentation was 0.135 h-1 (0.121-0.150 h-1). PEG addition increased gas production by 48.5%, volatile fatty acid by 38.4% and organic matter fermented by 41.7% of the mixture of shrubs (P<0.05). In the practical trial, the use of blocks with and without PEG avoided BW loss of the goats under dry season. While the control group lost 19 g day-1, the bloc supplemented groups grew at 12 g day-1 (-PEG) and 24 (+PEG) g day-1.

Abstract: In this study we employ the TRIFFID (Top-down Representation of Interactive Flora and Foliage Including Dynamics) Dynamic Global Vegetation Model (DGVM) and the Hadley Centre Atmospheric General Circulation Model version 3 (HadAM3 GCM) to investigate vegetation distributions and climate-vegetation feedbacks during the Mid-Pliocene, and examine the implications of these results for the origins of hominid bipedalism. The TRIFFID model outputs support extant palaeoenvironmental reconstructions for the Mid-Pliocene provided by the PRISM Group (Pliocene Research Interpretations and Synoptic Mapping). Compared to the pre-industrial, TRIFFID simulates a significant increase in forest cover during the Mid-Pliocene, composed of needle leaf trees in the higher latitudes of the Northern Hemisphere and broad leaf trees in other regions. Needle leaf trees extend from the Arctic Coast into the northern mid latitudes. The fractional coverage of bare soil declines in North Africa, the Arabian Peninsula, Australia and southern South America, a pattern that is consistent with PRISM's assertion of less extensive arid deserts. A significant increase in the fractional coverage of both broad leaf trees in Africa and South America in the Mid-Pliocene scenario is not indicative of a major expansion of tropical rainforests. Rather, it represents an expansion of general woodland type habitats. The principal impact of using a DGVM on the GCM predicted climatology for the Mid-Pliocene is to reduce minimum and maximum temperature extremes, thus reducing the seasonality of temperature over wide regions. The predicted Pliocene expansion in broad leaf trees in Africa is difficult to reconcile with the [`]savannah hypothesis' for the evolution of hominid bipedalism. Rather the results lend credence to an alternative hypothesis which suggests that bipedalism evolved in wooded to forested ecosystems and was, for several million years, linked to arborealism.

Abstract: Susan Kent had been working on a project excavating an open-air archaeological site in the eastern Free State, South Africa, at the time of her death. She had commissioned geological studies, which had indicated that the archaeological horizon was in situ, and had involved colleagues in taking dating, pollen, and phytolith samples. We decided to continue with the analysis of the samples after her death and to complete the analysis of the artifacts from the site. This multifaceted approach to understanding the context of the archaeological horizon was the background against which Susan intended to investigate the spatial distribution of the lithic material as a means of identifying activity areas at the site. This chapter reports some of the results of the continuing analysis. The archaeological horizon has been dated to around 30 ka by optically stimulated luminescence. This date supports the final Middle Stone Age or Transitional Middle Stone Age/Later Stone Age designation suggested by a preliminary analysis of part of the lithic sample. Paleoenvironmental information from the site indicates that conditions were favorable for human settlement in the eastern Free State area during this period. Although the site may not necessarily be suitable to answer all the questions Susan initially asked of it, it will certainly make a contribution to our understanding of human settlement of the area during this little-researched time period of the central interior.

Abstract: Alluvial and braided fluvial deposits of the 3.2 Ga Moodies Group in the Barberton greenstone belt, South Africa, are analyzed petrographically and geochemically to identify their source rocks (provenance) and assess the degree and type(s) of weathering required to produce the observed Moodies sediment compositions. Conglomerate, sandstone, and shale data give somewhat differing pictures of provenance and weathering due to derivation from different components within the source terrane and size and compositional fractionation during transport. The results suggest that shale geochemistry provides the most accurate estimate provenance, although both rare-earth element and trace element (Th, Sc, Zr, Cr, and Ti) data must be used in combination to give the best results. The source area for Moodies Group sediments was dominated by tonalite, felsic volcanic rock, komatiite-basalt, and granite. Based on mineralogical and major-element divergence from estimated source area composition, the Moodies Group sediments are remnants of an aggressive weathering environment. Labile materials, such as komatiite, basalt, and coarse plagioclase grains, decomposed almost entirely to clays and solutes, and the chemical index of alteration for Moodies shale is well above the global average. An aggressive weathering environment in the Archean may have been achieved by increased rainfall, higher temperatures, and/or higher atmospheric PCO2. More likely, a combination of these conditions worked to offset the inhibitory weathering effects of a plant-free environment.

Abstract: In this study, we sought to address the issue of how to derive an extended synthetic record of fire incidence and timing at regional scale that would be representative of a short remotely-sensed calibration record. We used annual rainfall and simulated annual ground stratum growth to develop multiple regression relationships for prediction of annual fire probability and proportion of late (August-November) fires from AVHRR NDVI fire footprint data across Australian tropical savannas. Relationships were examined using spatial averaging in moving windows varying from 3 � 3 to 61 � 61 pixels in size. Model fits as measured by R2 improved as window size increased, but output layers became smoother and less representative of natural heterogeneity. A 25 � 25 pixel window was selected as the best compromise between model fit and smoothing. A 113-year synthetic record of annual fire probability and proportion of late fires was generated using the spatially explicit layers of model coefficients. The statistical properties of the synthetic fire probabilities were compared with those derived from the available fire footprint record, using a simple vegetation classification based on ground stratum type for spatial stratification. The two data sets showed a strong correspondence for both burned area and fire probability; spatial variation in mean and coefficient of variation of fire probability was representative of that observed in the historical record. There was significant temporal variation in the synthetic annual fire probability for different vegetation zones across the tropical savanna region for the full 113-year length of record. This simple approach could readily be applied to other areas of the world provided rainfall data are available and annual ground stratum growth can be simulated with a suitable model or estimated with remote sensing.

Abstract: This paper uses a scenario analysis system - Range-ASSESS - to examine the potential for gains and losses of soil carbon in the Australian rangelands as affected by grazing and climate. The analysis involves a factorial examination of the effect of stocking rates and all possible 5-year historical climates between 1889 and 1999. The analysis also looks at the sensitivity of results to the method of calculation of safe carrying capacity, and to the thresholds used to calculate grazing and dryness indices that drive transitions in state and transition models. The analysis showed that different vegetation zones produced different responses to changes in stocking depending upon the spatial distribution of dryness index, nature of carbon state and transition model, rules governing transitions, and relative significance of soil carbon. At a stocking density equivalent to 100% of 1997 levels, the soil carbon loss from rangelands was about 400 Mt C in 40% of the 5-year periods using a sensitive growth deviation threshold to determine dryness index. If a less sensitive threshold was used, potential loss was reduced to about 200 Mt C. If the grazing pressure threshold for a grazing index of four is adjusted to a more generous level, then potential losses in the dry periods are substantially reduced. The analysis is intended to be indicative of a likely approximate outcome rather than a quantitative measure of system response. The results indicate that the interpretation of the effect of the drought-grazing pressure interaction on perennial plant survival, and consequent organic carbon input to soils, is a major source of uncertainty and a critical area for more experimental measurement.

Abstract: The leaf area index (LAI) product from the Moderate Resolution Imaging Spectroradiometer (MODIS) is important for monitoring and modelling global change and terrestrial dynamics at many scales. The algorithm relies on spectral reflectances and a six biome land cover classification. Evaluation of the specific behaviour and performance of the product for regions of the globe such as Australia are needed to assist with product refinement and validation. We made an assessment of Collection 4 of the MODIS LAI product using four approaches: (a) assessment against a continental scale Structural Classification of Australian Vegetation (SCAV); (b) assessment against a continental scale land use classification (LUC); (c) assessment against historical field-based measurement of LAI collected prior to the Terra Mission; and (d) direct comparison of MODIS LAI with coincident field measurements of LAI, mostly from hemispherical photography. The MODIS LAI product produced a wide variety of geographically and structurally specific temporal response profiles between different classes and even for sub-groups within classes of the SCAV. Historical and concurrent field measurements indicated that MODIS LAI was giving reasonable estimates for LAI for most cover types and land use types, but that major overestimation of LAI occurs in some eastern Australian open forests and woodlands. The six biome structural land cover classification showed some significant deviations in class allocation compared to the SCAV particularly where grasslands are allocated to shrubland, savanna woodlands are allocated to shrubland, savanna and broadleaf forest, and open forests are allocated to savanna and broadleaf forest. The land cover and LAI products could benefit from some additional examination of Australian data addressing the structural representation of Eucalypt canopies in the "space of canopy realisation" for savanna and broadleaf forest classes.

Abstract: Summary Restoration of ecological processes is key to restoring the capacity of ecosystems to support social, economic, cultural and aesthetic values. The sustainability of the restored system also depends on processes associated with carbon, nutrient and hydrologic cycles, yet most restoration monitoring is limited to plant community composition. Our research has shown that short-term plant composition monitoring is a necessary but insufficient predictor of long-term restoration success. Long-term (up to 75 years) studies in the western United States show that short-term monitoring of plant community composition alone incorrectly predicted the failure of treatments that were ultimately successful, and the success of treatments that ultimately failed. We propose that vegetation composition monitoring be combined with one or more ecological process indicators reflecting changes in three fundamental ecosystem attributes on which restoration success depends: soil and site stability, hydrologic function and biotic integrity. These simple, rapid, plot-level indicators reflect changes in resource redistribution and vegetation structure. We include a case study involving restoration of mixed grass prairie on mineland in the west-central United States.

Abstract: Science is frequently touted as the solution to dryland management problems, yet most management decisions are, by necessity, based primarily on expert knowledge and experience. This paper describes an integrated framework for organizing, synthesizing, and applying our growing understanding of aridland ecosystems using a flexible, multi-objective assessment, monitoring, and management approach. The framework is dual-purpose: (1) to coordinate the use of existing tools, resources, and diffuse knowledge, and (2) to facilitate the integration and application of new knowledge as it is developed. In particular, this framework must facilitate the integration of new knowledge about linkages among landscape units across scales. The framework includes five elements: (1) an ecological site-based approach for categorizing land based on soils and climate, (2) a repository for organizing existing data and knowledge about each ecological site, (3) conceptual models that organize information on the impacts of management and climate variability, and protocols for (4) assessing and (5) monitoring key ecosystem attributes fundamental to a variety of management objectives. Within this framework, basic and applied research are explicitly linked to management of arid and semi-arid ecosystems to more effectively articulate research questions and set research priorities.

Abstract: In tropical West Africa, distribution patterns of forest islands in savannas are influenced by fires which occur regularly in the grass stratum. Along continuous forest&ndash;savanna transects in the Como&eacute; National Park, the change in the amount and composition of non-woody phytomass was investigated from savanna to forest interior. This was correlated with the cover of vegetation strata above, soil depth, and the occurrence of seasonal surface fires. Phytomass mainly consisted of leaf litter in the forests (about 400 g m&minus;2 at the end of the rainy season, and about 600 g m&minus;2 at the end of the dry season) and of grasses in the savanna (about 900 g m&minus;2). Low grass biomass appeared to be primarily the result of suppression by competing woody species and not of shallow soil. The occurrence of early dry-season fires seemed to be determined mainly by the amount of grass biomass as fuel because fires occurred in almost all savanna plots while forest sites remained unaffected. However, late dry-season fires will encounter higher amounts of leaf litter raising fire probability in forests. Due to the importance of the amount of combustible phytomass, fire probability and intensity might increase with annual precipitation in both savanna and forest.

Abstract: The greenhouse gas emissions from agricultural systems contribute significantly to the national budgets for most countries in Europe. Measurement techniques that can identify and quantify emissions are essential in order to improve the selection process of emission reduction options and to enable quantification of the effect of such options. Fast box emission measurements and mobile plume measurements were used to evaluate greenhouse gas emissions from farm sites. The box measurement technique was used to evaluate emissions from farmyard manure and several other potential source areas within the farm. Significant (up to 250 g CH4 m-2 day-1and 0.4 g N2O m-2 day-1) emissions from ditches close to stables on the farm site were found. Plume emission measurements from individual manure storages were performed at three sites. For a manure storage with 1200 m3 dairy slurry in Wageningen emission factors of 11 ± 5 g CH4 m-3 manure day-1 and 14 ± 8 mg N2O m-3 manure day-1 were obtained in February 2002. Mobile plume measurements were carried out during 4 days at distances between 30 and 300 m downwind of 20 different farms. Total farm emissions levels ranged from 14 to 95 kg CH4 day-1 for these sites. Expressed as emission per animal the levels were 0.7 ± 0.4 kg CH4 animal-1 day-1 for conventional farms. For three farms that used straw bedding for the animals1.4 ± 0.2 kg CH4 animal-1 day-1 was obtained. These factors include both respired methane and emission from manure in the stable and the outside storages. For a subset of these farms the CH4 emission was compared with monthly averaged model emission calculations using FarmGHG. This model calculates imports, exports and flows of all products through the internal chains on the farm using daily time steps. The fit of modelled versus measured data has a slope of 0.97 but r2 = 0.27. Measurements and model emission estimates agree well on average, for large farms within 30%. For small farms the differences can be up to a factor of 3. CH4 emissions during winter seem to be underestimated.

Abstract: We investigated palaeoclimatic change in the Turkana Basin during the Pliocene climatic shift toward increased aridity in Africa. We analyzed the palaeoecology of this area using mammal faunas as environmental indicators. Twenty Plio-Pleistocene fossil assemblages and a comparative dataset of 16 modern localities covering a wide range of climatic and ecological conditions across Africa were analyzed. We constructed community profiles using taxonomic variables which reflect ecological information. Principal component analysis and bivariate correlation were used to study changes in the community structure of these mammalian faunas and to draw palaeoenvironmental inferences. Subsequently, least-squares regressions yielded climatic estimates (annual rainfall and drought length) for the studied period. An additional set of 8 modern faunas was used to validate these regression models. The climatic estimates showed a drying trend throughout the sequence. The biomes in the Turkana Basin changed from semi-evergreen rain forest to deciduous woodland and savanna during the middle-late Pliocene. This was the most important climatic shift detected in our study. Evidence suggests a continuous presence of savannas from 2.5 million years ago onwards. This pattern of climatic change is consistent with isotopic evidence on global climate, and with independently derived regional palaeoenvironmental evidence (i.e., micromammals, palaeovegetation, soil carbonates and palaeosols).

Abstract: The modern environmental management literature stresses the need for community involvement to identify indicators to monitor progress towards sustainable development and environmental management goals. The purpose of this paper is to assess the impact of participatory processes on sustainability indicator identification and environmental management in three disparate case studies. The first is a process of developing partnerships between First Nations communities, environmental groups, and forestry companies to resolve conflicts over forest management in Western Canada. The second describes a situation in Botswana where local pastoral communities worked with development researchers to reduce desertification. The third case study details an on-going government led process of developing sustainability indicators in Guernsey, UK, that was designed to monitor the environmental, social, and economic impacts of changes in the economy. The comparative assessment between case studies allows us to draw three primary conclusions. (1) The identification and collection of sustainability indicators not only provide valuable databases for making management decisions, but the process of engaging people to select indicators also provides an opportunity for community empowerment that conventional development approaches have failed to provide. (2) Multi-stakeholder processes must formally feed into decision-making forums or they risk being viewed as irrelevant by policy-makers and stakeholders. (3) Since ecological boundaries rarely meet up with political jurisdictions, it is necessary to be flexible when choosing the scale at which monitoring and decision-making occurs. This requires an awareness of major environmental pathways that run through landscapes to understand how seemingly remote areas may be connected in ways that are not immediately apparent.

Abstract: Bufflelgrass (Pennisetum ciliare syn. Cenchrus ciliaris) is an African grass that has been widely introduced in subtropical arid regions of the world to improve rangelands for cattle production. However, it can have a negative effect on the diversity of native plant communities. Buffelgrass was introduced to Sonora, Mexico in the 1970s as a means to bolster the cattle industry. "Desmonte," the process by which native desert vegetation is removed in preparation for buffelgrass seeding, alters the land surface such that buffelgrass plots are easily detectable from aerial and Landsat satellite images. We estimated the extent of conversion to buffelgrass in a 1,850,000 ha area centered on Hermosillo, from MSS and TM images from 1973, 1983, 1990 and 2000. We then compared the relative above-ground productivity of buffelgrass to native vegetation using Normalized Difference Vegetation Index values (NDVI) from Landsat and Moderate Resolution Imaging Spectrometer (MODIS) satellite sensor systems. Buffelgrass pastures have increased from just 7700 ha in 1973 to over 140,000 ha in 2000. Buffelgrass pastures now cover 8% of the land surface in the study area. Buffelgrass pastures have lower net primary productivity, estimated by MODIS NDVI values, than unconverted desert land. The desmonte process removes trees and shrubs, while the buffelgrass plantings are often sparse, leading to an apparent net loss in net primary production from land conversion. We recommend that the desmonte process be discontinued until its efficacy and safety for native ecosystems can be established, and that a comprehensive plan for preserving biodiversity while accomodating economic development be established for this region of the Sonoran Desert in Mexico.

Abstract: Summary This study demonstrates that there is a relationship between socioeconomic problems in parts of West Africa and remote-sensing-derived environmental information about the region (normalized difference vegetation index (NDVI), net primary production (NPP), and gridded rainfall data). Further, it finds that using both remotely sensed data and site-specific information from participatory rural appraisal (PRA) reports enables an improved understanding of natural resource management problems in the region. The study uses 100 PRA reports as sources of data on socioeconomic and natural resource management problems in Senegal and The Gambia. Utilizing a binary variable to extract semi-quantitative information from the reports, the study examines 10 PRA tools for their usefulness.

Abstract: Renewable energy usage in Africa has been reviewed using South Africa, Egypt, Nigeria and Mali as case studies. The various national energy policies of these countries were analysed and areas that require attention to achieve sustainability were highlighted. On the overall, the success of sustainable development in Africa lies in addressing the imminent energy crisis in the continent. Excessive usage of fuel wood is already creating considerable environmental problems especially in the Sahel. Africa has all the potentials to solve its energy problems if appropriate infrastructural support can be provided for harnessing the abundant renewable resources in the continent, and if skills are pooled together and experiences shared in addressing the key issues.

Abstract: Grasslands were once widespread and species-rich ecosystems. They have drastically decreased throughout the world, largely due to changes in land-uses. Remnant grasslands are often highly degraded and disconnected and require active conservation. In order for grasslands to be maintained worldwide, protected areas need to be created. While adequately creating and managing protected areas has proven difficult, this can be improved by following a three-point guideline: (1) consider many ecological groups (birds, insects, plants); (2) use conservation biology knowledge; (3) seek agreements with concerned parties by comprehending elements of economy, politics and sociology. Based on the example of La Crau, a steppe area in South-eastern France, this review aims at (i) illustrating that this guideline can facilitate creating and managing protected areas and (ii) proposing improvement to the guideline while keeping it simple. In La Crau, the need for conservation was first acknowledged in 1975. Between 1983, when a request for a protection decree was made and 1990, when the first concrete protection measure was taken, 20% of the steppe disappeared. It took another 8 years to reach a concerted management plan in 1998. The review shows how using ecological guidelines would have helped better and faster protection of the steppe. Improvements to the guideline drawn from the La Crau experience include: the protection of some traditional practices; the protection of some degraded habitats that can substitute for habitats that no longer exist; the restoration of degraded habitats that do not qualify for protection; and the flexibility of the management plan.

Abstract: Biodiversity in Africa, Madagascar and smaller surrounding islands is both globally extraordinary and increasingly threatened. However, to date no analyses have effectively integrated species values (e.g., richness, endemism) [`]non-species' values (e.g., migrations, intact assemblages), and threats into a single assessment of conservation priorities. We present such an analysis for the 119 ecoregions of Africa, Madagascar and smaller islands. Biodiversity is not evenly distributed across Africa and patterns vary somewhat among taxonomic groups. Analyses of most vertebrates (i.e., birds, mammals, amphibians) tend to identify one set of priority ecoregions, while plants, reptiles, and invertebrates highlight additional areas. [`]Non-species' biological values are not correlated with species measures and thus indicate another set of ecoregions. Combining species and non-species values is therefore crucial for assembling a comprehensive portfolio of conservation priorities across Africa. Threats to biodiversity are also unevenly distributed across Africa. We calculate a synthetic threat index using remaining habitat, habitat block size, degree of habitat fragmentation, coverage within protected areas, human population density, and the extinction risk of species. This threat index is positively correlated with all three measures of biological value (i.e., richness, endemism, non-species values), indicating that threats tend to be focused on the region's most important areas for biodiversity. Integrating biological values with threats allows identification of two distinct sets of ecoregion priority. First, highly imperilled ecoregions with many narrow endemic species that require focused actions to prevent the loss of further habitat leading to the extinction of narrowly distributed endemics. Second, less threatened ecoregions that require maintenance of large and well-connected habitats that will support large-scale habitat processes and associated area-demanding species. By bringing these data together we can be much more confident that our set of conservation recommendations serves the needs of biodiversity across Africa, and that the contribution of different agencies to achieving African conservation can be firmly measured against these priorities.

Abstract: This article sets out to examine the extent to which the South African government's land reform programme might provide a way out of poverty for its beneficiaries. The research was undertaken with two previously marginalised rural communities situated in the Northern Cape province of South Africa that had recently been granted land through the restitution and redistribution components of the programme. The results emphasised the low asset status of most households and their striking dependence upon public transfers, in particular old age pensions and disability grants. For better-off households, it is participation in paid employment that enables them to avoid poverty. The research demonstrates unequivocally that restituting or redistributing land that is geographically remote from the residence location of the beneficiaries, and with no service or technical support to assist them with start-up agricultural activities, provides no effective solution to reducing poverty in rural South Africa. Considering the current failure of the land reform programme to meet its poverty reduction objectives, this article proposes that land should only be made available to poor people in smaller quantities and near their homes so that they can utilise it with minimal outside support.

Abstract: High African elephant stocking rates in nature reserves in southern Africa have been shown to have significant impacts on vegetation structure and diversity. However, the direct and indirect effects of elephants on fauna, particularly invertebrates, remain poorly known. The Maputaland Centre of Endemism, an area of southern Mozambique and northern KwaZulu-Natal in South Africa, is undergoing rapid rates of habitat conversion. Sand Forest, the rarest vegetation type in the Centre, is threatened by human disturbance outside of protected areas and by elephant browsing pressure in Tembe Elephant Park, one of the few protected areas for Sand Forest. Here we examine the effects of elephant- and human-induced disturbance to Sand Forest on a functionally important component of invertebrate diversity, i.e. the dung beetle fauna. The dung beetle assemblage associated with elephant-disturbed Sand Forest was transitional between undisturbed Sand Forest and Mixed Woodland, whereas that associated with human disturbance was markedly different to either habitat type. Differences are attributed to a change in habitat structure under both disturbance types, as well as to changes in the quality and distribution of dung under human disturbance. Therefore, grazing impacts by elephant not only affect plant diversity, but also implement changes in invertebrate fauna. The maintenance of the integrity of the Sand Forest-Mixed Woodland matrix is considered critical for biodiversity conservation in the Maputaland Centre of Endemism. Management of elephant populations, as well as the protection of sufficient Sand Forest inside conservation areas must, therefore, necessarily form part of the conservation strategy for the Centre.

Abstract: Summary Poverty and environmental degradation seem to be endemic in many of the former homeland territories of South Africa. The political legacy of Apartheid might have ceased, but the economic and environmental consequences thereof still have to be dealt with. In one interesting case such a poverty-stricken and environmentally degraded area (Bushbuckridge) lies adjacent to a world conservation icon, the Kruger National Park. Currently, however, the community of Bushbuckridge does not enjoy much benefit from this unique geographic location. On the contrary there seems to be increasing tension between the community in their quest for survival and the national park as a conservation enclave. This tension will not disappear automatically. The situation needs to be managed. It is proposed here that by broadening the conservation corridor through land restoration and by incorporating the Bushbuckridge communal land as an IUCN Category VI protected area (a protected area within which sustainable resource harvesting by communities is permitted) into the Kruger National Park and under the provision that the community remains the land owner, the conservation initiative could benefit the community as much as by a factor of four. For this to be successful a proper managerial and institutional system will have to be in place, including a system that will allow the trade in ecosystem goods and services.

Abstract: The present aridity of Africa contrasts with the lush environments that existed over most of the continent in the early Cenozoic. The extinction of large terrestrial herbivores at the end of the Mesozoic, and relatively warm global climatic conditions in the early Cenozoic contributed to the spread of forests and woodlands in regions today occupied by grasslands and deserts. The increase in aridity after the Eocene climate optimum has been complex, characterized by multiple reversals and modulated by rifting in eastern Africa. The paleobotanical evidence indicates that ecological differentiation within the continent existed early in the Cenozoic, with some areas dominated by moist forests and others by drier Acacia woodlands. C4 grasslands began to spread during the Late Miocene, and became more prominent during the Pleistocene. In parallel to the spread of grassland mosaics during the Cenozoic there was an increase in the diversity of large herbivorous mammals (with body mass >350 kg). This diversity in megafauna peaked in the Pliocene. One of the key ecological roles of the megafauna was to create and maintain complex mosaics that included open habitats. Faunal evidence of paleoenvironments in the Turkana Basin of Kenya corroborates conclusions derived from other lines of evidence, but raises new questions. Hypsodont and cursorial bovids increased in abundance in the Late Miocene about 6 Ma, in the Pliocene after 3 Ma, and again in the Plio-Pleistocene after 2 Ma. But this faunal evidence also demonstrates that not all parts of the Turkana Basin responded in the same way to climatic changes. The lower Omo valley of Ethiopia, a northern extension of the Turkana Basin, remained significantly more forested than the areas near the western margins of the basin. Major river valleys like the Omo served as refuges and centers of endemism during intervals of significant climatic fluctuations. A similar role was played by the coastal and montane forests of eastern Africa, which were separated from the Central African forests by an arid corridor that stretched from northeast Africa to Namibia, and probably originated in the Miocene. The complex mosaic of environments in eastern Africa today continues to support an immensely diverse range of plants and animals, many of them found nowhere else on earth.

Abstract: Lake Urema is one of the most important ecological features of Gorongosa National Park, located in central Mozambique, in the East African Rift System. Understanding hydrology and ecology of the lake and its tributaries is particularly important for the conservation of the Park's floodplain habitats and its biodiversity. There are concerns that hydrological boundary conditions and ecology of Lake Urema have changed in recent years. Possible causes for this change include climatic and land use changes as well as tectonic and geomorphological processes. In this study, a multi-temporal and multi-disciplinary approach was applied to investigate the dynamics and control mechanisms of Lake Urema. Principal methods comprised remote sensing analyses of time series of Landsat and ASTER data, geomorphological interpretations of a Digital Terrain Model (DTM) as well as field investigations such as analyses of water quality and sediment composition. The waters of Lake Urema have a low mineralization and pH values approximately neutral. The spatially dominant sediment type has a pure clay texture consisting of kaolinite and smectite. The sandy type consists of quartz, kali felspar, and plagioclase. The results of the supervised classifications for the satellite images from 1979 to 2000 showed that the lake's extent ranged between 17 km2 (09/1995) and 25 km2 (08/1979). Above average rainfall was responsible for the extreme lake size in May 1997 (104 km2). The interpretations of the Digital Terrain Model demonstrated that alluvial fans limit the Urema basin from all sides and make Lake Urema a form of "reservoir lake". The control mechanisms of the hydrological regime of Lake Urema, such as the contribution of groundwater, are not yet fully understood. The lake's condition during the rainy season was not investigated. In the future, investigations of the sources and amounts of sediment input into the lake should be conducted.

Abstract: Soil erosion plots of different types and sizes are widely used to investigate the geomorphological processes related to soil erosion. This field method has provided a variety of results, depending on the characteristics of the plots, on their suitability to reflect the ecosystem's characteristics and on the objectives of each particular research. The coupling of real soil loss at patch and slope scale within a landscape and the values obtained by field plots depend, among other things, on how good the methodology performs over a set of ecosystem properties, such as those related with temporal and spatial scale issues, disturbance and representation of natural conditions, and the ability to account for the complexity of ecosystem interactions. Here, we present a review of (i) the advantages and limitations of the use of field plots to measure soil erosion; and (ii) the potential sources of variation in the results obtained due to a lack of harmony between methodological conditions and the processes operating in the environment at different scales. As regards the spatial and temporal scale of measurements, topics such as the exhaustion of available material within closed plots in long term measurements, the different erosion processes operating (and measured) at different spatial scales and the problems and alternatives of extrapolation of the results from larger to smaller scales, are the main causes of variation between measurements. The disturbance and inadequate representation of natural conditions, such as the heterogeneity, continuity and connectivity of factors and processes, are also sources of variation in the results of specific measurements. In short, the key factor is the difficulty to encapsulate the complexity of system interactions and to represent these interactions by means of field plots. The complexity concept is translated in the connectivity of water and sediment fluxes in the landscape and the interaction between processes and patterns of vegetation and surface components operating across scales.

Abstract: This study reviewed the distribution of ten common savanna trees in Namibia. Tree distributions were investigated in relation to bioclimatic, topographic and edaphic variables at a national scale. The factors of importance at these broad geographic scales appeared to be rainfall, substrate and, likely, the incidence of frost. Baikiaea plurijuga, Burkea africana, Guibourtia coleosperma and Pterocarpus angolensis seem to reach their bioclimatic limits in Namibia. At the local level, plant traits become important and contribute to explaining distribution patterns. High water and/or nitrogen use efficiency (Acacia erioloba, Colophospermum mopane), dual water obtaining strategies (Faidherbia albida), fire tolerance (e.g. Acacia species, Burkea africana and Pterocarpus angolensis) and drought tolerance (Boscia albitrunca) are some key attributes providing additional explanations for current distributions. Amongst the selected trees and at broad geographic scales, below-ground adaptations are governed by rainfall regime in combination with coarse-textured soils, whereby shallow-rooted trees prevail in the Kalahari sandveld. Deep-rooted species are found largely on non-sandy soils. Physiological performance of many trees appears to be directly linked to rainfall regime and trees may hence show varying performance throughout their distribution range. Insight into plant functional attributes of trees in Namibia is required to develop appropriate management strategies in the light of climate change. Modelling climate change impacts should consider the relative contribution of bioclimatic versus local environmental factors that explain the current distribution patterns of the selected trees.

Abstract: The high-altitude rangelands of the Trans-Himalaya represent a grazing ecosystem which has supported an indigenous pastoral community for millennia alongside a diverse assemblage of wild herbivores including burrowing mammals (pikas and voles). Pastoralists consider the small mammals to cause rangeland degradation and as competitors for their livestock, and actively eradicate them at many places. We present data on the ways in which small herbivores like pikas and voles mediate plant community dynamics. Vegetation cover and plant species richness were compared on and off both active and abandoned small mammal colonies. Plant species richness was higher inside colonies (about 4-5 species/plot) than outside (about 3 species/plot) whereas vegetation cover was only marginally lower (52% compared to 60%). Soil disturbance due to small mammals is seen to be associated with higher plant diversity without causing dramatic decline in overall vegetation cover. Such disturbance-mediated dynamics and vegetation mosaics produce a rich array of testable hypotheses that can highlight how small mammals influence assembly processes, succession, and dominance hierarchies in plant communities in this arid ecosystem. So, eradicating small mammals may lead to declining levels of diversity in this ecosystem, and compromise ecosystem-functioning. Changes in traditional pastoral practices and overstocking are more likely to be responsible for degradation. We emphasize that eradicating small mammals can lead to loss of diversity in this ecosystem and it is not a solution for the degradation problems.

Abstract: This paper defines a land cover classification technique based on the annual NDVI cycle. A similarity measure based directly on the components of the Discrete Fourier Transform is used to determine a pixels class membership. This Fourier component similarity measure produces an objective, computationally inexpensive and rapid method of classification that is able to classify rangeland vegetation by dominant shrub type, and which performs favorably compared to previously published classification techniques. By also defining a Fourier component based coverage measure this technique provides an estimate of vegetation coverage.

Abstract: This study presents first results on Normalized Difference Vegetation Index (NDVI), from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) sensor onboard the geostationary satellite Meteosat Second Generation (MSG) covering the African continent. With a temporal resolution of 15 min MSG offers complementary information for NDVI monitoring compared to vegetation monitoring based on polar orbiting satellites. The improved temporal resolution has potential implications for accurate NDVI assessment of the African continent; e.g. the increased amount of available scenes are expected to help overcome problems related to cloud cover which makes the MSG data particularly well suited for early warning systems. Time series of 2004 MSG NDVI was compared to MODIS (Moderate Resolution Imaging Spectroradiometer) Terra and Aqua NDVI for the Dahra site in the Senegalese Sahel, West Africa. It was found that NDVI was available for 82 days with multiple cloud free acquisitions per day during the growing season as compared to 47 days with information from either MODIS Terra or Aqua for that particular site. Differences in MSG SEVIRI and MODIS BRDF on a seasonal scale were found to influence the time series of NDVI for the test site; MSG NDVI being higher than MODIS in July-August and lower in October-November. Preliminary composite analysis suggests that the period of compositing to produce continent scale cloud free products can be reduced to ~5 days using MSG NDVI as compared to polar orbiting data. With the availability of diurnal reflectance information the significance of differences between the red and near-infrared wavelengths due to anisotropy become evident, causing diurnal variations in observed NDVI. Diurnal MSG NDVI was compared to in situ measured MSG NDVI at the test site in Senegal and the same "bowl-shaped" diurnal curve was found for a medium dense cover of annual grasses. The range in observed NDVI and time of diurnal minimum was different due to different viewing geometry. Daily minimum of in situ measured NDVI was around solar noon whereas minimum MSG NDVI occurs one hour prior to noon due to the test site location 12° west of the satellite sensor. Diurnal variation in observed NDVI was studied for a number of pixels characterized by different sensor view zenith angles and vegetation types. This analysis illustrated the diurnal NDVI dependency of illumination conditions, view angle and vegetation intensity and pinpoints the importance of proper BRDF modeling to produce daily values of MSG NDVI normalized for acquisition time, which will be the subject of a forthcoming paper.

Abstract: Identification of the factors that determine the variation in browse quality, as determined by their chemical composition, is an important step towards understanding herbivore distribution patterns. Therefore, the variation in leaf chemical composition (digestibility lowering compounds: condensed tannin and total polyphenol concentration, and nutrients: nitrogen and phosphorous concentration) was related to geomorphology, vegetation structure, and fire history, in mopane (Colophospermum mopane) open woodland in Kruger National Park. The results show that the principle drivers of foliar nitrogen, condensed tannins and total polyphenols differ from those for foliar phosphorus. Nitrogen, condensed tannin and total polyphenol concentrations are mainly determined by the effect of fire. The foliar concentration of phosphorus is mainly determined by parent material. This difference may be related to differences in the mobility of nitrogen and phosphorous in the soil.

Abstract: Global Climate Change (GCC) can bring about changes in ecosystems and consequently in their services value. Here we show that the urban population in Israel values the green landscape of rangelands in the mesic Mediterranean climate region and is willing to pay for preserving it in light of the expected increasing aridity conditions in this region. Their valuation of the landscape is higher than that of the grazing services these rangelands provide for livestock growers. These results stem from a Time-for-Space approach with which we were able to measure changes in biomass production and rainfall at four experimental sites along an aridity gradient.

Abstract: Despite fire cycles of increasing severity and frequency in the arid western U.S., very little empirical analysis has examined the success of plant seeding on arid rangeland following fire. This manuscript uses a unique dataset to assess causal factors underlying the measured densities, several years after fires, of: (1) unwanted invasive grasses, (2) seeded grasses, and (3) sagebrush, on rangeland in a western U.S. state. To accommodate various characteristics of the data, we employ trivariate tobit maximum likelihood estimation. Results indicate that the success of reseeding efforts is sensitive to the timing of and techniques used in reseeding, as well as whether grazing is allowed on the land. Our findings have broad implications for emergency fire rehabilitation management and policy for rangelands in the western U.S., as well as arid and semiarid rangelands elsewhere.

Abstract: Inventories of carbon stocks and projected changes at national scale are needed in the context of the Framework Convention on Climate Change (UNFCCC), but uncertainties in the necessary soil data remain large. Soil organic carbon (SOC) and inorganic carbon (SIC) reserves in Jordan were estimated using a revised 1:500 000 soil and terrain database, providing baseline data. The 95% confidence limits for the median, total stock of carbon to 1 m depth were estimated at 1877-1896 Tg C (Tg = 1012 g or million tonnes). About 7% thereof is organic, reflecting the predominantly arid conditions in the Kingdom. Many cultivated areas have been degraded by inappropriate management and overgrazing. An empirical approach that considers spatial data on climate, soil conditions and land cover was used to estimate the ecologically and technically feasible gains in SOC in Jordan's croplands over 25 years of sustained, adapted management. The projected gains for the reference scenario were estimated at 25-124 Gg C (Gg = 109 g or thousand tonnes). This would correspond to an estimated annual mitigation potential of < 0.5% of Jordan's CO2-C emissions from fossil fuels and land use change for 1990, the baseline year for Kyoto Protocol reporting. This exploratory study suggests that follow-up studies that use dynamic C-models should focus on scenarios for the conservation and rehabilitation of Jordan's degraded rangelands.

Abstract: In the last century, the grasslands of southern South America were rapidly converted to croplands, starting a fragmentation process that is still ongoing. Almost no information is available on the spatial patterns and environmental controls of these processes. Our objective was to characterize the degree of fragmentation and to analyze the environmental controls of landscape composition of the Río de la Plata grasslands, in southern South America. We classified land cover types using three Landsat TM scenes and we analyzed landscape structure using six metrics. Grassland is still the predominant land cover type in the Pampas, occupying 65.5% of the analyzed area. The abundance of the original land cover varied regionally, being higher in the south east (Flooding Pampa) and lower in the northern part of the area studied (Rolling Pampa). Landscape fragmentation was determined by crop production, therefore, was highest in the Rolling Pampa and lowest in the Flooding Pampa. The fragmentation patterns were associated to both climatic and edaphic factors. Fragmentation of native vegetation was mainly regulated by soil drainage, as in poorly drained soils, crop production is almost unfeasible.

Abstract: The natural ecosystems of the Northeast Region of Brazil (NEB) have experienced persistent drought episodes and environmental degradation during the past two decades. In this study, we examined the spatial heterogeneity and temporal dynamics of the NEB using a 20-year time series of Normalized Difference Vegetation Index (NDVI) observations, derived from the National Oceanographic and Atmospheric Administration (NOAA)-Advanced Very High Resolution Radiometer (AVHRR) instrument. A set of 12 000 spatially distributed NDVI values was analysed to investigate significant deviations from the mean-monthly values of the base period (1982-2001) in the study area. Various statistical analyses involving minimum, mean and maximum values, coefficient of variation (CV), standardized anomalies (Z-scores), and 36-month running mean were applied to monthly NDVI values to identify spatial and temporal variations in vegetation dynamics. We found strong seasonal oscillations in the vegetation-growing season (February-May) over the NEB study area, with maximum NDVI observed in April-May and seasonal variations, expressed by the CV, ranging from 14% to 32%. In addition, a consistent upward trend in vegetation greenness occurred over the period 1984-1990, and was strongly reversed in the subsequent period 1991-1998. These upward and downward trends in vegetation greenness followed an inter-annual oscillation of ~7-8 years. We also found that dry season peak (September) latitudinal variations in NDVI were 20-25% greater in 1991-1999 than 1982-1990 across the study region. The results of this study suggest that patterns in NEB vegetation variability were a result of the impact of enhanced aridity occurring over the last decade of the 20th century.

Abstract: Soil organic matter (SOM) and phosphorus (P) fractions play a key role in sustaining the productivity of acid-savanna oxisols and are greatly influenced by tillage practices. In 1993, a long-term experiment on sustainable crop rotation and ley farming systems was initiated on a Colombian acid-savanna oxisol to test the effects of grain legumes, green manures, intercrops and leys as possible components that could increase the stability of systems involving annual cereal crops. Five agropastoral treatments (maize monoculture--MMO, maize-soybean rotation--MRT, maize-soybean green manure rotation--MGM, native savanna control--NSC and maize-agropastoral rotation--MAP) under two tillage systems (no till-NT and minimum tillage-MT) were investigated. The effects of NT and MT on SOM and P fractions as well as maize grain yield under the five agropastoral treatments were evaluated. Results showed that soil total C, N and P were generally better under no-till as compared to minimum-tilled soils. While P fractions were also generally higher under no-till treatments, SOM fractions did not show any specific trend. Seven years after establishment of the long-term ley farming experiment (5 years of conventional tillage followed by 2 years alternative tillage systems), MT resulted into moderately higher maize grain yields as compared to NT. The MGM rotation treatment had significantly higher values of maize yield under both tillage systems (4.2 Mg) compared to the NSC (2.3 Mg ha-1). Results from this study indicate that the rotational systems (maize-soybean green manure and maize-pastures) improved the soil conditions to implement the no-till or minimum tillage systems on Colombian savanna oxisol.

Abstract: Unlike any other biome, savannas consist of both trees and grasses in a persistent and equitable manner. This unique mixture of two different life forms attracted scientific scrutiny for decades. Embedded in this body of research studies is bush encroachment that affects many overgrazed savannas. Despite scientific efforts, however, the underlying factors that shape the functioning of this biome and govern bush encroachment remain largely elusive. Terminalia sericea is one such encroaching woody plant at the expense of herbaceous layers in overgrazed areas of southern Africa. Recent studies indicated a potential link between rainfall amount and opportunistic rooting systems of encroaching species for harvesting near-surface soil water. This study was thus carried out to specifically test this theory in Etosha National Park across a rainfall gradient. A total of 31 T. sericea shrubs were excavated to examine their rooting systems. Results show that although all plants surveyed showed a shallow root system, only two out of 15 shrubs in the drier section of the park exhibited a taproot. In contrast, half of the 16 shrubs studied in the wetter part displayed a taproot. This suggests that T. sericea shrubs employ a rooting strategy attuned to local climatic conditions. A differential competition between woody plants and the herbaceous layers for soil water is thus variably enhanced, which might act as one of the feeding mechanisms for bush encroachment. Future ecological models of the savanna ecosystems should therefore recognise variation in the rooting characteristics of this, and possibly other bush encroaching plants, in response to precipitation.

Abstract: Traditional perennial ryegrass-white clover mixtures have limitations in combined productivity and quality that herbs like chicory may alleviate. This study examined the consequences on productivity and quality of as well as competition and facilitation after introducing chicory into varies ryegrass-legume-based pastures in a field study over three consecutive growing seasons. A cultivar of chicory, suitable for grazing, in pure stand was found to out-yield a pure stand ryegrass in terms of dry matter and nitrogen (N) accumulation but was found to yield similar to mixtures of chicory and ryegrass. The inclusion of chicory, increased N accumulation per area unit irrespective of associated leguminous species but had no effect (P > 0.05) on the combined dry matter yield of these mixtures as compared to the chicory-ryegrass mixture. Chicory was not found to co-exist well with associated fodder legumes but it co-existed well with perennial ryegrass. Determined by a direct 15N plant labelling technique, chicory transferred little N to associated legumes and under moderate soil N conditions it almost out-competed the white clover whereas lucerne was able to withstand the competition with birdsfoot trefoil as intermediate. Chicory and ryegrass did exchange N amounting to less than 5% of the receiver plants' N economy whereas the N transfer from the N-rich lucerne constituted 15% of the associated ryegrass' N economy but less (P < 0.05) of the chicory's N economy. These differences are ascribed to the species' root morphology and root zonation. Chicory accumulated large amounts of calcium, potassium, sodium and zinc but significant less of magnesium and manganese, irrespective of the N supply. In the case of sodium it was a short-term effect whereas calcium and possibly also sulphur, copper and zinc accumulation increased over time. It is concluded that chicory may improve the management of intensive dairy farms with a large N surplus because of the increase in productivity per unit area and N uptake efficiency and add significant improvements of the quality of the forage.

Abstract: An experiment was conducted to examine how milk yield capacity affects diet selection of pluriparous mixed-breed goats on rangeland. Diets of goats were examined using microhistological fecal analysis at the beginning, middle and end of a 5-month lactation. Throughout lactation (158 days) diets of low (47.8±2.9 l kg per lactation) or high (66.0±8.1 l kg per lactation) yielding does had similar levels of shrubs (40±15 vs. 41±12% across stages of lactation), forbs (25±7 vs. 27±9%) and grasses (34±10 vs. 32±13%). Goats with high levels of milk production used more (p<0.05) Buchloe dactyloides at the middle of lactation (7±4 vs. 4±3%) and less (p<0.01) Bouteloua gracilis at the end of lactation (4±3 vs. 9±1%) than low producing goats. The relationships between the levels of the main forage species in feces and milk production were not significant throughout lactation. At the end of lactation, milk fat decline as dietary Buddleja scordioides levels increased (r=-0.65; p<0.01). Milk protein increased with increased levels of Bouteloua curtipendula (r=0.54; p<0.01), Buchloe dacyloides (r=0.49; p<0.05), Croton dioicus (r=0.51; p<0.05), Atriplex canescens (r=0.60; p<0.01) and Larrea tridentata (r=0.46; p<0.05). Our results showed that differences in milk production levels did not lead to differences in resource exploitation of does. These data also indicate that milk yield throughout lactation was not associated to any particular forage consumed by goats, but milk constituents at the end of lactation were sensitive to the ingestion of some plants of this rangeland.

Abstract: The structure and typology of beef cattle farms from three autochthonous Spanish breeds (Avileña-Negra Ibérica, Morucha and Retinta) located in "dehesa" areas have been characterised from a survey including 130 farms. The questionnaire provided information on the structure of the farms, feeding practices, reproductive and sanitary management, production and commercialisation of the product. Descriptive statistics and multivariate analysis (multiple correspondences analysis and cluster analysis) were used to understand the relationships between variables and to establish farm typologies. We have found that the farms are large (an average of 125 cows and 548 ha), with an average stocking rate of 0.4 livestock unit/ha of agricultural area. Most of the farms are family managed, but with an important presence of external employees. Feeding depends largely on grazing, with seasonal supplementation. The presence of other livestock species, such horses, sheep and swine is frequent. The typology of the farms has been established on the basis of (1) farm size, (2) productivity of labour, (3) degree of specialisation, and (4) degree of extensification. Three groups of farms have been differentiated. The first group has followed a strategy of intensification of the system and includes the smallest farms. The second group is constituted by farms of intermediate size, very specialised in beef production. The third group includes large farms that have followed a strategy of extensification, complementing farm incomes by the exploitation of other livestock species.

Abstract: We present a model of household decision-making in Kazakhstan. Traditionally, long-distance livestock migration of livestock occurred in Kazakhstan's rangelands, exploiting seasonal differences in forage availability. After independence, the rural economy collapsed and migrations stopped. We use multi-agent system modelling to examine trade-offs in allocation of wealth between capital and flocks. Winter forage availability is the key determinant of overall livestock numbers, while availability and price of winter fodder is an important determinant of livestock sector productivity. Seasonal migrations are only likely to reestablish if distant pastures have very poor winter forage. Otherwise, as total flock size increases, larger herds are predicted to settle away from villages. These predictions match field observations.

Abstract: The aim of the study was to identify and classify the woodlands, bushland and grasslands of the Umkhanyakude Integrated Sustainable Rural Development Node (also known as Maputaland) into homogenous management units to assist with the natural resource audit and monitoring program initiated by the Department of Agriculture. The Node is situated in KwaZulu-Natal Province at the extreme northern border between South Africa and Mozambique. Two hundred and twenty-five surveys were conducted during March-July 2002 within 400 random plots created within ARCVIEW 3.2. Ecological data were analysed using multivariate ordination and classification techniques. Four broad plant communities within two geographically separated vegetation types were described. The Coastal Sandveld occurs on the coastal plain on recent arenaceous sediments. The Clay Thornveld occurs in the interior and is associated with a variety of terrain types and geological formations but predominantly rhyolite, basalt, shale and mudstones. Communities within the major vegetation types were differentiated based on climate (temperature and precipitation differences associated with differences in elevation and topography) and anthropogenic disturbances such as old fields, settlements and deforested plantations. The two major plant communities were subdivided into two sub-communities that can be used as management units since they have approximately the same physiognomy, grass composition and habitat characteristics. The four broad management units are the Acacia nilotica - Acacia karroo - Dichrostachys cinerea Community (Clay Thornveld); the Cissus rotundifolia - Enteropogon monostachyos (Valley Bushveld) Community; the Panicum maximum - Brachylaena discolor Community (Coastal Bushveld) and the Themeda triandra - Urelytrum agropyroides Community (Grass - Palmveld).

Abstract: Diffuse (Centaurea diffusa Lam.) and spotted knapweed (Centaurea maculosa auct. non Lam.) are damaging exotic plant invaders of North American rangelands. Although existing weed management techniques can successfully reduce negative impacts of knapweeds, these plants continue to spread in an unpredictable manner. The successful spread of knapweeds into native plant communities may be driven, in part, by interactions between these plants and native soil communities. This study was conducted to evaluate the relative benefit of native soil communities to two native plants and two knapweeds and to investigate the growth of these plants in soil from knapweed infestations and from adjacent native rangelands. Individual plants of bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) A. Löve), yarrow (Achillea millefolium L.), spotted and diffuse knapweed were grown in a greenhouse in field collected soil. The relative benefit of the native soil community was determined by comparing emergence and production of native plants and exotic knapweeds in autoclaved versus unautoclaved native rangeland soil. Emergence and production were also determined in the greenhouse for native plants and exotic knapweeds grown in soil collected from the core and perimeter of knapweed infestations and in soil from the adjacent, uninvaded native rangeland. The native soil community had a negative effect on the growth of bluebunch wheatgrass (P. spicata (Pursh) A. Löve) and diffuse knapweed, but a positive effect on spotted knapweed emergence. The interactions between yarrow (A. millefolium L.) and the native soil community were variable. The native soil community appears to be more beneficial to spotted knapweed than to the other plants studied, including diffuse knapweed. Therefore, it appears that two closely related knapweeds have very different interactions with soil biota and perhaps different strategies for invasion. Soil from diffuse and spotted knapweed infestations did not prevent growth of two native plants. Diffuse knapweed growth was not promoted by soil from within a diffuse knapweed infestation, but soil from the core of a spotted knapweed infestation did increase emergence of spotted knapweed.

Abstract: Patchiness is often considered a defining quality of ecosystems in arid and semiarid regions. The spatial distribution of vegetation patches and soil nutrients coupled with wind and water erosion as well as biotic processes are believed to have an influence on land degradation. A geostatistical measure of spatial "connectivity" is presented to directly measure the size of patches in the landscape from a raster data set. Connectivity is defined as the probability that adjacent pixels belong to the same type of patch. Connectivity allows the size distribution of erodible patches to be quantified from a remote sensing image or field measurement, or specified for the purposes of modeling. Applied to high-resolution remote sensing imagery in the Jornada del Muerto Basin in New Mexico, the spatial distribution of plants indicates the current state of grassland-to-shrubland transition in addition to processes of degradation in this former grassland. Shrub encroachment is clearly evident from decreased intershrub patch size in coppice dunes of 27.8 m relative to shrublands of 65.2 m and grassland spacing of 118.9 m. Shrub patches remain a consistent 2-4 m diameter regardless of the development of bush encroachment. A strong SW-NE duneland orientation correlates with the prevailing wind direction and suggests a strong aeolian control of surface geomorphology. With appropriate data sets and classification, potential applications of the connectivity method extend beyond vegetation dynamics, including mineralogy mapping, preserve planning, habitat fragmentation, pore spacing in surface hydrology, and microbial community dynamics.

Abstract: Millennial-scale climatic variations have punctuated the Holocene characterised by abrupt changes from warm to cool or wetter to drier conditions. Amongst these climatic events, there is increased evidence for an abrupt multicentennial shift of climatic conditions around 3.8/3.7 kyr BP (4.1 cal. kyr BP) in mid- to low-latitude regions which had a profound impact on landscape and population migration. In the Mediterranean region, subtropical, tropical and equatorial Africa, a number of continental proxies (lake-levels, pollen sequences, stable isotopes) record this abrupt change towards drier conditions. However, regionalism in climatic conditions is reflected in the vegetation records, possibly in relation to orographic conditions and the influence of sea-surface conditions. Hitherto there have been very few marine sequences that record this particular climatic shift at high-resolution. We present here new data from the Congo deep-sea fan containing integrated marine and terrestrial proxies. Around 5-4 cal. kyr BP, shifts in surface conditions off the Congo River mouth are observed, with possible establishment of seasonal coastal upwelling, and lower sea-surface temperatures. In parallel, pollen data indicate fluctuations of herbaceous, afromontane taxa and charred grass cuticles, suggesting more open vegetation in the lowland regions and an increase in cloud forest and/or afromontane vegetation at higher altitudes within the Congolese region.

Abstract: Soluble organic N and C were extracted from soils under long-term kikuyu grass pasture, annual ryegrass pasture and annual maize production using water, 0.5 M K2SO4 and 2 M KCl. Quantities extracted with K2SO4 were more than double those extracted with water while those extracted with KCl exceeded those using K2SO4. Differences in soluble organic C and N between land uses were much more obvious when water rather than salt solutions were used. It was suggested that water extracts give more realistic values than salt solutions. Regardless of the extractant used, the proportion of total N present as soluble N was considerably greater than the equivalent proportion of organic C present as soluble C. While the percentage of soil organic C and total N present in the light fraction and microbial biomass was lower in the kikuyu than ryegrass and maize soils, the equivalent values for water soluble C and N were, in fact, greatest in the kikuyu soil. The leaching of organic C, N and NO3- from these soils was also measured over a 6-month period in a greenhouse lysimeter study. The soils were either left undisturbed or were disturbed (broken into clods <50 mm diameter) to simulate tillage and stimulate microbial activity. Quantities of organic C and N leached were greater from the kikuyu than other treatments and tended to be greatest from the disturbed kikuyu soil. The percentage of total soil N leached as organic N was considerably greater than that of total organic C leached as soluble C. Leaching of NO3- was greatest from the disturbed kikuyu soil and least from the undisturbed kikuyu soil. The mean percentage of total soluble N present in organic form in leachates ranged from 17 to 32% confirming the importance of this form of N to leaching losses of N from agricultural soils.

Abstract: Predictions of species invasions are often made using information from their native ranges. Acquisition of native-range information can be very costly and time-consuming and in some cases may not reflect conditions in the invaded range. Using information from the invaded range can enable much faster modeling at finer geographic resolutions than using information from a species' native range. We used confirmed presence points from the native range, southern Africa, and the invaded range, the southwestern United States, to predict the potential distribution of the perennial bunchgrass Eragrostis lehmanniana Nees, (Lehmann lovegrass), in its invaded range in the United States. The two models showed strong agreement for the area encompassed by the presence points in the invaded range, and offered insight into the overlapping but slightly different ecological niche occupied by the introduced grass in the invaded range. Regions outside of the scope of inference showed less agreement between the two models. E. lehmanniana was selected via seeding trials before being planted in the United States and therefore represents an isolated genotype from the native-range population. Models built using confirmed presence points from the invaded range can provide insight into how the selected genotype is expressed on the landscape and considers influences not present in the native range. Models created from locations in both the invaded and native ranges can lead to a more complete understanding of an introduced species' potential for spread, especially in the case of anthropogenic selection.

Abstract: Land use change and livelihood systems are often analyzed separately or with one "driving" the other. This "driver-feedback" relationship has been buttressed by approaches to social process that are often far too static. Actors are confronted with a bundle of choices that they must negotiate as they create pathways of change. These choices are always bound up in relations of power and the knowledges that are the conditions for and results of these relations. We suggest that land uses and livelihood are different manifestations of the social processes by which individuals and groups negotiate the everyday conditions that shape their lives. We propose a framework that extends current understandings of the relationship between land use change and livelihoods by treating social relations of power as the entry point into this complex relationship. We underpin our arguments with empirical examples from South Africa and Ghana that locate power/knowledge relations in the context of social change in both study areas.

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Abstract: Herder knowledge of landscape classification and environmental assessments in East Africa has been poorly documented. This study investigated how the Maasai traditionally classified and assessed landscapes for grazing resources in northern Tanzania. The Maasai herders classified seasonally grazed landscapes using socio-cultural folk systems, soils, topography and vegetation, management knowledge and seasons of grazing. Herders characterized landscapes of the grazing lands as degradable (orpora) or non-degradable (orkojita) in response to heavy grazing pressure, with reference to soils (ngulupo) and vegetation type. This categorization is used for regulating seasonal grazing across heterogeneous landscapes. Impacts of livestock grazing across seasonal grazed landscapes were evaluated in terms of herder perceptions and field data on plant species composition, richness, biomass and cover. According to the herders, degradation occurred in the Selela landscapes when traditional grazing systems were altered by crop cultivation. Herders used past experiences to determine shifts in plant species composition. The disappearance of key forage species and an increase in species less desired by livestock were used as indicators of degradation. The overall effect of land degradation was inferred from a decline in livestock productivity. The evidence suggests that descriptions of landscape degradation in terms of loss of grazing value for a particular livestock species might be more relevant than a general statement about rangeland degradation associated with pastoral land use. According to these findings, land use planners could incorporate herder knowledge with scientific methods to test the impact of management and promote community participation in rangeland monitoring.

Abstract: Aeolian processes are tightly linked to soil and vegetation change in arid and semi-arid systems at multiple spatial and temporal scales. Wind influences patterns of vegetation and soil within the landscape, and these patterns control wind erosion at patch to landscape scales. Aggregated at larger scales, patterns in soil and vegetation distributions influence global distributions of dust and its biogeochemical impacts. Understanding the controls on aeolian processes is therefore important not only in understanding the biogeochemistry and land cover patterns in dryland environments, but also in understanding global land cover, climate, and biogeochemistry. Although the microscopic physics that control aeolian processes are well understood, the controls on these processes in real landscapes are poorly constrained, particularly for structurally complex plant communities such as shrub-invaded grasslands. This paper reviews the controls on aeolian processes and their consequences at plant-interspace, patch-landscape, and regional-global scales. Based on this review, we define the requirements for a cross-scale model of wind erosion in structurally complex arid and semi-arid ecosystems.

Abstract: An understanding of seasonal changes in pasture biomass, production and offtake of different range types is fundamentally important for the efficient management of livestock grazing. However, few studies have quantified these changes for transhumance systems, despite the fact that transhumance is still the main form of livestock management in several regions of the world and is often critical for the livelihoods of the people. One such area is the Northern Areas of Pakistan, where six villages and their pastures were selected for study. Pastures were categorized within foothill, dry temperate and alpine range types, and seasonal biomass, production and offtake of the vegetation was estimated by clipping paired caged and uncaged quadrats. The alpine range type had by far the highest biomass and offtake; the foothill and dry temperate range types were much more sparsely vegetated. Although alpine pastures were heavily used, particularly in spring, there was no evidence for consistent over-utilization of pasture resources. Within the dry temperate range type, production was highest during spring but significantly under-used. This indicates a potential for increased use of dry temperate pastures during spring, an important period both for early recovery of livestock body condition after winter and to reduce the heavy pressure on the alpine pastures at this time.

Abstract: Southern South America (SSA) has today a high diversity of climates, environments, biomes, and biotas, as a result of the complex interaction through time of plants and animals with the geological forces (e.g. plate tectonics, sea-level changes, glaciations) that modulated the geography of the continent. Arid biomes are well represented in SSA today, but were arid biomes similarly important in the geologic past? How long in time can be found major arid biomes in SSA? With the aim of replaying these questions, in this paper we summarized the paleoenvironmental changes of SSA through Cenozoic, emphasizing the relationships between biomes and the geological forces that, through different climatic-environmental factors, have driven its evolution. We define SSA the south of the 15°S area. We prefer this geographical delimitation because with it we can see and follow the history of the biogeographic (historic and ecologic) relationships of Patagonian biota with the rest of the South American biota. Additionally, with this delimitation we possess the most complete Cenozoic South American land-mammal fossil record. We use biomes because biomes are taxon-free analytical units, and their pattern of change can be traced through time independently of the taxa present at different geological periods. Data on plate tectonics, volcanism, sea-level changes, marine paleotemperatures, and glaciations were taken from literature. To analyse the pattern of change of southern South American climates and environments through the Cenozoic, we used the fossil record of land-mammals as information source. When available, the record of vascular plants were used to contrast the inferences derived from land-mammals. Finally, we used standard geologic divisions (i.e. Epochs) as chronological units. The main conclusion of this paper is that from Early Paleocene to Late Pleistocene, southern South American climatic conditions changed from warm, wet, and non-seasonal, to colder, dryer, and seasonal. Concomitantly, biomes changed from tropical forest to steppes, across a sequence constituted by subtropical forests, woodland savanna, park-savanna, and grassland savanna. During the Quaternary, and as a consequence of glacial cycles, cold and dry conditions were interrupted by warmer and wet periods. Accordingly, several pulses of expansion and retraction of steppes (and, concomitantly, advances and retreats of the northern tropical forests) are recorded. This cyclic pattern of changes produced the provincialism that has characterized the South American biota from Early Pleistocene to the present.

Abstract: The large global extension of arid and semi-arid regions together with their widespread degradation give these areas a high potential to sequester carbon. We explored the possibilities of semi-arid ecosystems to sequester carbon by means of rangeland exclusion and afforestation with Pinus ponderosa in NW Patagonia (Argentina). We sampled all pools where organic carbon accumulates in a network of five trios of adjacent grazed, non-grazed and afforested stands (age: 12-25 years, density 605-1052 trees ha-1). After 15 years since trees were planted, afforestation added ~50% more C to the initial ecosystem carbon pool, with annual sequestration rate ranging 0.5-3.3 Mg C ha-1 year-1. Carbon gains in afforested stands were higher above than below-ground (150% vs. 32%). Root biomass differences (374% more in afforested vs. grazed stands, p=0.0011) explained below-ground carbon contrasts whereas soil organic carbon showed no differences with afforestation. By contrast, grazing exclosures did not result in significant changes in the total carbon storage in comparison with the adjacent grazed stands (p=0.42) suggesting a slow ecosystem recovery in the time frame of this study (~15 years of exclusion). Nevertheless, higher litter amount was found in the former (+53%, p=0.07). Neither, soil organic carbon nor root carbon showed significant differences between grazed and non-grazed conditions. Considering that more than 1.1 millions of hectares of the studied ecosystems are highly degraded and suitable for tree planting, afforesting this area could result in a carbon sequestration rate of 1.7 Tg C year-1, almost 6% of the current fossil fuel emissions of Argentina; however environmental consequences which could emerge from this deep land use shift must be taken into account when afforestation program are being designed.

Abstract: This study was conducted in the arid Mediterranean Reserve located in northern Jordan, representing a continuous grazed arid rangeland ecosystem. Quantitative analyses on species diversity in addition to phytogeographical analysis were conducted. Some ecological parameters such as, life forms, growth forms, species density and frequency were investigated. A total of 93 vascular plant taxa belonging to 78 genera and 26 families were reported. This constitutes about 4.3% of the total flora of Jordan. Reported taxa include 13 species of grasses, 69 forbs and 10 shrubs and semi-shrubs. The botanical survey pointed to the presence of four rare species in Jordan. Plant species were classified into 28 functional groups. Pairwise correlation analyses among the most abundant species, showed that neutral associations dominated (75%) those communities, followed by positive associations (19%), while only (6%) showed negative association. Positive association may be attributed to direct facultative mutualism, or to physical environmental heterogeneity. Such a positive cooperation in the plant community can significantly maintain species diversity in adverse environments. The relationship between primary productivity and species richness showed a humpbacked pattern. Maximum richness corresponded to a biomass level of 300-400 g m-2. However, a sinusoidal curve-fitting model explained the relationship between graminoids biomass and species richness. These findings pointed to the adaptation of plant taxa to livestock grazing and to the small-scale spatial and environmental heterogeneity in arid Middle Eastern Mediterranean rangelands. Results suggest that optimal biodiversity conservation for the arid Middle Eastern grazing lands should consider their high level of spatial heterogeneity. Rangeland managers should adopt grazing plans that apply a range of grazing pressure across the area so as to maintain diversity at local and regional scales.

Abstract: Elevated levels of nitrate in streamwaters draining forested catchments in the eastern escarpment area of South Africa are thought to occur as a result of land use change from natural high altitude grasslands to plantation forestry. In this investigation, soil samples taken from similar pedosystems in adjacent (about 50 m from each other) forest and grassland ecosystems were tested for a range of properties in order to determine differences, which might indicate the reasons for elevated leaching of nitrate from forest soils in these areas. Soils were collected monthly in the summer season and analysed for pH, total nitrogen, total phosphorus, organic carbon and net nitrogen mineralisation rates. From the soils collected with depth (10 cm intervals), a saturated paste extract was prepared from which the major anions, cations, electrical conductivity, pH and the nitrate sorption were analysed. Three parent rock types were studied namely dolomite, mixed dolomite and quartzite and quartzite. Soil pH reduction of as much as 0.51 units was found, with the median pH of 4.30 and 4.07 for grassland and forest soils, respectively. There was a high level of soil organic matter in soils of dolomitic origin, followed by those of mixed dolomitic and quartzitic origin and finally by those of quartzitic origin. The general trend with respect to the changes in the total nitrogen, total phosphorus and the C:N ratio (P < 0.01) followed the trends shown by the soil organic carbon. The net rates of nitrogen mineralisation pointed significantly towards more rapid nitrogen mineralisation and nitrification rates in forest soils (average 0.9 [mu]g N g soil-1 day-1) than those under the adjacent grassland sites (average 0.3 [mu]g N g soil-1 day-1). This was more noticeable in the more clayey, dolomitic-derived soil at the beginning of the study period in September 2000. The concentration of water-soluble nitrate in the topsoil horizons in grassland soils was low (less than 0.2 mmol l-1) compared to that of the forest soils (up to 1.1 mmol l-1). The clearest nitrate sorption trends were provided from the graph representing the lowest level of nitrate addition (3.4 mmol/kg) in grassland soils. The results of this study suggest that afforestation has changed the capacity of the soils to retain nitrate. Nitrate leaching into streamwaters may impact on other land use activities in the lower reaches of the catchment.

Abstract: What is causing the increasing densities of native shrubs, or so-called [`]woody weeds', in some semi-arid pastoral lands and how might they be most effectively managed? This question has been on the rangeland policy agenda in Australia for more than one hundred years. This paper describes a fresh examination of this question using a systems approach. A key component of the approach involved [`]mapping the problem'. Using a systems-based approach, landholders developed four system diagrams broadly describing the ecology of woody weed re-occurrence, control options, property economics and management constraints with diagrams identifying how different factors related to, or influenced, each other. Agency personnel also constructed a system diagram describing institutional and regulatory constraints, and their interactions. Later, all these system diagrams formed the basis for an adaptive management model with capabilities for developing and quantitatively evaluating alternative management strategies relating to woody weeds. This model is called the Woody Weed Planner. The Woody Weed Planner contains mathematical relationships developed through field experimentation over the last 25-50 years covering the ecology of woody weeds, control options and control economics. These relationships enable the user to generate mathematical responses as a result of changing model parameters. A key component of the model is the ability to simulate the effects of alternative management responses given different rainfall scenarios. To enable this to occur, the Planner allows the user to replay historical rainfall patterns and ask the question "what impact will these have on woody weeds, stocking rates and economic performance on my property?"

Abstract: Degradation of semi-arid rangelands in the Argentinean Pampa due to increasing grazing intensity has been a growing concern among ecologist. Many studies document the impact of grazing on vegetation structure but little information is available on soil properties in these environments. The present study aims to establish some terms of reference for these range soils. Field studies were carried out to test the validity of selected soil chemical, physical and biological parameters for their capacity to discriminate soils according to quality under rangeland use. The selected data set includes total soil organic carbon (SOC), particulate organic carbon (POC), total N and P contents, dry aggregate size distribution, water stable aggregates and proctor maximum bulk density. Three soils (sand, sandy loam and loam) corresponding to different topographical situations and natural vegetation structure were sampled in 6 cm depth intervals up to 18 cm in bulk density cylinders, with six replicates in each site. Sun and shade vegetation communities were sampled separately. Standing biomass was determined and dry matter was analysed for N, P, Ca and Mg content. A positive significant relation between clay+silt content and SOC was found (R2=0.53) in the 0-6 cm depth. Topsoil SOC was related to standing biomass (R2=0.21), and POC showed a strong correlation with SOC (R2=0.94). The highest values of SOC and POC were found in the sandy loam, while the loam had the highest POC/SOC ratio. Aggregate size distribution especially of >8 and <1 mm fractions reflected textural differences. Vegetation communities differed in their POC contents and POC/SOC ratios, with higher values found in the soils under shade community. It was concluded that SOC, POC, POC/SOC ratio and aggregate fractions >8 and <1 mm are sensitive soil quality parameters that reflect differences of soil texture and vegetation community structure in range soils of this region.

Abstract: Colombian vegetation, at the ecological level of the biome, is reconstructed at six sites using pollen data assigned a priori to plant functional types and biomes. The chosen sites incorporate four savanna sites (Laguna Sardinas, Laguna Angel, El Piñal and Laguna Carimagua), a site on the transition between savanna and Amazon rainforest (Loma Linda) and a site within the Amazon rainforest (Pantano de Monica). The areal extent of tropical moist forest, tropical dry forest and steppe have been subject to significant change: differential responses of the vegetation to climatic shifts are related to changes in plant available moisture, duration of dry season and edaphic controls on the vegetation. The record from El Piñal shows that the present-day savanna vegetation, dominated by steppe (Poaceae) with little occurrence of woody savanna taxa (e.g. Curatella, Byrsonima), was present since the last glacial period of the northern hemisphere. Unfortunately, El Piñal is located on an edaphic savanna and is not particularly responsive to registering change. Most records cover the early Holocene; one site records the El Abra stadial (Younger Dryas equivalent), when forest expansion reflects more humid climatic conditions and higher plant available moisture. During the early and middle Holocene, the maximum expansion of steppe and tropical dry forest occurred, indicating that dry climatic conditions continued to around 4000 14C BP. The following period, from shortly before 4000 14C BP, is characterised by an increase in forest and gallery forests, reflecting a wetter period probably with a shorter annual dry season. Anthropogenic influence on the vegetation is recorded by all the records over the last millennial, particularly characterised by a reduction in forest cover and high amplitude changes in vegetation. Biome transitions from one type to another, and the environmental controls on this shift, are investigated by applying a vegetation model (BIOME-3). The model uses climatic data from six meteorological stations that, encompass a range of environments within lowland Colombia, which are similar to the pollen data. The signals of vegetation change can be translated to the main environmental controls of temperature and moisture to indicate the degree of change needed in these parameters to record the vegetation change depicted by the pollen data. Moisture balance is the dominant control on driving vegetation change whether under seasonal or annual control. The combined reconstruction from pollen data and model output of biome-scale vegetation dynamics for lowland Colombia allows an understanding of the environmental controls to be developed.

Abstract: The need to implement sustainable resource management regimes for Australia's extensive grazing lands is acute. Proposed solutions for promoting sustainable management typically seek to strike a balance between ecological and economic imperatives required to maintain the function of local ecosystems and to preserve the economic viability of the grazing enterprises. This paper explores some issues associated with the challenges of balancing ecological and economic objectives for the sustainable management of grazing lands. Some broad economic and ecological trends that might create conflict in defining sustainable management systems are considered. Prospective changes in resource use that may arise in response to these trends are also considered, along with barriers and opportunities that might retard or progress those changes. Some economic data, drawn from a case study of four grazing properties in the grassy woodlands of Queensland, are presented to highlight the difficulties of achieving an appropriate balance of ecological and economic outcomes for landscape management. Poor economic prospects and a range of practical management issues are apparent barriers to changing present practices on private land. Collective action to reduce the unit cost of management options also appears to offer little immediate attraction to landholders. Limited markets for conservation services and institutional constraints also impede the achievement of a better balance between economic and ecological objectives. Some suggestions are made on how to improve the prospects for adoption of sustainable land management practices.

Abstract: In this paper, we develop an original statistical method to infer palaeoenvironmental conditions from fossil taxonomical assemblages based on the present-day observed environmental characteristics of these taxa. We illustrate this method by analysing present-day and Holocene African bovid (Artiodactyla, Mammalia) species assemblages. Firstly, the modern bovid species occurrences in African environments ranging from tropical rainforest to desert are compiled in order to define the environmental characteristics of each species analysed. Secondly, these modern characteristics are considered in order to construct a statistical model of prediction of actual environmental conditions from the sets of most likely environments associated with each present-day location (station). The model then allows us to infer palaeoenvironmental conditions associated with archaeozoological evidence of 53 Holocene localities from Western Africa. Our results show that a tree cover was well established near rivers and uplands, and constituted refuge areas for human occupation during times of climatic desiccation. This conclusion is discussed in the climatic, environmental and archaeological contexts of the Holocene evolution and prehistory of Western Africa.

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Abstract: The carbon isotopic composition ([delta]13C) of plants can reveal the isotopic carbon content of the atmosphere in which they develop. The [delta]13C values of air and plants depend on the amount of atmospheric fossil fuel CO2, which is chiefly emitted in urban areas. A new indicator of CO2 pollution is tested using the [delta]13C variation in a C4 grass: Eleusine indica. A range of about 4[per mille sign] delta units was observed at different sites in Cotonou, the largest city in the Republic of Benin. The highest [delta]13C values, from - 12[per mille sign] to - 14[per mille sign], were found in low traffic zones; low [delta]13C values, from - 14[per mille sign] to - 16[per mille sign], were found in high traffic zones. The amount of fossil fuel carbon assimilated by plants represented about 20% of the total plant carbon content. An overall decrease in plant [delta]13C values was observed over a four-year monitoring period. This decrease was correlated with increasing vehicle traffic. The [delta]13C dataset and the corresponding geographical database were used to map and define zones of high and low 13C-depleted CO2 emissions in urban and sub-urban areas. The spatial distribution follows dominant wind directions, with the lowest emission zones found in the southwest of Cotonou. High CO2 emissions occurred in the north, the east and the center, providing evidence of intense anthropogenic activity related to industry and transportation.

Abstract: Summary The Okavango basin comprises the Cuito and Cubango active catchment areas in Angola, in addition to the Kavango-Okavango non-active catchment in northern Namibia and Botswana. The Okavango River water and its ecosystem resources are critically important sources of livelihoods for people in the basin. Pressures from livelihoods and development are already impacting on the environment. These pressures may increase in the future due to the rapid increase in population, the peace process and associated resettlement activities in Angola, and major development initiatives in Botswana and Namibia. For instance, possible future increase in water abstraction from the Okavango River may affect the long-term environmental sustainability of the Okavango Delta by minimizing channel shifting and thereby reducing spatial biodiversity. The paper argues that while conservation of the natural environment is critical, the pressing development needs must be recognized. The reduction of poverty within the basin should be addressed in order to alleviate adverse effects on the environment. The paper recommends that the development of sustainable tourism and community-based natural resource management initiatives may be appropriate strategies for reaching the Millennium Development Goals of poverty alleviation and achievement of environmental sustainability in the Okavango Basin. These initiatives have a comparative advantage in this area as demonstrated by the performance of the existing projects.

Abstract: Remote sensing has successfully been applied to map the distribution of canopy dominating invasive species. Many invaders however, do not dominate the canopy, and remote sensing has so far not been applied to map such species. In this study, an indirect method was used to map the seed production of Chromolaena odorata, one of the world's 100 worst invasive species. The study was executed in lowland Shorea robusta forest in Nepal, where Chromolaena invaded the understorey of degraded forest. A Landsat ETM+ image processed through a neural network predicted 89% and 81% of forest canopy density and light intensity reaching the understorey, respectively. We inverted these models to predict Chromolaena seed productivity. Light intensity determined 93% of the variation in log10 seed production per plant. Chromolaena failed to produce seed below a light intensity of 6.5 mJ m-2 day-1. Further analysis revealed that Chromolaena was absent above this light intensity in case of a high biomass of other shrub and herb species, a situation occurring in the absence of grazing. We therefore suggest that other species control Chromolaena through competitive exclusion in the absence of grazing, whereas grazing breaks the dominance of these other species thus creating the conditions for Chromolaena attain canopy dominance. The presence of grazing was related to distance from the forest edge, a variable that together with light intensity allowed us to map 64% of variation in Chromolaena cover. Predicted Chromolaena cover and seed production per plant were combined into a map displaying the total seed production per unit area. Such map displaying seed producing sites could be used to significantly reduce the costs of controlling Chromolaena infestation by providing information on the spatial segregation of source and sink populations, which will support efficient habitat ranking to restore invaded areas and protect non-invaded ecosystems. This may prove particularly valuable when implementing control measures under circumstances of limited capital and manpower.

Abstract: Savannah (C4) grasses are first recorded at low latitudes in the mid-Miocene prior to their expansion towards mid-latitudes by approximately the Miocene-Pliocene boundary. In an attempt to determine the timing of the spread of savannah grasses into the South African highveld, a palaeoecological study of some of the oldest faunal deposits in the region (mid-Pliocene) was undertaken. The combination of carbon isotope and dental microwear analysis of micromammals from the Rodent Corner and the Exit Quarry repositories of the Makapansgat Limeworks has enabled the determination of the relative proportions of C4 grass, C3 grass and C3 browse in the diets of two extinct herbivorous rodent species, Otomys cf. gracilis and Mystromys cf. hausleitneri. M. cf. hausleitneri is shown to have a similar diet to the extant Mystromys albicaudatus whereas O. cf. gracilis is shown to be less reliant on grazing than the extant Otomys irroratus, despite its specialised hypsodont molars. The lack of a grazing specialist amongst the most common species in the Makapansgat micromammal assemblages is suggestive of a local palaeo-environment that was more wooded than the present day woodland-savannah mosaic. The presence of C4 grasses in the mid-Pliocene of Makapansgat indicates that the spread of C4 grasses into the South African highveld occurred prior to this time.

Abstract: The direction, complexity and pace of rural change in affluent, western societies can be conceptualized as a multifunctional transition, in which a variable mix of consumption and protection values has emerged, contesting the former dominance of production values, and leading to greater complexity and heterogeneity in rural occupance at all scales. This transition is propelled by three dominant driving forces, namely: agricultural overcapacity; the emergence of market-driven amenity values; and growing societal awareness of sustainability and preservation issues. Australia's generous supply of land and sparse investment in agriculture has facilitated local transitions towards enhanced consumption and protection values, enabling a clearer delineation of emerging differentiated modes of rural occupance than in more contested locales. In Australia seven distinctive modes of occupance can be identified, according to the relative precedence given to production, consumption or protection values. These modes are described as: productivist agricultural; rural amenity; small farm (or pluriactive); peri-metropolitan; marginalized agricultural; conservation; and indigenous. Within these seven modes, alternative trajectories are identified, indicating variability in the intensity and type of resource use. Articulation of the transition concept may provide synergy between discrete discourses in rural research.

Abstract: In arid and semi-arid rangelands of sub-Saharan Africa, livestock are a central component of rural livelihoods and national economies, but their production is constrained by drought and disease, and exacerbated by institutional barriers and land use restrictions among other factors. Veterinary interventions may make a major difference to production measures but as with any intervention, they can also entail complex ecological and economic implications. This paper analyses the impacts of a vaccination programme for East Coast fever (ECF). ECF is the major cause of death among calves of Maasai pastoralists and agro-pastoralists and a major constraint on the livelihoods of these people. In our study sites, overall annual mortality in the calf crop due to ECF ranges from 30% to 60% depending on the rainfall (the better the rains, the higher the ECF mortalities). Our study explores the implications of vaccination for pastoralist livestock production, development and poverty and considers the potential impacts on rangeland and wildlife. Livestock mortality, sale, slaughter and exchange were measured using a multi-round survey of 72 households and a register of 1528 cattle in two study areas of different ecology and epidemiology. Livestock performance differed between the two areas, with the highland area showing higher background levels of mortality of unvaccinated animals. The infection-and-treatment method of vaccination has a major and highly significant impact on survival in both areas. Uptake of vaccination is strongly associated with a measure of wealth that includes livestock numbers and economic security, and medium and poor pastoralist households find it hard or impossible to access the full benefits of the vaccine. In one study site, vaccination was more frequent for male animals than females, suggesting an investment in vaccination for improved terms of trade. Vaccination could therefore improve livestock production without driving increasing herd numbers. However, the degree to which increasing survival due to vaccination is offset by increasing volume of trade requires further monitoring as those calves vaccinated at the start of the project reach economic maturity. Our study shows no link between vaccine uptake (or volume of trade) and scale of cultivation, suggesting little cross-investment between these livelihood activities. Vaccination potentially holds positive implications for rangeland and wildlife ecology. However, the logistics and economics of access to the vaccine mean that, under the current system of distribution, it could be driving socio-economic differentiation, rather than alleviating poverty. Alternative systems are suggested. Government and donor promotion of this and comparable interventions need to consider the poverty impacts and take measures to widen access.

Abstract: After a review of the first steps in marine palynology, we show that the understanding of the northwest African setting is crucial to evaluate the potential of marine palynological studies elsewhere. We studied distribution patterns of pollen grains in recent marine sediments off NW Africa and were able to clearly relate patterns to modern pollen source areas (vegetation belts) and operating transport systems (wind belts and ocean currents). In particular patterns of Quercus, Artemisia, Chenopodiaceae-Amaranthaceae, Ephedra, Gramineae, and wet forest trees are very indicative of the position of the vegetation belts on the adjacent continent. Aeolian pollen transport is carried out by the northeast trade winds and the African Easterly Jet (AEJ). In the rain forest belt transport of pollen and fern spores also occurs by rivers. A detailed comparison between recent pollen rain samples from terrestrial and marine sites between 21 and 12°N showed that the latitudinal range of vegetation belts is clearly reflected in the pollen samples of both environments. A migration of the southern border of the Sahara is reflected by the changing ratio between Chenopodiaceae-Amaranthaceae pollen from the desert and Gramineae pollen from the savannah belt. Distribution patterns of pollen for 9000 and 18,000 14C yr BP (last glacial maximum) time-slices, based on pollen records from eleven marine cores between Portugal and the Gulf of Guinea show significant latitudinal migrations of vegetation belts, but a stable position of the main wind trajectories. The AEJ had a stable position around 21°N. The belt with trade winds had a stable position from Morocco southwards. Changing vigour of the trade winds is clearly reflected by the patterns of isopollen contours and by changes in pollen influx records.

Abstract: Governance structures in Botswana are highly centralized and top-down in orientation. For water and related resources management in rural areas, this creates particular difficulties - from lack of decision-making capacity to limited human and financial capital at the level of the resource base. In Ngamiland, government is currently undertaking the Okavango Delta Management Plan project as part of its commitment to the Ramsar Convention on Wetlands. The project purports to develop an integrated management plan based on an ecosystems approach. Meaningful participation by local people is a requirement of the process. Data from 43 village meetings undertaken under the auspices of the ODMP process reveal that local people's access to their resource base is diminishing. Information from key informant interviews and a variety of government documents, however, suggests that policy makers are either unaware of or uninterested in this growing problem. Although citizens and government are engaged in an on-going dialogue, there is little evidence to suggest that policy and practice are moving toward sustainable solutions for all. This article highlights these issues in the hope that a more meaningful dialogue among all stakeholders may be undertaken.

Abstract: Abstract 10.1002/ldr.733.abs One of the many contentious issues facing the appropriate and accurate assessment of land degradation is the varying emphasis placed on vegetation degradation and soil degradation processes. This has led to the compartmentalization of land degradation assessment methods, depending on the particular perspective adopted. The land degradation assessment method presented here attempts to take into account both vegetation and soil degradation. This methodology is applied to the southern part of the Monduli District of northeast Tanzania, an area typifying the so-called �affected drylands� of Africa. Three sets of land cover maps synchronized against long-term rainfall data (1960s, 1991 and 1999) were used to assess land degradation in the area. Utilizing these three sets of land cover maps as a basis for change detection, it is possible to distinguish areas that experienced changes in vegetation due to rainfall variability from those areas that were subject to changes consequent upon anthropological factors. All areas that displayed overall depletion of natural and semi-natural vegetation due to human factors were deemed to have undergone land degradation, whereas areas that experienced inter-annual land cover changes due to rainfall variability were classified as experiencing cover change due to ecosystem dynamics. This method provides a complete and appropriate assessment of land degradation in the study area and can be used to improve degradation assessment in other semiarid areas. Copyright © 2006 John Wiley & Sons, Ltd.

Abstract: Woody plant invasion of grasslands is prevalent worldwide. In the Rio Grande Plains of Texas, subtropical thorn woodlands dominated by C3 trees/shrubs have been replacing C4 grasslands over the past 150 yr, resulting in increased soil organic carbon (SOC) storage and concomitant increases in soil total nitrogen (STN). To elucidate mechanisms of change in SOC and STN, we separated soil organic matter into specific size/density fractions and determined the concentration of C and N in these fractions. Soils were collected from remnant grasslands (Time 0) and woody plant stands (ages 10-130 yr). Rates of whole-soil C and N accrual in the upper 15 cm of the soil profile averaged 10-30 g C m-2 yr-1 and 1-3 g N m-2 yr-1, respectively, over the past 130 yr of woodland development. These rates of accumulation have increased soil C and N stocks in older wooded areas by 100-500% relative to remnant grasslands. Probable causes of these increased pool sizes include higher rates of organic matter production in wooded areas, greater inherent biochemical resistance of woody litter to decomposition, and protection of organic matter by stabilization within soil macro- and microaggregates. The mass proportions of the free light fraction (<1.0 g cm-3) and macroaggregate fraction (>250 [mu]m) increased linearly with time following woody plant invasion of grassland. Conversely, the mass proportions of free microaggregate (53-250 [mu]m) and free silt+clay (<53 [mu]m) fractions decreased linearly with time after woody invasion, likely reflecting stabilization of these fractions within macroaggregate structures. Carbon and N concentrations increased in all soil fractions with time following woody invasion. Approximately half of the C and N accumulated in free particulate organic matter (POM) fractions, while the remainder accrued in stable macro- and microaggregate structures. Soil C/N ratios indicated that the organic C associated with POM and macroaggregates was of more recent origin (less decomposed) than C associated with the microaggregate and silt+clay fractions. Because grassland-to-woodland conversion has been geographically extensive in grassland ecosystems worldwide during the past century, changes in soil C and N storage and dynamics documented here could have significance for global cycles of those elements.

Abstract: Soil physical structure causes differential accessibility of soil organic carbon (SOC) to decomposer organisms and is an important determinant of SOC storage and turnover. Techniques for physical fractionation of soil organic matter in conjunction with isotopic analyses ([delta]13C, [delta]15N) of those soil fractions have been used previously to (a) determine where organic C is stored relative to aggregate structure, (b) identify sources of SOC, (c) quantify turnover rates of SOC in specific soil fractions, and (d) evaluate organic matter quality. We used these two complementary approaches to characterize soil C storage and dynamics in the Rio Grande Plains of southern Texas where C3 trees/shrubs ([delta]13C=-27[per mille sign]) have largely replaced C4 grasslands ([delta]13C=-14[per mille sign]) over the past 100-200 years. Using a chronosequence approach, soils were collected from remnant grasslands (Time 0) and from woody plant stands ranging in age from 10 to 130 years. We separated soil organic matter into specific size/density fractions and determined their C and N concentrations and natural [delta]13C and [delta]15N values. Mean residence times (MRTs) of soil fractions were calculated based on changes in their [delta]13C with time after woody encroachment. The shortest MRTs (average=30 years) were associated with all particulate organic matter (POM) fractions not protected within aggregates. Fine POM (53-250 [mu]m) within macro- and microaggregates was relatively more protected from decay, with an average MRT of 60 years. All silt+clay fractions had the longest MRTs (average=360 years) regardless of whether they were found inside or outside of aggregate structure. [delta]15N values of soil physical fractions were positively correlated with MRTs of the same fractions, suggesting that higher [delta]15N values reflect an increased degree of humification. Increased soil C and N pools in wooded areas were due to both the retention of older C4-derived organic matter by protection within microaggregates and association with silt+clay, and the accumulation of new C3-derived organic matter in macroaggregates and POM fractions.