GSSA-Publications-2003

Abstract: China is rich in bamboo resources which contain 400 odd species of 30 genera, and among the countries that have the most bamboo species and the largest yields in the world. For thousands of years, bamboo has glittered in Chinese culture, arts and daily life. It is an important component of Chinese traditional culture. Generations of Chinese bamboo processing masters, through persistent inventive exertion for numerous years, have developed a unique bamboo processing art. Chinese bamboo processing art combines the traditional philosophical essence with national life style, it takes root from the daily life, and expresses more distinctive existence than that in daily life, offering aesthetic enlightenment and imagination. The aim of this book is to show the charm and elegant demeanor of bamboo art, not only find its place in history, but also make this traditional art carried forward, innovated and developed.

Abstract: Published studies relating erosion and productivity have been generally based on information derived from expert opinion on the extent and severity of soil erosion and on limited data on its impact on soil productivity, resulting in widely varying yield and economic loss estimates. In contrast, this report estimates the impact of soil erosion on productivity by collating, synthesizing and comparing the results from published site-specific soil erosion-productivity experiments at a global scale. Using crop yield as a proxy measure for soil productivity, this analysis uses the data from 179 plot-level studies from 37 countries identified in the soil science literature to calculate absolute and relative yield losses per Mg or cm of soil erosion for various crops, aggregated by continent and soil order. The results show that effects of past erosion on yields differ greatly by crop, continent and soil order. However, aggregated across soils on the continental level, absolute differences in productivity declines Mg-1 of soil erosion are fairly small. However, depending on the specific crop and soil, relative erosion-induced yield losses Mg-1 or cm-1 of soil erosion were two to six times smaller in North America and Europe than in Africa, Asia, Australia and Latin America. The higher losses in the latter continents are due primarily to much lower average yields, so that with identical amounts of erosion, yields decline more rapidly in relative terms. Studies using management practices as their experimental method to determine effects of present erosion showed much greater absolute and relative yield losses, which may be an artefact of the combined effect of erosion and variable management practices. Comparing the results of past and present erosion studies indicates that inappropriate soil management may amplify the effect of erosion on productivity by one or several orders of magnitude. Good soil management for effective erosion control and maintaining productivity, therefore, is imperative to meet the needs of the world's present and future population.

Abstract: East Africa contains areas with some of the greatest large mammal biodiversity on the planet. These areas are key natural resources for the economic development of the region. They are also key areas for pastoralists who have co-existed with wildlife for millennia. Increasing populations, conflicts between wildlife and cattle, and the growth of agriculture, are all placing great pressure on these lands This paper describes the development of a pastoralist socio-economic model that is linked to the Savanna ecosystem model. In this way, options and scenarios could be investigated for their impacts not only on the ecosystem but also on pastoralist households and their welfare. The model, named PHEWS (Pastoral Household and Economic Welfare Simulator), tracks the flow of cash and dietary energy in pastoralist households using a simple set of rules. The model was calibrated for the Ngorongoro Conservation Area (NCA), northern Tanzania. The results of two population increase scenarios are presented. Model results indicate that all households in NCA depend to some degree on outside sources of calories, and that pastoralist welfare in NCA, even with small amounts of agriculture allowed, is under severe pressure at current human population levels. Strengths and weakness of the model are discussed, and next steps in its application identified.

Abstract: Summary * 1The success of large-scale cattle ranching in African savanna vegetation has often been limited by problems of bush encroachment and disease (in particular trypanosomiasis spread by tsetse flies). Mkwaja Ranch, occupying an area of 462 km2 on the coast of Tanzania, is a recent example of a large ranching enterprise that failed within the savanna environment. It was closed in 2000 after 48 years of operation. In this paper we describe the main vegetation types of the area (excluding closed forest vegetation) and relate their patterns of distribution to the former use of the ranch for cattle. * 2The study area comprised the former ranch and parts of the adjacent Saadani Game Reserve, which had not been grazed by cattle for many years and had never been used for large-scale ranching. Following field surveys, 15 distinct types of grassland and bush vegetation were defined and a vegetation map was created using a Landsat TM satellite image. A multispectral classification using the maximum likelihood algorithm gave good results and enabled all 15 vegetation types to be distinguished on the map. * 3Two main spatial trends were detected in the vegetation. One was a large-scale decrease in the cover of bushland from the most intensively used parts of the ranch through more extensively used areas to the game reserve; this trend was attributed to differences in management history as well as to climatic and topographic factors. A second trend was a radial vegetation pattern associated with the enclosures where cattle were herded at night. High amounts of three bushland types [dominated by (i) Acacia zanzibarica, (ii) Dichrostachys cinerea, Acacia nilotica or Acacia mellifera and (iii) Terminalia spinosa] occurred in a zone between 300 and 2500 m from the paddocks, with a peak in bush density at about 900 m (mean value for 18 paddocks). In contrast, bushland dominated by Hyphaene compressa was scarce close to the paddocks and became more abundant with distance. There was also a radial trend in the grassland communities: close to the paddocks there was short grass vegetation containing many ruderals and invasive weedy species, while the tall grassland types with species such as Hyperthelia dissoluta and Cymbopogon caesius occurred further away in the areas less affected by cattle. * 4Synthesis and applications. The intensive modern livestock ranching as practised on Mkwaja Ranch proved to be unsustainable both economically and ecologically. In the end, the biggest problem faced by the ranch managers was not controlling disease, as had originally been feared, but preventing the spread of bush on pasture land. The results of our study demonstrate just how severe the problem of bush encroachment was, especially in areas close to paddocks. An important lesson for management is that grazing patterns need to be taken into consideration when determining the sustainable stocking rate for an area. To reduce the risk of bush encroachment in grazing systems with focal points such as paddocks or watering points, stocking rates need to be lower than in systems with a more uniform grazing distribution.

Abstract: South Africa is rich in biological diversity, but measures to conserve this heritage are under-funded and are of relatively low priority at national level. Part of the problem is that the social value of biodiversity is unknown, and thus the potential impact of a loss of biodiversity on social wellbeing is not recognised. Some of these threats, particularly climate change, are predicted to have major impacts on biodiversity within the next 50 years. This study investigates the public interest, experience and knowledge of biodiversity and uses contingent valuation methods to estimate its existence value, with emphasis on the internationally significant fynbos biome in the Western Cape. More than half of respondents classified themselves as actively or passionately interested in nature, and a high proportion had recently visited major nature reserves. Interest was correlated with knowledge, and both were positively correlated with willingness to pay (WTP) for biodiversity conservation, though WTP was constrained by income level. WTP for conservation was relatively high ($3.3 million per year for fynbos, $58 million for national biodiversity), and comparable with government conservation budgets. WTP increased dramatically (to up to $15 million and $263 million per year, respectively) when respondents were faced with the predicted impacts of climate change on biodiversity. The latter is probably a better estimate of the full existence value of biodiversity, since respondents were faced with absolute losses rather than, say, the reduction in species diversity.

Abstract: Overoptimistic stocking rates are the leading cause of rangeland degradation. The phenomenon of patch-selective grazing means that the stocking rate on heavily used patches is much higher than that intended for the area as a whole. In addition, the differential use of preferred areas in the landscape results in uneven distribution of animal impact. Landscape heterogeneity increases as grazing unit size increases, resulting in heavier impact on preferred areas. Such phenomena compound over time and have a major long-term impact on the environment and primary and secondary production. This study investigates whether rotational grazing allows reduction of, and recovery from, degradation caused by patch-selective grazing in large (1800-2100 ha) paddocks by providing adequate rest between grazing events. From 1995 through 1998, herbaceous basal area and bare ground changes were measured on adjacent heavily and lightly grazed patches in rotationally and continuously grazed paddocks. Although weather was a dominating influence (p[less-than-or-equals, slant]0·0001), the eight-pasture rotation system resulted in greater perennial herbaceous basal area (p = 0·0987) and lower proportions of bare ground on bottomland soils (p = 0·03) and clay-loam soils (p = 0·052) than the continuously grazed control. The increases in basal area with rotational grazing were primarily due to increases in perennial C4 mid- and shortgrasses. Grazing treatment did not influence species aerial biomass composition (p>0·1). This study provides evidence that in large paddocks, rotational grazing allows recovery from and reduces degradation caused by patch overgrazing. Planned rotational grazing addresses the root cause of patch overgrazing and deterioration. It is, therefore, a key tool in managing for sustainable use and restoration of rangeland.

Abstract: This paper estimates the preferences of farmers for cattle traits in southern Burkina Faso using conjoint analysis, a survey-based system for measuring preferences for multiple-attribute goods. Here the technique is used in the context of a West African country where literacy is low, where cattle perform multiple functions, where low-input management is the norm, and where cattle are exposed to a number of tropical diseases and other environmental stresses. The results reflect the production practices of the region, suggesting that important traits in developing breed improvement programs should include disease resistance, fitness for traction and reproductive performance. Beef and milk production are less important traits. The study shows the potential usefulness of conjoint analysis for quantifying preferences in less developed countries for livestock and for the wide variety of other multiple-attribute goods. One implication is that conjoint analysis provides a quantitative methodology that helps make diverse livelihood strategies more operational. Distinguishing differences in preferences between groups of respondents in connection with specific agro-ecological zones and production systems can be used to promote conservation-through-use of breeds at risk of extinction.

Abstract: A new diatom record from Lake Victoria's Pilkington Bay, subsampled at 21- to 25-year intervals and supported by 20 AMS dates, reveals a ~10,000 calendar year environmental history that is supported by published diatom and pollen data from two nearby sites. With their chronologies adjusted here to account for newly documented ancient carbon effects in the lake, these three records provide a coherent, finely resolved reconstruction of Holocene climate change in equatorial East Africa. After an insolation-induced rainfall maximum ca. 8800-8300 cal yr B.P., precipitation became more seasonal and decreased abruptly ca. 8200 and 5700 yr B.P. in apparent association with northern deglaciation events. Century-scale rainfall increases occurred ca. 8500, 7000, 5800, and 4000 yr B.P. Conditions after 2700 yr B.P. were generally similar to those of today, but major droughts occurred ca. 1200-600 yr B.P. during Europe's Medieval Warm Period.

Abstract: Who is responsible for the ongoing degradation of natural resources such as agricultural soils, rangeland, and forests? Evidence from across Latin America suggests that the nonpoor and the poor are both at fault. While the poor lack the means to invest in protecting natural resources, both the nonpoor and the poor often lack the incentives for good resource stewardship. Policies for agricultural intensification and livelihood diversification can alleviate poverty and its capacity constraint. But incentive policies for good stewardship are critically needed. Such policies should be targeted to specific environmental problems and tailored to the motivations of rural decision makers.

Abstract: Nonnative plant species are causing enormous ecological and environmental impacts from local to global scale. Remote sensing images have had mixed success in providing spatial information on land cover characteristics to land managers that increase effective management of invasions into native habitats. However, there has been limited evaluation of the use of hyperspectral data and processing techniques for mapping specific invasive species based on their spectral characteristics. This research evaluated three different methods of processing hyperspectral imagery: minimum noise fraction (MNF), continuum removal, and band ratio indices for mapping iceplant (Carpobrotus edulis) and jubata grass (Cortaderia jubata) in California's coastal habitat. Validation with field sampling data showed high mapping accuracies for all methods for identifying presence or absence of iceplant (97%), with the MNF procedure producing the highest accuracy (55%) when the classes were divided into four different densities of iceplant.

Abstract: The stable carbon isotope ratio of fossil tooth enamel carbonate is determined by the photosynthetic systems of plants at the base of the animal's foodweb. In subtropical Africa, grasses and many sedges have C4photosynthesis and transmit their characteristically enriched 13C/12C ratios (more positive [delta]13C values) along the foodchain to consumers. We report here a carbon isotope study of ten specimens of Australopithecus africanus from Member 4, Sterkfontein (ca. 2.5 to 2.0 Ma), compared with other fossil mammals from the same deposit. This is the most extensive isotopic study of an early hominin species that has been achieved so far. The results show that this hominin was intensively engaged with the savanna foodweb and that the dietary variation between individuals was more pronounced than for any other early hominin or non-human primate species on record. Suggestions that more than one species have been incuded in this taxon are not supported by the isotopic evidence. We conclude that Australopithecus africanus was highly opportunistic and adaptable in its feeding habits.

Abstract: Climate-change induced alterations in the global distribution of cool season (C3) and warm season (C4) grasses would impact the global carbon cycle and have differing, local effects on range and agricultural production. We hypothesize that a major influence on C3/C4 distribution may be the seasonal timing of water availability with respect to the different C3 and C4 growing seasons. An algorithm expressing this hypothesis (the SAW hypothesis for Seasonal Availability of Water), estimates C3 versus C4 grass biomass from climate data. Sensitivity analysis indicated that temperatures used to delineate the start and end of the C3 and C4 grass growing seasons were more important than photosynthetic responses to temperature. To evaluate the SAW hypothesis, this algorithm was applied globally on a 1°�1° latitude-longitude grid. When compared with vegetation survey data at 141 locations in North America, Argentina, Australia, and South Africa, SAW algorithm predictions yielded an R2 of 0.71. Error resulted primarily from comparing large grid cells to plot data, interannual variability of climate, and from gridding measured climate to data-sparse locations with a single lapse rate of air temperature with elevation. Application of the SAW algorithm to a climate change scenario suggested that changes in temperature and precipitation patterns could offset C3 photosynthetic advantages offered by elevated atmospheric CO2 concentrations. These results underscored the importance of accurately representing the timing and spatial distribution as well as the magnitude of temperature and precipitation in scenarios of future climate.

Abstract: This paper draws on recent empirical studies of changing land and water use in semi-arid Africa to identify socioeconomic and political dynamics and discusses their implications for current policy which emphasizes decentralization and the strengthening of "local"--often customary--land rights. The paper presents cases where local initiative in response to market opportunities is driving investment and intensification of water use to increase production. This trend is associated with an increase in individualized control and market relationships in access to land, with increasing disadvantage to the poor. It is argued that this "default" pattern of development is occurring irrespective of the formal system of land tenure and may be promoted, rather than inhibited, by policies of decentralizing natural resource management.

Abstract: Thorn removal experiments quantified the effects of plant spinescence on the foraging efficiency of two mammalian browsers of similar body size, the indigenous bushbuck and the introduced domestic boergoat. Spinescence limited the intake rates of both browsers; the extent being influenced by the animal's feeding technique. Larger bite sizes and rates enabled the bushbuck to increase their intake rate from dethorned branches. Spinescence restricted the feeding style of boergoats. Following thorn removal they attained larger bite sizes, and therefore greater intake rates. Boergoats were intrinsically fast eaters and were more efficient than bushbuck when foraging on spinescent species.

Abstract: Transformation of natural vegetation to other land-uses, such as crop cultivation and urban development, presents the most important threat to biodiversity. Plant and animal species distribution data were employed to identify areas of high biodiversity value in the major summer crop production region in north-eastern South Africa. These areas of biodiversity conservation importance were then evaluated in terms of their (1) potential overlap with areas currently transformed by land-uses in the region and (2) potential co-occurrence with areas of natural vegetation cover likely to become cultivated. Integrating species distribution, land-cover and land capability data allowed for potential conflict areas, i.e. areas with a high biodiversity value facing large current or future land transformation threats to be identified. Areas of potential conflict appear to be central Gauteng, the KwaZulu-Natal coastline, Maputuland and the escarpment of Mpumalanga. Most of the arable areas, that are not currently under some form of land-use, are marginal lands where the physical land characteristics demand high input costs, give rise to low yields and are thus not suitable for full scale commercial cultivation. As the results indicate some of these areas have a high biodiversity value, land reform programs should therefore refrain from promoting cultivation on marginal lands in these conflict areas, as they provide the last safe havens for many species. The proportion of bird, butterfly, mammal and plant species' ranges remaining in an untransformed state was quantified. Animal species with less than 60% of their natural range remaining, referred to as impacted species, comprised 63 bird, 207 butterfly and 15 mammal species. The grid cells containing these impacted species were identified as additional potential conflict areas. This study presents evidence that there is significant overlap between areas of biodiversity conservation interest and transformed or arable land in this region of South Africa and that there is an urgent need for the formulation of appropriate policies to promote biodiversity conservation on private farmland.

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Abstract: The age-constrained pollen data of a sedimentary sequence from the crater Lake Masoko, southern Tanzania (9°20'S, 33°45'E, 770 m), display a continuous record of vegetation for the past 4200 years. This record provides evidence that wetter Zambezian woodlands always occupied this area during the late Holocene, reaching a maximum extent between 2800 and 1650 cal yr BP related to increase in summer monsoon intensity. However, three main episodes of decline have been detected, between 3450 and 2800 cal yr BP, between 1650 and 1450 cal yr BP and from 1200 to 500 cal yr BP, for which a climatic interpretation, decrease in the summer monsoon strength, was preferentially advanced. The first is synchronous with lowstand of many tropical African lakes and, so, mainly induced by increased aridity. In contrast, the abrupt change in the pollen record at 1650-1550 cal yr BP is marked by a large extension of grasslands at the expense of arboreal cover, further by an increase in Ricinus communis and an intensification of burning. It could thus indicate local clearance of vegetation by man. However, at the same time, the decline of montane forest suggests the impact of a more regional change. During the last episode, between 1200 and 500 cal yr BP, dry climatic conditions are inferred from a combination of pollen, diatom and magnetic proxies, although the occurrence of Late Iron Age settlements in the region means that local human interference cannot be excluded. This study illustrates the difficulties in deciphering ecological and anthropological changes from pollen data in African tropical regions.

Abstract: Morphological and biogeochemical evidence suggest that australopithecines had diets markedly different from those of extant great apes. Stable carbon isotope analysis, for example, has shown that significant amounts of the carbon consumed by australopithecines were derived from C4 photosynthesis in plants. This means that australopithecines were eating large quantities of C4 plants such as tropical grasses and sedges, or were eating animals that were themselves eating C4 plants. In contrast, there is no evidence that modern apes consume appreciable amounts of any of these foods, even in the most arid extents of their ranges where these foods are most prevalent. Environmental reconstructions of early australopithecine environments overlap with modern chimpanzee habitats. This, in conjunction with the stable isotope evidence, suggests that australopithecines and great apes, even in similar environments, would utilize available resources differently. Thus, the desire or capacity to use C4 foods may be a basal character of our lineage. We do not know, however, which of the nutritionally disparate C4 foods were utilized by hominids. Here we discuss which C4 resources were most likely consumed by australopithecines, as well as the potential nutritional, physiological, and social consequences of eating these foods.

Abstract: The response of bird communities to a gradient of agricultural intensity was investigated in Burkina Faso, West Africa. Such knowledge may aid in predicting how avian diversity copes with increased human population density and land-use. A total of 34 transects were established on which bird censuses were made to test the effects of different fallow age, soil type and grazing intensity. Avian species richness was highest on actively disturbed land and gradually decreased with time since disturbance. Of 23 species restricted to one land-use type, 16 were found on cultivated land or recent fallows, 8 of them being categorized as uncommon in West Africa. Guild analyses suggest that availability of nest sites and food were the principal factors affecting bird distribution. For birds to persist in the agricultural landscape woody vegetation should include many different species and large trees should occur in the fields. Cultivated lands on the cuirasse had the highest average number of birds and many species were restricted to this land-use type. The potential for negative impact on the bird community was hence particularly high on the cuirasse.

Abstract: We contend diets and habitats that allow animals to select among alternatives enable individuals to better meet needs for nutrients and to better cope with toxins. All plants contain toxins, and the amount of toxin an animal can ingest depends on the kinds and amounts of nutrients and toxins in the forages on offer. Nutrients and toxins both cause animals to satiate, and excesses of nutrients, nutrient imbalances, and toxins all limit food intake. Thus, individuals can better meet their needs for nutrients and regulate their intake of toxins when offered a variety of foods that differ in nutrients and toxins than when constrained to a single food, even if the food is "nutritionally balanced". Food intake and preference also depend on differences in how individual animals are built morphologically and how they function physiologically, and marked variation is common even among closely related animals in needs for nutrients and abilities to cope with toxins. Transient food aversions compound the inefficiency of single-food diets--whether in confinement, on pastures, or on rangelands--by depressing intake among individual animals, even if they are suited "on average" to that nutrient or toxin profile. Thus, feeding and grazing practices that allow producers to capitalize on the individuality of animals are likely to improve performance of the herd by enabling the uniqueness of individuals to become manifest. Finally, past experiences play a crucial role in an animal's propensity to learn to eat different foods. When herbivores are allowed to eat only the most preferred plants, they are not likely to learn to mix foods high in nutrients with foods that contain toxins. Conversely, herbivores encouraged to eat all plants in an area are more likely to learn to eat mixes of plants that mitigate toxicity. Experienced animals who have learned to eat a variety of foods that differ in nutrients and toxins do so even when nutritious alternatives are available, whereas naive animals familiar only with the nutritious alternatives eat only that subset of familiar foods. Different systems of management alter how animals forage. Continuous grazing at low stock densities encourages selectivity and reduces diet and habitat breadth, whereas short-duration grazing at high stock densities increases diet and habitat breadth. Thus, what was traditionally considered proper grazing management--rotational grazing at low stock densities--may have trained generations of livestock to "eat the best and leave the rest" thus inadvertently accelerating a decline in biodiversity and an increase in the abundance of less desirable plant species.

Abstract: This paper examines variation in local perceptions of risk in semi-arid Tanzania, identifying factors that influence local perceptions of problems and testing the feasibility of risk mapping as a technique. Twelve villages in six districts were visited between February and April 2001. Villagers were asked about their worries and concerns in providing for themselves and their families using a risk questionnaire. The responses were grouped into 21 categories of problem and incidence and severity indices were calculated for each category. Most problems were associated with the availability of natural resources on which livelihoods depend but others related to human and social capital assets. In addition to environmental factors, livelihood strategy and gender both influenced people's perceptions of risk. Problems of irrigation and weather, for example, were important for agricultural communities while problems relating to livestock diseases, access to land and hunger were more important in pastoral communities. The risks cited by men and women generally reflected their traditional roles in society. Very broadly, the risks associated with natural capital tended to be seen as higher by men while women mentioned more problems relating to human and social capital. However, this was not always the case. Problems linked to finance, traditionally the concern of men, were ranked similarly by men and women. In projects designed to facilitate community management and control over common pool resources, the identification of common interests is particularly important. Risk mapping can provide a cost-effective way of gaining insights to help improve research design and to inform policy development.

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Abstract: Assessing the impacts of climatic and, in particular, land use changes on rates of soil erosion by water is the objective of many national and international research projects. However, over the last decades, most research dealing with soil erosion by water has concentrated on sheet (interrill) and rill erosion processes operating at the (runoff) plot scale. Relatively few studies have been conducted on gully erosion operating at larger spatial scales. Recent studies indicate that (1) gully erosion represents an important sediment source in a range of environments and (2) gullies are effective links for transferring runoff and sediment from uplands to valley bottoms and permanent channels where they aggravate off site effects of water erosion. In other words, once gullies develop, they increase the connectivity in the landscape. Many cases of damage (sediment and chemical) to watercourses and properties by runoff from agricultural land relate to (ephemeral) gullying. Consequently, there is a need for monitoring, experimental and modelling studies of gully erosion as a basis for predicting the effects of environmental change (climatic and land use changes) on gully erosion rates. In this respect, various research questions can be identified. The most important ones are: What is the contribution of gully erosion to overall soil loss and sediment production at various temporal and spatial scales and under different climatic and land use conditions? What are appropriate measuring techniques for monitoring and experimental studies of the initiation and development of various gully types at various temporal and spatial scales? Can we identify critical thresholds for the initiation, development and infilling of gullies in different environments in terms of flow hydraulics, rain, topography, soils and land use? How does gully erosion interact with hydrological processes as well as with other soil degradation processes? What are appropriate models of gully erosion, capable of predicting (a) erosion rates at various temporal and spatial scales and (b) the impact of gully development on hydrology, sediment yield and landscape evolution? What are efficient gully prevention and gully control measures? What can be learned from failures and successes of gully erosion control programmes? These questions need to be answered first if we want to improve our insights into the impacts of environmental change on gully erosion. This paper highlights some of these issues by reviewing recent examples taken from various environments.

Abstract: Abstract Fire is a key ecological process in several biomes worldwide. Although many conservation agencies have the protection of biodiversity as at least one of their major goals, information on the effects of fire on fauna in these biomes is fragmentary. Here we provide an overview of the published research undertaken to date on the effects of fire on fauna using examples from Southern Africa. We found that few studies have examined the effects of fire on amphibians or reptiles, and work on invertebrates is likewise sparse. The majority of studies that have been published are observational reports, and few experimental studies have been undertaken using an experimental fire regime, or over appropriately long time intervals. Replication was often not reported and where this was done, it was generally inadequate. The majority of the studies failed to report the area over which the studies were undertaken and sampling unit size was often not reported. Despite the importance of fire duration, ignition method, season and time of day of fire, few studies investigated these variables. We conclude that at present the information on the effects of fire on fauna in Southern Africa is fragmentary and, consequently, informed management decisions regarding the consequences of burning policies on the conservation of biodiversity both within and outside protected areas are problematic. We recommend that future studies, both in Southern Africa and elsewhere, be based on a suite of large-scale and experimental approaches (the latter firmly grounded in the principles of sound experimental design), use non-classical statistics to explore the effects of large-scale or unreplicated fires, and where possible include baseline information such as that gathered in fragmentation experiments.

Abstract: Based on the knowledge that alpaca (Lama pacos) have a lower fractional outflow rate of feed particles (particulate FOR) from their forestomach than sheep (San Martin 1987), the current study measured methane (CH4) production and other digestion parameters in these species in three successive experiments (1, 2 and 3): Experiment 1, lucerne hay fed indoors; Experiment 2, grazed on perennial ryegrass/white clover pasture (PRG/WC); and Experiment 3, grazed on birdsfoot trefoil (Lotus corniculatus) pasture (Lotus). Six male alpaca and six castrated Romney sheep were simultaneously and successively fed on the forages either ad libitum or at generous herbage allowances (grazing). CH4 production (g/day) (using the sulphur hexafluoride tracer technique), voluntary feed intake (VFI), diet quality, and protozoa counts and volatile fatty acid concentrations in samples of forestomach contents were determined. In addition, feed digestibility, energy and nitrogen (N) balances and microbial N supply from the forestomach (using purine derivatives excretion) were measured in Experiment 1.Diets selected by alpaca were of lower quality than those selected by sheep, and the voluntary gross energy intakes (GEI, MJ) per kg of liveweight0·75 were consistently lower (P0·05) in their CH4 yields (% GEI) when fed on lucerne hay (5·1 v. 4·7), but alpaca had a higher CH4 yield when fed on PRG/WC (9·4 v. 7·5, P0·05) in diet N partition or microbial N yield, but alpaca had higher (P<0·05) neutral detergent fibre digestibility (0·478 v. 0·461) and lower (P<0·01) urinary energy losses (5·2 v. 5·8 % GEI) than sheep. It is suggested that differences between these species in forestomach particulate FOR might have been the underlying physiological mechanism responsible for the differences in CH4 yield, although the between-species differences in VFI and diet quality also had a major effect on it.

Abstract: Aerial photographs are a type of remote sensing data that are especially valuable for rangeland applications. Advantages of these data include relative ease of interpretation and acquisition, affordability, high resolution (1–2 meters), and provision of a common reference for communication among those involved in rangeland management. Additionally, air photos are especially well suited for analysis of historical rangeland remediation treatments because acquisition of widespread aerial photographic coverage began during the 1930s. Several types of treatments can be easily identified and monitored over time, including contour terraces, brush water spreaders, rootplow seeding, water ponding dikes, shrub removal by grubbing, and grazing restrictions. The use of archived aerial photographs allows the opportunity to recreate the management history of rangeland, as well as to serve as a point of departure for involvement in more sophisticated satellite-based remote sensing systems.

Abstract: The rangelands of Kazakhstan were historically used for nomadic pastoralism, with long migrations to make best use of the seasonal availability of pasture. In Soviet times, livestock production was intensified. From the 1970s concerns were raised in the Soviet literature about rangeland degradation, but very little was written about Kazakhstan's rangelands in the Western literature. Rangeland science in the Soviet system uses rather different methodologies to those in the West; this needs to be taken into account when comparing the two literatures. Here we use literature reviews, fieldwork and modelling to assess the likelihood that Kazakhstan's rangelands were overgrazed in Soviet times. We conclude that the extent of degradation of the pastures in our case study areas was probably lower than suggested in the literature, but that seasonal stock movement was essential to avoid degradation. Since independence, stock numbers have collapsed and stock movements are now limited. Recent field assessments suggest that the rangelands are in good condition. Kazakhstan's rangelands present a rare opportunity for the study of rangeland dynamics under dramatically changing stock numbers.

Abstract: Semi-arid rangelands, which have retrogressed beyond a certain threshold and could not rest-recover, can only be restored by mechanical inputs helping the re-establishment of vegetation. Therefore, different over-sown species and mechanical restoration methods (hollows-dyker plough, furrows-ripper/sub-soiler and walking-stick planter) were evaluated for the restoration of bare areas on both a sandy and clayish soil type. Changes in species composition and plant density over time (1987/88-1996/97 growing seasons) were determined. The hollows with a rip action in one cultivation operation remained over a longer period and therefore caught more water for better establishment of grass species, compared with making only hollows where it silted up more easily. Establishment was poorest when only the walking-stick planter was used. Although the well establishment of Eragrostis curvula over the first 3 years, after 10 years only a few plants survived in both clay and sandy soils. Regardless of cultivation treatment or soil form, Digitaria eriantha subsp. eriantha survived the best (p<0.01) after 10 years and even spread into adjacent areas. Anthephora pubescens and Cenchrus ciliaris only established successfully in sandy soil. Restoration in semi-arid rangelands is slow and failures are common because of low and unreliable rainfall.

Abstract: Unplanned fires are a natural phenomenon in southern African rangelands. The influence of fire on soil characteristics (soil-water content, soil compaction, soil temperature, infiltration ability, soil properties especially organic matter, pH, exchangeable Ca, Mg, K, Na and extractable P) of a semi-arid rangeland was therefore quantified over two growing seasons (2000/01-2001/02) following an accidental fire. The decrease (p[less-than-or-equals, slant]0.01) in basal cover due to fire (head fires) exposed the soil more to the natural elements and therefore to higher (p[less-than-or-equals, slant]0.01) soil temperatures and soil compaction in turn leading to lower (p[less-than-or-equals, slant]0.01) soil-water content and a decline in soil infiltrability. Two growing seasons after the fire, the decrease or disturbance in soil characteristics has still not been lifted. An increase in soil temperature of as much as 9°C on top of the soil surface occurred during the first year following the fire. One growing season following the fire, the highest soil temperatures (50 mm depth) for the burnt and unburnt rangeland were 39°C and 34°C, respectively, and occurred during December. Only 4 months after the fire, the soil-water content (0-300 mm depth) was already 31% lower due to the fire and 61% lower at the end of the first growing season. Over the first 0-50 mm soil layer, fire reduced (p[greater-or-equal, slanted]0.01) organic carbon (C) and total nitrogen (N) content (as measures of organic matter content) and extractable P, but increased (p[less-than-or-equals, slant]0.01) the pH and concentration of exchangeable Ca, Mg, Na and K in the soil. With depth, organic matter and K decreased and Ca increased (p[less-than-or-equals, slant]0.01) between surface (0-50 mm) and lower (50-100 mm) layers due to burning. Accidental or unplanned fires contribute towards the so-called man-made droughts, while also influencing the short-term sustainability of the rangeland ecosystem.

Abstract: In southern African countries soil erosion and the related problems, such as water quality issues or decreasing soil productivity, are the main topics affecting the inhabitants of both rural and urban areas. Therefore, the attention has been recently placed on those problems related to soil erosion. This can also be documented by an increasing number of studies carried out on erosion and by the development and application of erosion models. Nevertheless, gully erosion phenomena have been widely neglected in erosion modelling. This is because the development of erosion models was focused on those regions with an intense agriculture typical of developed countries on the one hand, and because of the spatial and temporal heterogeneity of gully erosion processes on the other hand. This study regards the identification of gully erosion forms and processes in the Mbuluzi River catchment (Kingdom of Swaziland) by using the Erosion Response Units (ERU) concept. The following modelling of gully erosion was done through the stable gully model [Catena 37 (1999) 401]. The input data were obtained through the application of remote sensing techniques (API method) and GIS-analyses. The example from Swaziland shows that the applied methods are able to identify areas affected by gully erosion. Furthermore, it is possible to estimate the amount of soil loss due to gully erosion, which, for example, is not taken into consideration by the USLE-type models.

Abstract: That data from polar orbiting satellites have detected a widespread increase in photosynthetic activity over the last 20 years in the grasslands of the Sahel is justifies investigating its role in the tropical carbon cycle. But this task is undermined because ground data that are generally used to support the use of primary production models elsewhere are lacking. In this paper, we profile a Light Use Efficiency (LUE) model of primary production parameterised with satellite information, and test it for the West African Sahel; solar radiation is absorbed by plants to provide energy for photosynthesis, while moisture shortfalls control the efficiency of light usage. In particular, we show how an economical use of existing, yet meagre data sets can be used to circumvent nominal, yet untenable approaches for achieving this for the region. Specifically, we use a cloudiness layer provided with the NOAA/NASA 8 km Pathfinder Land data archive (PAL) data set to derive solar radiation (and other energy balance terms) required to implement the model (monthly time-step). Of particular note, we index growth efficiency via transpiration by subsuming rangeland-yield formulations into our model. This is important for partially vegetated landscapes where the fate of rainfall is controlled by relative vegetation cover. We accomplish this by using PAL-derived Normalised Difference Vegetation Index (NDVI) to partition the landscape into fractional vegetation cover. A bare soil evaporation model that feeds into bucket model is then applied, thereafter deriving actual transpiration (quasi-daily time-step). We forgo a formal validation of the model due to problems of spatial scale and data limitations. Instead, we generate maps showing model robustness via Monte Carlo simulation. The precision of our Gross Primary Production (GPP) estimates is acceptable, but falls off rapidly for the northern fringes of the Sahel. We also map the locations where errors in the driving variables are mostly responsible for the bulk of uncertainty in predicted GPP, in this case the water stress factor and the NDVI. Comparisons with an independent model of primary production, CENTURY, are relatively poor, yet favourable comparisons are made with previous primary production estimates found for the region in the literature. A spatially exhaustive evaluation of our GPP map is carried out by regressing randomly sampled observations against integrated NDVI, a method traditionally used to quantify absolute amounts of primary production. Our model can be used to quantify stocks and flows of carbon in grasslands over the recent historical period.

Abstract: This work analyzed the effects of management practices over 30 years in Orinoco savanna ultisols. The long-term effects were evaluated by comparing soil organic carbon (SOC) and total nitrogen (TN) changes, as well as carbon and nitrogen mineralization, in (1) a continuous woodland-savanna fallow (T1); (2) a perennial Brachiaria(Brachiaria decumbens Stapf.) field under intensive cattle raising (T2), which was tilled and renewed every 5 years; (3) a cowpea (Vigna unguiculata (L.) Walp.) field (T3), which was annually tilled and fallowed during the rest of the year; and (4) native savanna under extensive cattle raising (T4). Management practices (i.e. T2-T4) corresponded to the productive systems under conditions representative of normal use in the Orinoco llanos. The fallow influenced the quantity and quality (i.e. mineralizable C and N) of soil organic matter. Over 30 years, the effect of savanna fallow was to increase the SOC and TN from 2092±295 and 153±24 to 3514±300 and 310±46 g m-2, respectively. In this fallow treatment, the temporal pattern of SOC and TN changes were described by an exponential increase after 15 years of fallowing. For the grazed Brachiaria, cowpea and native grazing savanna, SOC and TN remained in equilibrium throughout the period. The soil potential N mineralization, in the woodland-savanna fallow, reached 21.4 g N m-2. In the other treatments, it ranged from 10.0 to 11.8 g N m-2. In all plots, the NH4-N/NO3-N ratio was above unity and nitrification occurred in the absence of autotrophic nitrifiers. Carbon mineralization in the woodland-savanna fallow, as expressed by field measurements of the annual heterotrophic respiration (628 g C m-2 per year), was lower than that in the other systems. However, microbial density did not differ between treatments. Over 30 years, different SOC and TN levels in the soil treatments were related to litter input production. The described sustainable use of the analyzed systems provided clues for conserving soil and maintaining system productivity in the Orinoco llanos and comparable lowlands under similar climatic and edaphic conditions. However, optimal combination of organic and inorganic fertilizers depends on both socio-economic and environmental factors.

Abstract: Carbon (13C:12C) and oxygen (18O:16O) stable isotope ratio analysis was performed on well-preserved tooth enamel carbonate from fossil fauna recovered from a single excavation at the early hominid site of Allia Bay, East Turkana, Kenya. These data show greater enrichment in both 12C and in 16O than expected, based on the oxygen isotope composition of the middle Pliocene ocean, and on today's ecology. The pattern of these data argues against a diagenetic explanation for the enrichment. The carbon stable isotope data of known browsers suggest a more extensive canopy cover during the middle Pliocene than today's environments. The presence of browsing pig genera, hippo genera, deinotheres, and giraffes with [delta]13C values more negative than today's all argue for woodland habitats. The presence of several grazing genera point to the presence of grasslands as well. The oxygen stable isotope ratios indicate that the site was better-watered than today, although the source, seasonal pattern, and actual amount of water cannot be determined from these data. The overall mosaic of environments suggested by these data, in combination with reports of exotic trees recovered in nearby deposits, indicate that woodlands were present in the region 3.9 my, unlike today. Such a setting matches expectations for the selective advantages of nut-eating, bipedal hominids over other hominoids.

Abstract: Abstract 10.1002/jqs.725.abs Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755-cm-long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon-isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold-tolerant NADP-MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd.

Abstract: Proxy environmental records have been obtained for the last 160 kyr from the well-studied ODP Site 658, ca. 200 km West of Cap Blanc, N.W. Africa (20°5'N, 18°35'W; 2263 m water depth). This collective assessment of several terrigenous proxies (lithogenic fraction, n-alkane content and [delta]13C values, and pollen counts) provides a better understanding of the climate and vegetation history of the N.W. African hinterland. The results indicate that, for this site beneath the main dust pathway of the Saharan Air Layer (SAL), the dust flux increased during dry glacial periods but the amounts of pollen and n-alkanes delivered were lower, in accord with the decreased density of vegetation cover of their source areas. The % [`]C4 pollen' was also very low, but the heavy [delta]13C values of the n-alkanes accorded with a mainly C4 plant origin. Evidently, the load of SAL-pollen was much reduced, but not the SAL wind strength.

Abstract: The hillslope erosion model (HEM) was developed to describe erosion and sediment yield on rangelands and is based on mathematical relationships among sediment yield, runoff, hillslope characteristics, and a relative soil erodibility value. It is available on the web site, http://www.eisnr.tucson.ars.ag.gov/HillslopeErosionModel. Currently, HEM has had limited application outside the USA. Our aim was to test the utility of the model with data from (a) a sandy loam at Hyderabad, India; (b) a clay loam at Pukekohe, New Zealand; and (c) a heavy red clay soil in northern Australia. Calibration showed that derived relative soil erodibility values for Indian and Australian locations differed from those determined for the USA datasets, however the default value appeared to be applicable for the New Zealand data with some variability. Our testing suggests that further calibration and analysis are necessary before default values can be identified for all sites. We also suggest however, that cautious use with derived soil erodibilities is possible at these locations, as further model testing occurs.

Abstract: This paper provides an introduction and overview for the special issue on systematic conservation planning in the species-rich and highly vulnerable Cape Floristic Region. Firstly, we outline the three major problems that created the need for a systematic conservation plan and implementation programme in the region, namely an existing reserve system that is not representative of biodiversity patterns and processes, escalating threats to biodiversity, and diminishing institutional capacity. Secondly, we present the framework used for the planning and implementation process, place the contributions to the special issue in this context, and summarise current implementation initiatives. Thirdly, we extract from these studies and our own experience a number of lessons that were learnt during the planning process. Foremost amongst these lessons is a requirement for effective incorporation of implementation issues at all stages of the planning process. Other lessons include the need to consult and involve stakeholders at the local (municipal) level, the importance of a common planning framework for all teams contributing to the plan, the importance of mainstreaming biodiversity concerns as an implementation mechanism, the requirement for a critical level of home-grown capacity for undertaking ecoregional planning, and the value of expert knowledge when incorporated into a systematic planning framework. We conclude by suggesting that the approach used in this planning process, modified by accommodating the lessons learnt, has general applicability.

Abstract: We produced a conservation plan that achieved conservation targets for biodiversity pattern and process in the species- and endemic-rich Cape Floristic Region of South Africa. Features given quantitative conservation targets were land classes, localities of Proteaceae and selected vertebrate (freshwater fish, amphibians and reptiles) species, population sizes for medium- and large-sized mammals, and six types of spatial surrogates for ecological and evolutionary processes. The plan was developed in several stages using C-Plan, a decision support system linked to a geographic information system. Accepting the existing reserve system as part of the plan, we first selected spatially fixed surrogates for biodiversity processes; then we included those planning units that were essential for achieving targets for land classes, Proteaceae and vertebrate species; next we included areas required to accommodate population and design targets for large and medium-sized mammals; we then selected planning units required to conserve entire upland-lowland and macroclimatic gradients; and finally we resolved the options for achieving remaining targets while also consolidating the design of conservation areas. The result was a system of conservation areas, requiring, in addition to the existing reserve system, 52% of the remaining extant habitat in the planning domain, as well as restorable habitat, that will promote the persistence and continued diversification of much of the region 039;s biota in the face of ongoing habitat loss and climate change. After describing the planning process, we discuss implementation priorities in relation to conservation value and vulnerability to habitat loss, as well as socio-economic, political and institutional constraints and opportunities.

Abstract: There is a growing concern in central and southern Africa about the negative effects of deforestation caused by shifting cultivation and charcoal production. In the absence of long-term studies that document and assess impacts of tropical deforestation, it is difficult to evaluate the relevance of current policy interventions that address the negative effects of deforestation. To contribute to the knowledge about impacts of tropical deforestation, the effects of clearing Brachystegia-Julbernardia (miombo) woodland on grass biomass and soil nutrient status were assessed at four sites over a 10-years period, from 1991 to 2000 in central Zambia. Woodland clearing increased grass biomass by 20-50% and although its impacts on topsoil organic matter and available phosphorus were apparent, these were not statistically significant. Site and year had the most significant effects on soil nutrient stocks, regardless of the woodland clearing treatment. Generally, fire did not affect grass production but reduced topsoil organic matter and nitrogen at three of the study sites. Deforestation followed by cultivation significantly reduced soil organic matter in the study area. Based on these results, it is recommended that local cultivation practices should incorporate measures that minimize loss of soil organic matter in order to sustain long-term soil fertility.

Abstract: Botswana 039;s Kalahari rangelands have historically supported a diversity of wildlife and a number of subsistence livelihood activities, such as agropastoralism, hunting and gathering. Recently, however, concerns about environmental and livelihood sustainability in the Kalahari have been raised. This paper demonstrates the validity of these concerns using data from research undertaken in the Matsheng area of southwest Botswana. It is illustrated that: (a) Matsheng soils are too infertile to sustain productive arable farming, (b) herbaceous vegetation cover decreases in a reversed decay function towards settlements, (c) the herbaceous vegetation cover trend is inversely reflected by woody-thorny vegetation, (d) despite being a major rangeland activity, livestock production benefits only a minority of inhabitants, and (e) rangelands are no longer the major source of livelihood for the majority.

Abstract: A recent national erosion assessment programme reveals that soil erosion is more active in Iceland than is witnessed in other European countries. Most of the communal grazing areas in the central highlands are not suitable for grazing by sheep because of poor condition. Agricultural subsidies are a substantial proportion of Iceland 039;s national budget and the sheep farming is dependent on subsidies. Recently, a landmark agreement was made between sheep farmers and the government, where part of the production subsidies were tied to 34;quality management 34;, including sustainable land use. This agreement calls for rapid assessment of all grazing land in Iceland. These challenges have been met by the use of classification of satellite imagery and innovative methods in obtaining farmland boundaries. The subsidy agreement may have more importance for attaining sustainable land use in Iceland than most government initiatives to date. Financial incentives, such as linking subsidies to land condition and improvements, encourage a reduction of grazing pressure on marginal highland areas, but do not lead to exclusion of such grazing practices. We believe that Icelandic rangelands should be divided into two categories: land intended for use (farmland), and land that should be protected from grazing by national law.

Abstract: The Drakensberg Alpine Centre (DAC) comprises the 40,000km2 high-altitude range of hills, mountain peaks and escarpment plateau bordering the eastern interior of southern Africa. Renowned for its species-rich flora and high levels of endemism, the DAC is here shown to support over 2800 specific and infraspecific native taxa, with c.16% of the angiosperm taxa being endemic, the latter equalling the flora of KwaZulu-Natal. Comparisons of the DAC 38;apos;s largest families and genera are made with those of the Cape Floral Region and KwaZulu-Natal, and the largest families are also compared with those of the Afromontane and Pondoland regions. In addition, comparisons are made between the high-altitude floras of southern and south-central Africa on the basis of their Cape element.

Abstract: Expert-based and systematic, algorithm-based approaches to identifying priority areas for conservation are sometimes posited as alternatives. While both approaches have pros and cons, the systematic approach does have the advantage of providing a region-wide assessment of the options for achieving explicit conservation targets. A distinct advantage of the expert-driven approach is its incorporation of expert knowledge on biodiversity persistence and pragmatic management and implementation issues not normally included in biodiversity feature-site data matrices. Given the widespread application of both approaches, surprisingly little research has been undertaken to evaluate their conservation planning outcomes. Here we compare priority conservation areas in South Africa 039;s Cape Floristic Region identified by park managers and reserve-selection software. Managers identified 29 areas (a wishlist) that together, comprised 31% of the planning domain and had 40% of its area under some form of conservation management. This wishlist was assessed for the extent to which it achieved targets for biodiversity pattern and process over and above the existing conservation system, and its incorporation of priority areas identified in terms of conservation value and vulnerability to processes that threaten biodiversity. Overall, the wishlist reflected a desire by managers to improve management efficiency and facilitate rapid implementation by expanding existing, largely montane reserves into low-priority areas where land tenure is sympathetic to conservation. Consequently, it was not very effective and efficient in achieving pattern and process targets, and it excluded large areas of vulnerable and inadequately conserved lowland habitat�the areas currently in most need of conservation action. Further, it provided no basis for scheduling implementation or for exploring alternative areas to achieve the same goals, unlike systematic approaches. Nonetheless, the manager 039;s wishlist did include many highly innovative and feasible projects that make important contributions to the conservation of the region 039;s biodiversity. Rather than emphasize the dichotomy between expert and systematic approaches, conservation planners should devise ways of integrating them. In particular, priority areas identified by experts should be carefully considered against the backdrop of the outcomes of systematic conservation planning.

Abstract: In many South African catchments, water is an increasingly limited and highly fluctuating resource. Accurate prediction of low flows is especially vital if water resource managers are to successfully balance the growing needs of agriculture, industry and rural and urban populations, while maintaining the ecological health of aquatic and riparian ecosystems. Existing hydrological models in use in South Africa suffer from a number of disadvantages. They are complex, over-parameterised, data demanding and expensive to use. IHACRES, a lumped conceptual model requiring minimal input data, is less limited by these problems, and has the potential to advance our understanding of streamflow patterns and predict how these may be altered by land-use change. The purpose of this paper is to evaluate IHACRES performance for two South African catchments: Lambrechtsbos A (a 31 ha research catchment) and Groot-Nylrivier (74 km2). IHACRES predicted streamflow at Lambrechtsbos A with useful accuracy (pre-afforestation period, R2 62;0.81; bias 60;26 mm/yr; post-afforestation period, R2=0.81, bias=8.4 mm/yr). With prior knowledge of changes in annual evapotranspiration, predictions of land-use impacts on flow regime may be satisfactorily predicted. Simulations of flows in the Groot-Nylrivier catchment were found to be of useful accuracy for relatively short periods of 2-3 yr, but performance over longer time periods was reduced by poor predictions in certain years. We ascribe this primarily to poor catchment-average rainfall estimation following certain storms in some years. Our simulations highlighted a tendency for IHACRES to underestimate quick flow events, especially at times when the greater part of a catchment is dry. Further model development is required to overcome these problems. IHACRES shows great potential in linking proposed land-use change to altered flow regimes, and efficiently describing the flow characteristics within catchments. However, poor estimation of average rainfall in larger catchments is a limitation that needs to be overcome before long-term flow regimes of non-research catchments may be predicted with confidence.

Abstract: The formulation of a strategic plan for the conservation of terrestrial biodiversity in the Cape Floristic Region (CFR; 87,892 km2) requires an objective and spatially explicit assessment of the representativeness of major habitat categories (surrogates for biodiversity) currently under protection. A GIS layer of statutory and non-statutory conservation areas was used, along with layers of many biological and physical features, to explore the configuration of conserved areas relative to key biological and physical indicators. Three analyses were performed. (1) Recursive partitioning, a classification-tree analysis technique, was used to contrast features of protected areas with non-protected areas. (2) The conservation status of 16 primary and 88 secondary Broad Habitat Units (BHUs; derived on the basis of topography, geology, homogeneous climatic zones, and floristic composition) was assessed in terms of prescribed conservation targets. (3) The extent to which protected areas are able to sustain ecological and evolutionary processes was explored by assessing the extent of spatial components of these processes for all conservation areas. About 20% of the CFR is protected in some form of conservation area, mostly concentrated on sandstone substrates, and areas with high altitude and steep slopes. The reservation bias towards upland areas has seriously constrained representation of biodiversity pattern and processes. Most of the habitat diversity is poorly represented in the current conservation area system with only 9% of the remaining primary BHUs in the lowlands conserved. However, almost 50% of the Mountain Fynbos Complex is conserved (largely exceeding its conservation target). Spatial components of the ecological processes identified are poorly captured by the conservation area network although faunal and floral migration is possible in the uplands due to the strong spatial connectivity of the protected network.

Abstract: Abstract Bush fires are the main cause of natural resource degradation in Niokolo Koba National Park. So-called �early fires� or management fires are considered an irreplaceable tool for land management in protected areas. A synthesis of the literature and field observation reveals that plateaus and slopes are the most prone to burning. Fire proneness depends mainly on vegetation characteristics. The main vegetation types on plateaus and slopes are shrub and arboreal savannah, respectively. These savannah types are both dominated by Combretaceae in the ligneous stratum, while in the herbaceous layer species of Poaceae family dominate. The predominance and state of Poaceae in the herbaceous layer are major indicators of fire readiness. It is sought to adopt a strategy for early fire implementation that minimizes impact on natural resources. Any strategy must include an operational system for monitoring herbaceous fuel conditions. Such a system could benefit from new remote sensing technologies when combined with field measurements in the most exposed zones.

Abstract: This study investigates the practical and financial implications of alternative strategies for meeting explicit conservation goals on the Agulhas Plain, South Africa. This is an area of exceptional biodiversity increasingly threatened by alien plant infestation, urbanisation, and agricultural expansion. In addition to traditional on-reserve protection, we identify two types of property-rights agreements (conservation easements and management agreements) and two types of financial incentives (land management assistance and tax relief) as appropriate for encouraging off-reserve conservation on targeted lands in the area. Specifically, we suggest actions to offset the costs facing landowners under new pieces of legislation, such as alien-clearing requirements and a property tax. After refining an existing GIS database of cadastral units targeted for conservation, we assigned on- or off-reserve conservation status to properties on the basis of a simple decision system, which took the irreplaceability of the area into account. Three implementation scenarios were designed: an entirely [�]on-reserve 039; approach, a mixed on- and off-reserve approach, and the mixed approach in conjunction with financial incentives. The conservation costs, to both the public and private sector (including expanded obligations from new legislation), were first modelled and then analysed in a Geographic Information System. We found that a traditional on-reserve approach would cost the state about R240M in acquisition costs, whereas both mixed approaches, using the decision rules developed in this study, would involve leaving 40% of targeted areas in private hands, saving the state 80% in acquisition costs. Of the subsequent conservation costs, which total R401M (present value @ 6% discount rate; Scenario 1), most are alien clearing costs. Since landowners are now compelled to put up these costs, the state could make further savings (44-51%) under a mixed management scenario. Using Property Rate relief as an additional financial incentive is relatively efficient in that it may save targeted private landowners 32% in Property Rates, at a cost of 5.5% of expected tax revenue to the state. Given the prohibitive costs, realising conservation goals in the Agulhas Plain will probably depend upon the establishment of institutions, mechanisms, and incentives for private participation in conservation.

Abstract: Two vibrodrill and six core drill cores were recovered in Lake Assom near Tibati, south of Adamawa. From eight radiocarbon ages on samples from the two vibrodrill cores and on the basis of sedimentological analysis, a reconstitution of the environmental history of this site for the late Holocene has been done. These results suggest the Lake Assom has remained swampy or even dry since 2800 years BP. Spectacular deposition of compact muddy intraclasts strongly suggests that this situation was suddenly interrupted close to [approximate]1700 years BP when the lake was inundated by water. This deposition can be compared to that of coarse materials observed at the base of the erosion profile 34;Basse Terrasse 34;. In spite of this present filling trend, the lacustrine state of the site seems to still pertain. Observations done on the lake banks and the occidental swampy plain, compiled with those from the well in the centre of the small adjacent depression of Ngwana, enable us to better understand the recent functioning of the lake. The Mandjara river certainly played a major role in the sedimentation of sandy gley, and later in the high energy reworking of older coarse intraclasts at [approximate]1700 years BP. Lake Assom seems to have originated from the dissolution of a more extensive iron crust covering the hole region of Mbella Assom. The presence today of two adjacent depressions is due to local morphology following changes in the lake during the dry period. On the other hand, palynologic studies show no indication of the proximity of any humid forest to this wooded savannah over the past 4500 years BP.

Abstract: The lack of realistic estimates of the costs of protected area establishment and effective management can hinder conservation planning and result in under-funded 34;paper parks 34; that fail to meet conservation goals. This study comprises the first comprehensive and systematic estimate of the costs of conserving a globally recognised biodiversity hotspot, the Cape Floristic Region. To our knowledge, it is also the first study to use specific relationships between protected area attributes and management costs to estimate the long-term costs of implementing a regional conservation plan. We derived a configuration for an expanded protected area system and two off-reserve mechanisms (contractual reserves and other incentive mechanisms) that achieve explicit conservation targets for biodiversity pattern and process identified in a systematic conservation planning process. Using a costing model, we then estimated the costs of establishing and maintaining this reserve system. Although the reserve system is one of many potential configurations that may achieve the designated conservation targets, the results indicate that the costs of conservation are substantial. An expenditure of $45.6 million per year, assuming a 20-year implementation horizon, is required to develop a representative reserve system, while the annual costs of maintaining this system are $24.4 million. Owing to the economies of scale, especially the marked increase in unit management costs when protected area size 60;600 ha, the predicted cost of managing the expanded system was only 1.2 times that of the existing system. Overall, the level of expenditure required to effectively conserve the region 039;s biodiversity is low relative to its regional and global significance.

Abstract: Data from stalagmites in the Makapansgat Valley, South Africa, document regional climatic change in southern Africa in the Late Pleistocene and Holocene. A new TIMS U-series dated stalagmite indicates speleothem growth from 24.4 to 12.7 160;ka and from 10.2 to 0 160;ka, interrupted by a 2.5 160;ka hiatus. High-resolution oxygen and carbon stable isotope data suggest that postglacial warming was first initiated 17 160;ka, was interrupted by cooling, probably associated with the Antarctic Cold Reversal, and was followed by strong warming after 13.5 160;ka. The Early Holocene experienced warm, evaporative conditions with fewer C4 grasses. Cooling is evident from 6 to 2.5 160;ka, followed by warming between 1.5 and 2.5 160;ka and briefly at AD 1200. Maximum Holocene cooling occurred at AD 1700. The new stalagmite largely confirms results from shorter Holocene stalagmites reported earlier. The strongest variability superimposed on more general trends has a quasi-periodicity between 2.5 and 4.0 160;ka. Also present are weaker 1.0 160;ka and 100-year oscillations, the latter probably solar induced. Given similarities to the Antarctic records, the proximate driving force producing millennial- and centennial-scale changes in the Makapansgat record is postulated to be atmospheric circulation changes associated with change in the Southern Hemisphere circumpolar westerly wind vortex.

Abstract: Cyanobacterial soil crusts may be important in arid and semi-arid ecosystems because of their ability to fix atmospheric nitrogen (N2). These crusts are very sensitive to trampling by animals, and their destruction can decrease ecosystem N inputs, affecting the productivity of the region. The objective of this study was to quantify the nitrogen-fixing activity in soil crusts during the wet season in southern African ecosystems using in situ acetylene reduction assays. The average acetylene reduction rates for each site ranged from 88 to 535 nmol m-2 h-1, were highly variable, and were lower than previously reported for other arid areas. All soil samples showed acetylene reduction activity; however, soils with crusts supported higher rates than did 34;non-crusty 34; soils under litter, moss, or sand. High values of 15N natural abundance ([delta]15N) indicated that processes other than N fixation were more important in the crusts than N fixation. For example, coupled nitrification/denitrification and ammonia volatilization or atmospheric deposition of 15N-enriched nitrate or ammonium may have caused shifts in [delta]15N within the soil crusts. The estimated annual N fixation rates ranged from 8 to 44 g N ha-1 year-1, orders of magnitude lower than values estimated in other studies. The anomalous wet conditions experienced during the year of the study may have increased the temporal availability of soil mineral N and decreased N fixation rates. However, the presence of N fixation activity in all crusts analysed and their ability to survive at high temperature and after long dry periods may provide ecosystem resilience, facilitating ecosystem recovery after severe droughts.

Abstract: The paper analyses land use trajectories in savannah woodlands in the Central-West Region, Burkina Faso and the Upper East Region in northern Ghana by use of satellite images and historical archives. Observed trends differ in terms of spatial location and correlation with population pressure from normally accepted characterizations. Colonial forestry policies are proposed as key determinants of present-day land use patterns. However, these reinforced pre-colonial land use patterns inasmuch as land gazetted as forest reserves were tracts affected by vectors of human and livestock disease. It is suggested that the transformation of wooded agricultural landscapes in the Sudano-Sahelian region is the outcome of historically and culturally embedded interactions between complex social, economic and ecological processes which operate at widely varying scales and which change over time; the implications hereof for modelling of global environmental issues is discussed.

Abstract: Although manufacturing determines mostly the current performance of companies, few companies deal systematically with the issues related to strategic capacity management. Besides decisions on outsourcing and acquisition of resources, this involves triggering process innovation, process development and improving performance by adapting organisational structures. Action research in companies reveals the importance of capacity management at a strategic level as well as the implementation at tactical and operational levels. The methods as proposed in this paper provide industrial companies with tools for implementing their manufacturing strategy. Through matching product configurations with product-market strategies and product development, they point to areas of improvement by deploying performance evaluations and the determination of performance requirements. These improvements lead to decisions on investments for resources, resource utilisation and development of processes, including initiation of manufacturing technologies.

Abstract: Although manufacturing determines mostly the current performance of companies, few companies deal systematically with the issues related to strategic capacity management. Besides decisions on outsourcing and acquisition of resources, this involves triggering process innovation, process development and improving performance by adapting organisational structures. Action research in companies reveals the importance of capacity management at a strategic level as well as the implementation at tactical and operational levels. The methods as proposed in this paper provide industrial companies with tools for implementing their manufacturing strategy. Through matching product configurations with product-market strategies and product development, they point to areas of improvement by deploying performance evaluations and the determination of performance requirements. These improvements lead to decisions on investments for resources, resource utilisation and development of processes, including initiation of manufacturing technologies.

Abstract: Policy-related research in general, and impact assessments in particular, are too loosely connected to decision-making processes. The result is often sub-optimal or even undesirable, as one of two situations arises: (1) much research is done; however, those with the real power to make decisions do not make use of all of the resulting information, or (2) advocates of contrary opinions struggle with each other, using policy-related research as ammunition. To avoid these unwanted situations, the connection between the world of knowledge and the world of decision-making should be carefully constructed, by connecting the process of decision-making to the academic research and carefully developing research goals in response to the demands of decision-makers. By making these connections in a stepwise manner, knowledge may generate new insights and views for involved decision-makers and stakeholders, thus changing perceptions and problem definitions. In this way, these actors learn about the possibilities of several alternatives as well as each other's perceptions, and thus can make educated decisions leading to the most desirable and socially acceptable solution. The way this proposed method works is illustrated using two cases in The Netherlands: the project "Mainport Rotterdam" (the enlargement of the port of Rotterdam), the project "A fifth runway for Amsterdam Airport (Schiphol)".

Abstract: In this volume in honour of John Rogers we propose a new way of looking at Gondwana and we urge our colleagues everywhere to join us in this venture. The Gondwana Alive Corridors provide a way of celebrating the unique geological, biological and cultural heritage of the Gondwana continents, and they offer a focus for the holistic management of that heritage. Here we explore a set of 15 prototype corridors from around Gondwana which together weave a tapestry of our prodigiously diverse planet. This Earth-history tapestry traces geological time from the oldest crust to the youngest ice sheets and from the earliest known life to the current activities of our human family. The corridors, in proliferating number, offer a science-based strategy towards stemming the Sixth Extinction.

Abstract: Bush fire is a widespread and recurrent feature of the African dry savannas and contributes largely to changes in the composition of vegetation communities. However, the impact on seed regeneration in local species has received little attention. This study evaluates the effects of managed bush fire on seed viability and germination capacity for 10 species of West African acacia (sensu lato), taking into consideration fire intensity (related to the quantity of combustible biomass) and seed location (in, on or above the soil) at the time of the fire. The results indicate that the behavior of different species is related to their taxonomic position. Acacia species belonging to the sub-genus Aculeiferum are characterized by their lack of integument inhibition. The consequences of the passage of fire, depending on the intensity of heat shock, are limited to seed survival: they either retain viability or die. Seeds from the sub-genera Acacia and Faidherbia albida have a hard integument that needs to be scarified in order for germination to ensue. In our study, we show that on the whole, heat shocks cannot scarify the integument of the seeds without resultant lethal damage to their embryos. This is true regardless of seed status (naked or protected by seed pods), seed location (in, on or under the soil) and fire intensity. The only species to manifest an improvement in germination capacity, under certain selective experimental fire conditions, and in relation to the non-scarified control are A. raddiana, A. seyal and A. sieberiana. Nevertheless, germination remains substantially inferior to that obtained after scarification by removal of a small piece of integument. It thus seems conceivable to conclude that, contrary to what takes place in Mediterranean climate ecosystems and the wet tropics, fire does not encourage the in situ germination of different Acacia species. This finding implies that in dry savanna areas, it is not possible to regard fire as an accessory to reforestation or natural regeneration of these species.

Abstract: This is a keynote paper focusing on regional perspectives on agriculture and biodiversity by exploring the situation in Northern Africa, the West African Sahel, East Africa and the Horn, and Southern Africa. The paper establishes that in all these regions agriculture accelerates loss of biodiversity because of attempts by farmers to increase crop and animal production to feed the increasing population and contribute to the growth of the national economies. Harmful agricultural practices, such as overcultivation, overgrazing, bush fires, cultivation of marginal and easily eroded land, mechanization and the widespread use of chemicals and pesticides, have intensified the degradation of the soil and vegetation and led to rapid decline of species types and their numbers. Agriculture and biodiversity can be complementary activities. If properly managed, agriculture should enhance and not be the enemy of biodiversity in the drylands of Africa. There is need to assess the agricultural potential of the semi-arid environments and develop specific agricultural policies or programmes to enhance their sustainable utilization and conservation of biodiversity. Information contained in this paper was gathered from the existing literature

Abstract: We constructed a simple simulation model (SESS) of the dynamics of forage growth and standing crop and cattle production to evaluate the ecological sustainability of management alternatives for extensive cow-calf production systems in northeastern México and south Texas. Equations were written to estimate annual net primary production based on range condition, annual precipitation, and soil characteristics typical of the region. Simulations were conducted for annual precipitation levels of 300, 500, and 700 mm to estimate total and green standing crop dynamics, cattle grazing efficiency, and range condition trend for different stocking rates. The model-estimated stocking rates to achieve stable or slight improvement of range condition for the three precipitation levels were close to 58, 15, and 6 ha per animal-unit-year (AUY), respectively. With the model parameterized for precipitation and soil characteristics combined with the stocking rates recommended by COTECOCA (1979. Coahuila. Tipos de vegetación, sitos de productividad forrajera y coeficientes de agostadero. Secretaria de Recursos Hidráulicos. Comisión Técnico Consultiva para la Determinación Regional de los Coeficientes de Agostadero. México), we conducted 20-year simulations for three groups of range sites of Coahuila, México (annual precipitation: 1: 270 mm, 2: 351 mm and 3: 467 mm). The trends of body condition score and range condition for years 5, 10, 15, and 20 were similar within each of the three groups. The stocking rates recommended by COTECOCA were too high for sustainability on range site groups with 270 and 351 mm annual precipitation. The simulated probabilities for pregnancy rates at different stocking rates for the three groups indicated that the stocking rates recommended by COTECOCA were too high to achieve pregnancy rates [greater-or-equal, slanted]80% in 8 out of 10 years with no supplement in the form of hay or concentrated feeds. Model simulations suggested that, in the absence of supplemental feed, ecological sustainability and acceptable livestock production could be achieved simultaneously at light stocking rates.

Abstract: The participation of local people in projects involving secondary forest resource use in developing countries is examined. Methods and approaches used by research and community development workers for collecting information are revisited. However, the focus is on people-centred methods and approaches relevant for optimising the participation of local people. A case study on secondary forest resource use in rural South Africa is presented. The sustainable use and management of forest resources demand a comprehensive knowledge about the status of the resources through participatory inventory approaches. A hypothesis is tested that the hierarchy of methods and approaches carried out at the household level generate more robust results than communal level approaches for evaluating the availability of secondary forest resources to rural households. Socio-economic factors, institutional arrangements and naturally occurring processes are noted to drive the use of forest resources. The human centred driving forces are better understood through encompassing techniques that capture the knowledge and skill of local people. Such an initiative fulfils the society-nature relationship in the context of the new sustainability science, with challenges that need to be faced with methodological innovations. One of such is the hierarchical valuation scheme that provides the rigour, the confidence and the robustness for assessing and evaluating local resource use as compared to the use of other participatory approaches at communal gatherings. Traditionally, forestry and ecological techniques are used for resource assessments and the prediction of forest resource use. The techniques often neglect local participation, and where local people were integrated, they often provided cheap labour. Traditional ecological inventory techniques are in recent times complemented with methods from social science and development disciplines through participatory learning and action. Participatory rural appraisal is the most commonly used but with its inherent flaw. The importance and use of participatory rural appraisal have been explored and found not to be as robust as previously thought. However, in order to make local participation more liberating and empowering, most weaknesses of participatory rural appraisal have been addressed by the hierarchical valuation scheme. The use of the proposed scheme is explained as a complementary technique for PRA processes, and not providing replacement for any technique.

Abstract: Nguni goats and Boer goats, which are farmed together in the savannas of the Eastern Cape Province, depend on the same feed resources. The feeding height intake rates and preferences of one of their most preferred browse species, Grewia occidentalis L. (Tiliaceae), were studied in order to indirectly determine resource partitioning between these goat breeds on the basis of feeding height. The two hypotheses tested were that taller Boer goats feed at higher levels than do Nguni goats and that both breeds have feeding height preferences that are related to differences in intake rates. Four individuals of each breed were fed branches attached to a height foraging board. The two breeds showed no particular height preference in either season. Bite rates varied with feeding height, while bite sizes and intake rates increased with feeding height. Boer goats had lower bite rates compared to Nguni goats, although both breeds achieved similar bite sizes and intake rates. Bites sizes and intake rates for both breeds were higher in summer than in winter, possibly because more browse biomass was available per branch in summer than in winter since G. occidentalis is deciduous. There was no evidence to support that feeding height preference was related to differences in intake rates. It is concluded that Boer goats may compete for forage resources during times of resource limitation. Thus, Nguni goats might be a more favourable breed in semi-arid savannas because of their smaller body-size and, therefore, absolute nutrient requirements as well as their better reproductive performance compared to Boer goats.

Abstract: A distributed GIS-based hydrological model is developed using GIS and computational hydrology techniques. The model is based on water balance consideration of the surface and subsurface processes. The surface water balance processes include precipitation infiltration, overland runoff, evapo-transpiration and canopy surface interception losses on daily time steps; The subsurface process considers soil moisture accounting on a monthly basis. The model was used to estimate generated runoff from matrix of specific geo-referenced grids representing Southern Africa. All regional and seasonal dispensation of water balances have been based on standard GIS formats for storage, spatial display and interpretation of results. Considering the 1961-1990 climatic period, we have mapped the regional variation of the mean annual soil moisture (SM), actual evapo-transpiration (AET), and generated runoff (ROF) across Southern Africa or known as the SADC region. The model estimates the mean SM of the region to be about 148 mm/year. There is a wide spatial range in the distribution of SM over the region due to the fact that the absolute soil moisture is dependent on the water retention properties of the soils considered across the region. The model prediction of the mean annual AET in the region reaches a maximum of 1500 mm, with mean 420 mm. The mean annual generated runoff from the land catchment in the region is about 151 mm/year although there is a significant inter-regional variation among the SADC countries, which is a function of the variation in the vegetation cover, soil and climate variation. Lower runoff regimes are dominant in arid areas in Botswana, Namibia and south-western part of the Republic of South Africa. Higher runoff regimes are the Northern and Western Tanzania, along the east coastal portions of Mozambique, central Mozambique, western Zambia and Malawi.

Abstract: Although goats are common domestic browsers in African savannas, factors that affect their diet selection and food intake rate are poorly understood. This study used a cafeteria-style experimental procedure to investigate the effects of season and breed on browse species intake rates and browse species preference by Boer and Nguni goats in the False Thornveld of the Eastern Cape. Six browse species that commonly occur in the study area were used: Grewia occidentalis L. (Tiliaceae), Scutia myrtina (Burm. f.) Kurz (Rhamnaceae), Diospyros lycioides Desf. subsp. lycioides (Ebenaceae), Rhus longispina Eckl. and Zeyh. (Anacardiaceae), Ehretia rigida (Thunb.) Druce (Boraginaceae) and Acacia karroo Hayne (Fabaceae=Leguminosae). Cut branches were offered to goats during winter and summer and instantaneous intake rates and preferences were measured. There were no significant differences between Boer goats and Nguni goats in dry matter intake rates per unit metabolic body weight and in preferences of the six browse species, suggesting a potential for competition should the resources become limiting. However, the intake rates of Nguni goats increased by 50% from winter to summer, while intake rates of Boer goats increased by 87%. The mean intake rate was 69% higher in summer than in winter. Intake rates varied among all browse species, except A. karroo and R. longispina. Intake rates of D. lycioides, G. occidentalis and S. myrtina were higher than those of the other three species. Intake rates tended to increase more among deciduous species than evergreen species in summer, but the effect was not consistent. Likewise, intake rate within seasons was not consistently related to leaf phenology; intake rate of deciduous species was neither lower nor higher than that of evergreen species at any time. However, the increased intake rate in summer was consistent among those deciduous and evergreen species that produce all their new leaves on new long shoots, as opposed to species that produce their new leaves on old short shoots. The consequence of the two shoot morphologies for the browsing animal is that browseable material in the former group consists of shoots and leaves, but in the latter group consists mostly of leaves only. G. occidentalis and S. myrtina were the two most preferred species. Deciduous species were not consistently more preferred than evergreen. In accordance with optimal foraging theory, nutrient intake rates consistently explained preference in winter and summer. Species that offered the highest rates of nutrient intake were most preferred.

Abstract: The distribution of pollen in marine sediments is used to reconstruct pathways of terrigenous input to the oceans and provides a record of vegetation change on adjacent continents. The wind transport routes of aeolian pollen is comprehensively illustrated by clusters of trajectories. Isobaric, 4-day backward trajectories are calculated using the modelled wind-field of ECHAM3, and are clustered on a seasonal basis to estimate the main pathways of aeolian particles to sites of marine cores in the south-eastern Atlantic. Trajectories and clusters based on the modelled wind-field of the Last Glacial Maximum hardly differ from those of the present-day. Trajectory clusters show three regional, and two seasonal patterns, determining the pathways of aeolian pollen transport into the south-eastern Atlantic ocean. Mainly, transport out of the continent occurs during austral fall and winter, when easterly and south-easterly winds prevail. South of 25°S, winds blow mostly from the west and southwest, and aeolian terrestrial input is very low. Generally, a good latitudinal correspondence exists between the distribution patterns of pollen in marine surface sediments and the occurrence of the source plants on the adjacent continent. The northern Angola Basin receives pollen and spores from the Congolian and Zambezian forests mainly through river discharge. The Zambezian vegetation zone is the main source area for wind-blown pollen in sediments of the Angola Basin, while the semi-desert and desert areas are the main sources for pollen in sediments of the Walvis Basin and on the Walvis Ridge. A transect of six marine pollen records along the south-western African coast indicates considerable changes in the vegetation of southern Africa between glacial and interglacial periods. Important changes in the vegetation are the decline of forests in equatorial Africa and the north of southern Africa and a northward shift of winter rain vegetation along the western escarpment.

Abstract: The monetary value of natural resources used by rural communities for subsistence is important when addressing issues affecting the livelihoods of impoverished rural households. There is therefore the need to attribute monetary values to non-marketed products from smallholder production systems in order to reliably account for resource availability and usage to further sound policy decisions. The objective of this paper is to present an empirical analysis of the direct-use and traded values of crop production by households, and to discuss the implications for policy development. The study was undertaken in combination with an evaluation of other livelihood sectors in Thorndale, a semi-arid rural village in the Limpopo province of South Africa. The net direct-use value of crops was estimated at $443.4 per household per annum across the village. Maize (Zea mays), watermelon (Citrullus, vulgaris), peanuts (Arachis hypogaea) and common beans (Phaseolus vulgaris) contributed over 90% to the total direct-use value of crops. Maize alone contributed 40% of this value per household at an estimated $652/ha. Marketing of resources was not a common practice, limited to only maize and peanuts. Farming was basically a rain-fed-mixed cropping system with low production inputs. Farmer support services, human capital development and tenure security were major areas identified for policy development.

Abstract: The estimated number of tsessebes on a cattle and wildlife ranch in Zimbabwe decreased during 1995-1999 from 2209 to 435 animals. Existing records of rainfall, cattle management, wildlife numbers, captures, hunting and predation were analysed and, together with a demographic model and limited fieldwork, used to identify the probable cause of this decline. There was no convincing evidence that cheetah predation, excessive legal or illegal offtakes, a food shortage as a direct consequence of the 1994/1995 drought, or interspecific competition with wild herbivores were likely causes. After the 1991/1992 drought, tsessebe number was negatively correlated with cattle biomass, suggesting that cattle and tsessebe have competed for food since then. Two factors probably caused a long-lasting reduction in the dry-season availability of green grass leaf (the preferred food of tsessebe). First, drought and heavy grazing pressure by cattle may have shifted sward composition away from leafy grasses and towards grass species with small, wiry leaves. Secondly, while shrub encroachment has been occurring for decades, the 1991/1992 drought probably encouraged the establishment of another cohort of bushes, which now compete with grasses for soil moisture, reducing the water available for grass growth during the dry season. The competition between tsessebe and cattle was masked by significant cattle destocking during 1992-1995, but became apparent after 1995 when cattle numbers were increased. This competition was exaggerated by a general decline, since 1994, in rainfall during September-October, which further reduced the late dry season supply of green grass.

Abstract: Rangelands, generally located on steep semi-arid zones, have a special importance in resource management. Continued overgrazing and erosion cause range degradation by altering plant communities and soil properties. The objective of this study was to determine changes in vegetation and soil properties along a slope on overgrazed and moderately eroded rangelands. Four study sites with three landscape positions: summit, backslope and footslope, were selected. In each position, botanical composition, canopy coverage, rangeland quality degree, and some important surface soil properties such as texture, bulk density, moisture content, organic matter content, CaCO3 content and plant available-P content, were determined. The frequency of grasses in botanical composition varied from 39.5% to 84.0%, and on the average, the frequency was lowest at summit and highest at footslope positions. The frequency of legumes at summit positions was lower than those of the other positions in two range sites. The amount of canopy coverage changed between 19.6% and 45.2%. The highest amounts were obtained in footslopes and the lowest amounts were in summits. The degree of range quality varied between 3.2 and 5.5. Based on the overall means of the four sites, there were no significant differences among the positions regarding range quality degree, but it was generally lowest at summit positions. Clay content of surface samples was lowest at backslopes in all sites. But, there were no significant differences in clay contents of the summit and footslope positions. Changes in soil bulk density showed a significant trend along the slopes, and it was generally higher in backslope and footslope than that of summit position. Soil moisture content at time of sampling and organic matter content was generally higher at footslope positions than those of backslope and summit. While the amount of plant available-P was the lowest at backslope positions of the range sites, CaCO3 content of soil was lowest at footslopes in all sites.

Abstract: Agriculture in Niger is a complex and challenging operation. Farmers are faced with low-fertility sandy soils, variable rainfall, changing social and political situations and an unfavourable economic environment. Concerns about sustaining soil fertility have been voiced by agricultural scientists, who view agriculture as the maintenance of soil nutrient capital. Many of the biological and economic attributes of these farming systems have been documented, and are becoming better understood through the growing body of agroecological literature. Although agroecology recognises social, political and cultural interactions, much less is known about the specific details of farmers' physical and biological knowledge and how this knowledge is used to make management decisions. Research in Fandou Béri village identified a local ethnopedological framework that had fundamental differences from scientific systems. Farmers' defined soils according to location, potential for production and interaction with the wider ecological framework. They drew on varied ecological knowledge and experiences to make complex and dynamic farm decisions, as at other Sahelian villages. Local soil fertility management depends on individuals' capabilities, perceptions of constraints and opportunities, and their ability to mediate access to different types of resources. This research suggests that there is a need to maximise the benefits of indigenous knowledge by integrating social and natural science, for example to help [`]precision farming', and to use it to understand diversity.

Abstract: This paper provides an analysis of the ecological ideas which underpin policies of elephant management and ivory trading in African elephant range states. Increasingly, the discussion surrounding the international trade in ivory has focussed on potential revenue that could be generated from the sale of stock-piled ivory and other products derived from elephants. However, the international trade in ivory is regulated by Convention on International Trade in Endangered Species (CITES), which recognises that "international co-operation is essential for the protection of certain species of wild fauna and flora against over-exploitation through international trade". Thus, the arguments in favour of ivory trading must refer to conservation objectives, and controversies over the ivory trade have become linked to debates over the management of elephant populations, and ecological assumptions regarding elephant habitat and the resilience or otherwise of savanna ecosystems. In this paper, we examine the ecological aspects of the arguments for a legalised international trade in ivory, and discuss how advances in ecological understanding could influence future discussion of this controversial issue.

Abstract: Abstract The sagebrush-steppe ecosystem covers more than 36 million ha and could play an important role in the global carbon cycle; however, quantitative estimates of CO2 fluxes on these extensive ecosystems are not available. The Bowen ratio/energy balance technique (BREB) was used to continuously monitor CO2 fluxes during the 1996 to 1999 growing seasons at a sagebrush-steppe site near Dubois, Idaho, USA. The daytime and night-time CO2 fluxes were modeled to provide estimates of occasionally missing or aberrant data points so that daily (24-h) integrals across the entire growing season could be quantified. Depending on the particular time of the season, daytime fluxes were best described by a rectangular hyberbolic, nonrectangular hyperbolic, or hysteresis-type functions that included radiation, relative humidity, and soil temperature. Night-time CO2 fluxes exhibited greater variability than daytime fluxes and were not closely correlated with any single meteorological characteristic. Night-time fluxes were predicted using a nonlinear parameter identification technique that estimated values of daytime respiration, which were significantly correlated with night-time fluxes. For the four growing seasons of our study, the integrated seasonal fluxes ranged from 284 to 1,103 g CO2 m-2 with an overall average of 635 g CO2 m-2. Respiratory losses during the non-growing season were estimated to be about 1.5 g CO2 m-2 day-1 or a total of 270 g CO2 m-2. This gives an annual net positive flux (carbon sequestration) estimate of 365 g CO2 m-2 (or 1.0 t C ha-1). These results suggest that the combination of BREB measurements and modeling techniques can be used to provide estimates of CO2 fluxes on important rangeland ecosystems. Das Wüstenbeifu�-Steppenökosystem erstreckt sich über mehr als 36 Millionen Hektar und könnte eine wichtige Rolle im globalen Kohlenstoffkreislauf spielen. Quantitative Schätzungen der CO2-Flüsse dieser ausgedehnten �kosysteme sind jedoch nicht verfügbar. Die "Bowen-Verhältnis"-Energiebilanz-Technik (BREB) wurde benutzt, um die CO2-Flüsse während der Wachstumssaisonen 1996 bis 1999 in einer Wüstenbeifu�-Steppe bei Dubois, Idaho, USA, kontinuierlich zu erfassen. Die Tages- und Nacht-CO2-Flüsse wurden modelliert um Schätzwerte für gelegentlich fehlende oder abweichende Datenpunkte zu bekommen, so dass Tagesintegrale (24h) über die gesamte Wachstumssaison quantifiziert werden konnten. Abhängig vom jeweiligen Zeitpunkt der Saison wurden die Tagesflüsse am Besten durch rechtwinklig hyperbolische, nicht-rechtwinklig hyperbolische oder hystereseähnliche Funktionen beschrieben, die Strahlung, relative Luftfeuchtigkeit und Bodentemperatur enthielten. Die Nacht-CO2-Flüsse zeigten eine grö�ere Variabilität als Tagesflüsse und waren mit keiner einzelnen meteorologischen Kenngrö�e eng korreliert. Die Nachtflüsse wurden vorhergesagt, indem eine nichtlineare Parameter-Identifizierungstechnik verwendet wurde, mit der die Werte der Tagesrespiration geschätzt wurden, die wiederum mit den Nachtflüssen signifikant korreliert waren. Für die vier Wachstumssaisonen unserer Studie bewegten sich die integrierten saisonalen Flüsse zwischen 284 und 1103 g CO2 m-2 mit einem Gesamtmittelwert von 635 g CO2 m-2. Die Respirationsverluste au�erhalb der Wachstumssaison wurden auf ungefähr 1.5 g CO2 m-2 Tag-1 bzw. insgesamt auf 270 g CO2 m-2 geschätzt. Dies ergibt einen geschätzten positiven jährlichen Nettofluss (Kohlenstofffixierung) von 365 g CO2 m-2 (oder 1 t C ha-1). Diese Ergebnisse lassen erkennen, dass eine Kombination von BREB-Messungen und Modellierungstechniken verwendet werden kann, um Schätzungen des CO2-Flusses in wichtigen Weideland-�kosystemen zur Verfügung zu stellen.

Abstract:

Abstract: This paper analyzes the hydrological processes and the impact of soil properties and land use on these processes in tropical headwater catchment in the sub-humid part of Benin (West-Africa), the Aguima catchment. The presented study is integrated in the GLOWA IMPETUS project, which investigates the effects of global change on the water cycle and water availability on a regional scale in Morocco and Benin. The lack of field investigations concerning soil and surface hydrology in the Benin research area necessitates detailed field measurements including measurements of discharge, soil water dynamics, soil physical properties etc. on the local scale in order to understand the dominant runoff generation processes and its influencing factors. This is a pre-requisite to be able to forecast the effects which global change has on hydrological processes and water availability in the region. The paper gives an overview over the hydrologic measuring concept of the IMPETUS-Benin project focusing on measurements concerning the soil saturated conductivity ksat and discharge behaviour of two different sub-catchment of the Aguima catchment. The results of ksat measurements revealed that interflow is the dominant runoff process on the hillslopes of the investigated catchment. Concerning the impact of land use on the hydrological processes infiltration experiments showed that infiltration rates were reduced on cultivated land compared to natural land cover. This results in significant differences in runoff behaviour and runoff ratios while comparing natural and agricultural used catchments.

Abstract: A study on grasshopper assemblage response to seasonal grazing, rotational grazing, continuous resting and continuous grazing was undertaken in the eastern Karoo, South Africa. Rotationally-grazed sites supported the highest number and abundance of grasshopper species while continuously-grazed sites had the lowest. Spring-grazed and winter-grazed sites were the most similar, with continuously-rested sites being the next similar to these. Rotationally-grazed sites showed the least similarity to the other sites. There were clear groupings of sites and grasshopper species, with most species associated with rotationally-grazed sites. Continuously-grazed sites had a different grasshopper assemblage. The assemblages followed definite gradients of measured environmental variables. Rotationally-grazed sites occurred along gradients of increasing bare ground, while continuously-grazed and summer-grazed sites occurred along increasing gradients of shrub cover and soil temperature. Spring-grazed, autumn-grazed, winter-grazed and rotationally-grazed sites were characterized by high vegetation density. Grasshopper dominance differed between sites. Summer-grazed sites had high dominance of Pycnodictya flavipes (40%), winter-grazed sites of Pseudogmothela sp. (32%) The significance of variable grazing management systems for maintaining floral and grasshopper diversity is discussed. Rotational grazing in this arid system is most suited to maintaining plant and insect diversity.

Abstract: Research on the effects of ozone on agricultural crops and agro-ecosystems is needed for the development of regional emission reduction strategies, to underpin practical recommendations aiming to increase the sustainability of agricultural land management in a changing environment, and to secure food supply in regions with rapidly growing populations. Major limitations in current knowledge exist in several areas: (1) Modelling of ozone transfer and specifically stomatal ozone uptake under variable environmental conditions, using robust and well-validated dynamic models that can be linked to large-scale photochemical models lack coverage. (2) Processes involved in the initial reactions of ozone with extracellular and cellular components after entry through the stomata, and identification of key chemical species and their role in detoxification require additional study. (3) Scaling the effects from the level of individual cells to the whole-plant requires, for instance, a better understanding of the effects of ozone on carbon transport within the plant. (4) Implications of long-term ozone effects on community and whole-ecosystem level processes, with an emphasis on crop quality, element cycling and carbon sequestration, and biodiversity of pastures and rangelands require renewed efforts. The UNECE Convention on Long Range Trans-boundary Air Pollution shows, for example, that policy decisions may require the use of integrated assessment models. These models depend on quantitative exposure-response information to link quantitative effects at each level of organization to an effective ozone dose (i.e., the balance between the rate of ozone uptake by the foliage and the rate of ozone detoxification). In order to be effective in a policy, or technological context, results from future research must be funnelled into an appropriate knowledge transfer scheme. This requires data synthesis, up-scaling, and spatial aggregation. At the research level, interactions must be considered between the effects of ozone and factors that are either directly manipulated by man through crop management, or indirectly changed. The latter include elevated atmospheric CO2, particulate matter, other pollutants such as nitrogen oxides, UV-B radiation, climate and associated soil moisture conditions.

Abstract: The effects of burning a native grassland on soil organic matter status was investigated on a long-term (50 years) field experiment where different times and frequencies of burning were compared. Significant decreases in organic C were observed only in the surface 0-2 cm layer and only under annual and biennial winter burning and biennial and triennial autumn burning. Burning in spring did not significantly affect organic C content presumably because substantial amounts of litter decomposed and/or were incorporated into the soil by faunal activity prior to burning. Total N content was decreased substantially to a depth of 6 cm by all burning treatments and as a result, the C:N ratio of soil organic matter was widened. In addition, the amount of potentially mineralizable N, as measured by either aerobic incubation or plant N uptake in a pot experiment, was much reduced. Burning also induced a decrease in light fraction and hot water-extractable C in the 0-2 cm layer but an increase in these parameters, and in microbial biomass C and root density, in the 4-10 cm layer. This was attributed to burning causing a decrease in above-ground litter inputs but increased turnover of root material below the surface. Despite the decrease in organic C and total N content with increasing soil depth, potentially mineralizable N showed the opposite trend. This unexpected finding was confirmed at a nearby site under native grassland and contrasted with decreasing potentially mineralizable N with depth which was measured under a fertilized kikuyu grass dairy pasture. The wide C:N ratio of litter from native grassland, in association with the decreasing size and activity of the microbial biomass with depth results in greater N immobilization (thus less net mineralization) occurring in soil samples taken from close to the soil surface.

Abstract: The development of the main northeast Nigerian river complex, the Komadugu System, is reconstructed, and the possible relation to Holocene environmental changes is investigated. At this stage of research, some field work, concentrating on the lithostratigraphy of the alluvial deposits, has been carried out along the middle and lower courses of the Komadugu Yobe and the Komadugu Gana and is supported by laboratory analyses of sediments and soils. The data obtained so far confirm earlier suggestions that the alluvium can be distinguished into Late Holocene floodplain deposits and a wider, fossilized terrace complex that may reflect a rather palustrine to lacustrine palaeoenvironment possibly related to the Early and Mid-Holocene Lake Megachad.

Abstract: Millions of acres of rangeland in the western United States are now dominated by introduced annual weeds such as cheatgrass (Bromus tectorum L.). The ability to germinate rapidly at low temperatures has been proposed as one of many mechanisms that confer a competitive advantage to this species. Previous studies of this phenomenon, however, have been limited to relatively simple comparisons of total germinability and germination rate under selected constant-temperature treatments. In this study, we germinated seeds of cheatgrass and two native perennial bunchgrass species, bluebunch wheatgrass [Pseudoroegneria spicata (Pursh) Löve] and big squirreltail [Elymus multisetus (J.G. Smith) M.E. Jones], over the temperature range of 0-36 °C and water potential range of 0 to -2.5 MPa. A hydrothermal germination model was constructed to predict germination rate response for the 10, 25 and 50th percentile seed subpopulations. Germination rate estimates were predicted for each species, seedlot and subpopulation for every hour of a 38-year simulation of seedbed temperature and water potential. The seasonal and annual distributions of potential germination rate were integrated to assess relative seedlot response across a wide-range of microclimatic conditions. The integrated response-potential of cheatgrass was consistent with previous studies but the absolute magnitude of enhanced germination rate was relatively small compared to expected differences in seed numbers between cheatgrass and planted species in the field. Historical patterns of seedbed microclimate and predicted germination response may be useful in assessing and optimizing alternative field planting scenarios. Inclusion of weather forecasting and seedbed modeling may provide real-time management options for improving rangeland seeding success.

Abstract: Management of grazing lands has been included in land-based mechanisms for reduction of greenhouse gas emissions. This paper describes a spatial system for scenario analysis of the effect of changes in grazing management on rangeland carbon balances. The system is based on identification of alternative biophysical carbon states and incorporates the effects of management changes and socio-economic and cultural barriers to changes. The management factors include grazing pressure, fire management, control or spread of woody weeds and introduction of browse shrubs. The impact of these factors may be influenced by frequency of good and poor growth years, frequency of droughts and be discounted due to social and economic barriers to adoption. The system appeared to plausibly represent the rangeland responses to management when tested for responses to climate variability and changes in stocking rate, and the impact of prescribed burning in the Tropical Woodlands. Responses are highly sensitive to the knowledge-based estimates of proportion of area in zones for each carbon state and the value of the relative carbon index for each state. A complete and ecologically sound representation of this simple model of carbon state dynamics and climate/vegetation interactions is needed to ensure that scenario analysis is useful and valid for scoping studies.

Abstract: The characteristics of Normalized Difference Vegetation Index (NDVI) time series can be disaggregated into a set of quantitative metrics that may be used to derive information about vegetation phenology and land cover. In this paper, we examine the patterns observed in metrics calculated for a time series of 8 years over the southwest of Western Australia--an important crop and animal production area of Australia. Four analytical approaches were used; calculation of temporal mean and standard deviation layers for selected metrics showing significant spatial variability; classification based on temporal and spatial patterns of key NDVI metrics; metrics were analyzed for eight areas typical of climatic and production systems across the agricultural zone; and relationships between total production and productivity measured by dry sheep equivalents were developed with time integrated NDVI (TINDVI). Two metrics showed clear spatial patterns; the season duration based on the smooth curve produced seven zones based on increasing length of growing season; and TINDVI provided a set of classes characterized by differences in overall magnitude of response, and differences in response in particular years. Frequency histograms of TINDVI could be grouped on the basis of a simple shape classification: tall and narrow with high, medium or low mean indicating most land is responsive agricultural cover with uniform seasonal conditions; broad and short indicating that land is of mixed cover type or seasonal conditions are not spatially uniform. TINDVI showed a relationship to agricultural productivity that is dependent on the extent to which crop or total agricultural production was directly reduced by rainfall deficiency. TINDVI proved most sensitive to crop productivity for Statistical Local Areas (SLAs) having rainfall less than 600 mm, and in years when rainfall and crop production were highly correlated. It is concluded that metrics from standardized NDVI time series could be routinely and transparently used for retrospective assessment of seasonal conditions and changes in vegetation responses and cover.

Abstract: Fire was arguably the most important forest and rangeland disturbance process in the Inland Northwest United States for millennia. Prior to the Lewis and Clark expedition, fire regimes ranged from high severity with return intervals of one to five centuries, to low severity with fire-free periods lasting three decades or less. Indoamerican burning contributed to the fire ecology of grasslands and lower and mid-montane dry forests, especially where ponderosa pine was the dominant overstory species, but the extent of this contribution is difficult to quantify. Two centuries of settlement, exploitation, management, and climate variation have transformed the fire regimes, vegetation and fuel patterns, and overall functionality of these forests. We present a narrative that portrays conditions beginning at the first contact of Euro-American settlers with Indoamericans of the region and extending to the present. Due in part to its geographic isolation, the Inland Northwest was among the last regions to be discovered by Euro-Americans. In 200 years the region has undergone fur trapping and trading, sheep, cattle, and horse grazing, timber harvesting, mining, road construction, native grassland conversion to agricultural production, urban and rural area development, fire prevention, and fire suppression. We highlight key changes to forest landscape patterns and processes that occurred under these combined influences, discuss implications of the changes, and progress towards restoring sustainability. An adaptive ecosystem management model has been adopted by public land management agencies to remedy current conditions. Ecosystem management is a relatively new concept that emphasizes the integrity and sustainability of land systems rather than outputs from the land. Adaptive management emphasizes the twin notions that incomplete knowledge and high degrees of risk and uncertainty about earth and climate systems will always limit land and resource planning and management decisions, and that management is chiefly a learning and adapting process. We discuss current issues and future options associated with ecosystem management, including the low likelihood of social consensus concerning desired outcomes, the lack of integrated planning, analysis, and decision support tools, and mismatches between existing land management planning processes, Congressional appropriations, and complex management and restoration problems.

Abstract: Fires in African savannas produce emissions contributing to changes in global biogeochemical processes. In the Southern African Regional Science Initiative (SAFARI-2000), fuels characteristics were measured before and after experimental burns in two different western Zambian grassland types (dambo and flood plain) situated on Kalahari Sands. The two land use types did not differ in terms of fuel characteristics, fire behavior or combustion completeness. As a consequence of a significantly wet year, fuel loads and moisture content were higher than those found during SAFARI-92. Use of moisture content and fire behavior component could increase the emission estimation through the fuel consumption calculation. Ranges of estimated emissions for CH4 and NMHC were lower than previously stated.

Abstract: A grazing gradient in Grand Staircase-Escalante National Monument, UT was identified with field measurements and spectral mixture analysis (SMA) of remotely sensed hyperspectral imagery. Grazing gradient persistence during a period of above-average rainfall was confirmed with multi-temporal Landsat imagery. SMA yielded accurate sub-pixel fractional cover measurements of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV) and bare soil, and revealed a clear trend of increasing PV and NPV and decreasing bare soil with distance from water. The effect of topographic slope on cover fractions with distance from water was investigated and indicated that cover fraction values are tightly coupled to slope and distance from water. Results showed that on steeper slopes, fractional cover of PV and bare soil increased while NPV decreased. The fundamental relationship of changing cover fractions with distance from water was preserved within all slope classes. This work shows how imaging spectroscopy can be used to assess rangeland condition by demonstrating its ability to detect fine scale variations in cover fractions known to be sensitive to grazing. The study indicates the potential for routine assessment of rangeland resources with current and future spaceborne hyperspectral imaging systems.

Abstract: Little is known regarding the effects of land use on soil organic matter status and earthworm communities in South African soils. For that reason the effects of the main agricultural land uses in the midlands region of KwaZulu-Natal (maize (Zea mays), sugarcane (Saccharum spp.), annual ryegrass (Lolium multiflorum), permanent kikuyu pasture (Pennisetum clandestinum), gum (Eucalyptus grandis) and pine forest (Pinus patula)) on soil organic matter content, microbial biomass C and the size and composition of the earthworm community was investigated on two sites where the long-term history of land management was known. In comparison with, undisturbed, native grassland, permanent kikuyu pasture resulted in an increase in organic C, K2SO4-extractable C, microbial biomass C and the microbial quotient. Maize and sugar production under conventional tillage (CT) resulted in a decrease in organic matter and microbial biomass. Under gum and pine forests the organic C content was similar to that of under native grassland but the microbial biomass and microbial quotient tended to be higher. Exotic earthworms dominated under agricultural management making up to 98 and 100% of the communities at sites 1 and 2, respectively. They belonged to the families Lumbricidae, Acanthrodilidae and Megascolicidae. They were accidentally introduced from Europe, India and West Africa, respectively, and now coexist in the sub-humid warm climate of the region. Earthworm numbers (230-310 m-2) and biomass, the number of species present, and the number present as adults were all greatest under kikuyu pastures and numbers were low (<60 m-2) under maize (CT) and sugarcane. Numbers were 3.5-fold higher for maize under zero than CT. In relation to the comparatively large organic C and microbial biomass C values under exotic forests, earthworm numbers were notably low (25-60 m-2). This was attributed to the low palatability of pine and gum litter. It was concluded that land use has substantial effects on soil organic matter content and on the size, composition and diversity of earthworm communities in South African soils.

Abstract: Bitterweed is one of the most detrimental poisonous plants to sheep production in west central Texas. Sheep typically avoid the plant unless alternative forage is limited. When consumption does occur, some flocks and individuals are able to consume bitterweed and avoid toxicosis. Our objective was to determine the importance of site of origination (long-term exposure), experiences early in life (short-term exposure), and sire selection on the ability to avoid bitterweed toxicity. In Trial 1, we compared bitterweed intake of 15 ewes originating from bitterweed-infested and 15 ewes from bitterweed-free rangelands. Bitterweed intake of their half-sib offspring was compared in the subsequent year. Ewes from bitterweed-infested rangelands ate more (P<0.05) bitterweed, but lambs born to ewes from bitterweed-free rangelands consumed more (P<0.05) bitterweed. In Trial 2, we compared intake of 40 lambs from two separate ewe flocks (20 from each flock). One flock of ewes originated from bitterweed-infested rangelands, the other from bitterweed-free rangelands. Each flock was divided in half so that irrespective of origin of the ewes, lambs from both flocks would be born and reared (birth to weaning) in each habitat. Lambs from flocks originating from bitterweed-free rangelands consumed more bitterweed than lambs from bitterweed-infested rangelands, regardless of site of rearing. During Trials 2 and 3, we also assessed the influence of sire on bitterweed intake. Offspring from three sires in Trial 2 consumed different (P<0.05) amounts of bitterweed, but sires were confounded with origin. In Trial 3, offspring from five unrelated sires consumed similar amounts of bitterweed. Thus, the ability to consume bitterweed does not appear to be strongly influenced by the sire's genetic characteristics. Likewise, experience with bitterweed early in life does not appear to lead to greater consumption later in life. Thus, manipulating feeding behavior does not appear to be a viable management option at this time for reducing the likelihood of bitterweed toxicosis.

Abstract: In a naturally heterogeneous landscape in arid central Australia, a previous study found that grazing changed the distribution of water and nutrients amongst different geomorphic strata of the landscape. In this concurrent study, we show that herbage biomass, cover and composition responded primarily to these geomorphic strata and not to grazing. The cover of palatable species as a group proved the exception, and decreased with increasing grazing. The quantity of shrubs responded to both strata and grazing, and was greatest under least grazing. We suggest several potential reasons for the failure of damaged sites and strata to recover.

Abstract: Sustaining the productive capacity of the land resource under the existing land-use system and increasing population pressure requires the use of appropriate technologies that will enhance farm productivity and income levels. This paper examines the effect on farm profitability of smallholder maize farmers' use of intensification technologies in tropical agriculture. The survey was conducted in southwest Nigeria. A multi-stage sampling technique was used to select 300 respondents from two major agroclimatic zones in Osun State. Primary data were collected using a structured questionnaire and complemented with focus group discussions (FGDs), while the State's Ministry of Agriculture provided secondary data. Pressure on land was found high because farmland was continuously cropped for an average of 10 years with a mean fallow period of 2 years only. Technologies used to intensify agriculture included inorganic fertilizer, organic manure, alley cropping, and tree planting. Results from costs and returns analysis showed that average net returns to inorganic fertilizer use ranked highest in the two zones, while tree planting ranked lowest. There was a significant ecoregional difference on the average net returns/year earned by users of mineral fertilizer. While organic manure use earned higher net returns than alley cropping practice in the rain forest, the reverse was the case for the derived savanna. FGDs revealed that respondents' preferred to use inorganic fertilizer despite its inadequate supply because, apart from enhancing higher returns and net gains, it also improved output level and provided an opportunity for the continuous use of the scarce land. These results imply that economic returns play a critical role in farmers' use of intensification technologies and consequently affect their resource management decisions. Policy measures aimed at promoting research on appropriate technologies that are profitable on farmers' fields will be more effective in enhancing farmers' use of intensification technologies.

Abstract: This paper contributes to the debate over land tenure in rural China by extending its spatial coverage to the country's extensive rangeland regions. Key characteristics of pastoral tenure, identified from field appraisals in western China, include group tenure and fuzzy boundaries. Although these characteristics give rise to efficiency concerns, from a new institutional economics perspective they also facilitate the realization of certain benefits, benefits that could represent opportunity costs of further exclusiveness. The strengthening of rangeland co-management may constitute a more appropriate path to institutional improvement than the establishment of the household ranch, the current goal of national rangeland policy.

Abstract: The ornamental hybrid shrub, Lantana camara L. (lantana), is a serious environmental weed and has been targeted for biological control in South Africa since 1961. The established biocontrol agents cause insufficient levels of damage and additional natural enemies are required to reduce the invasiveness of this weed. The lantana mirid, Falconia intermedia (Distant), is a promising new agent that was imported from the Caribbean for life history and host-range studies. The nymphs and adults are leaf-suckers that cause chlorotic speckling, which reduces the photosynthetic capacity of the plant. Biological studies indicate that F. intermedia has considerable biocontrol potential, in that it has a high intrinsic rate of increase, the potential for multiple generations a year, highly mobile adults, and a high level of damage per individual. Host-specificity trials indicated that the lantana mirid has a narrow host range, with L. camara being the most suitable host, but several indigenous African species in the closely related genus Lippia are suitable alternative host plants. Under multiple-choice conditions, adults showed a significant and strong oviposition preference for L. camara over the Lippia species. A risk assessment of potential nontarget effects indicated that three Lippia species could sustain damage levels in the field. The relatively low probability of damage to indigenous species was considered a justified trade-off for the potentially marked impact on L. camara. The regulatory authorities accepted the results of this study and F. intermedia was released against L. camara in South Africa in April 1999.

Abstract: 1. Rangeland ecologists have been debating the validity of two current paradigms for the evaluation of vegetation dynamics on rangelands. This debate frequently contrasts the conventional model of continuous and reversible vegetation dynamics (range model) with a more contemporary model that can accommodate discontinuous and non-reversible vegetation change (state-and-transition model). 2. The range and the state-and-transition models are conceptually related to the equilibrium and non-equilibrium paradigms within ecology, respectively. The methodological dichotomy that has developed between the range and the state-and-transition models has fostered the perception that these two ecological paradigms are mutually exclusive. We challenge this perception and contend that both methodologies and their corresponding paradigms are non-exclusive. 3. Equilibrium and non-equilibrium ecosystems are not distinguished on the basis of unique processes or functions, but rather by the evaluation of system dynamics at various temporal and spatial scales. Consequently, ecosystems may express both equilibrium and non-equilibrium dynamics. This confirms early interpretations that ecosystems are distributed along a continuum from equilibrium to non-equilibrium states. 4. Although both equilibrium and non-equilibrium dynamics occur in numerous ecosystems, the empirical evidence is frequently confounded by (i) uncertainty regarding the appropriate evidence necessary to distinguish between paradigms; (ii) disproportionate responses among vegetation attributes to climate and grazing; (iii) comparisons among systems with varying degrees of managerial involvement; and (iv) the evaluation of vegetation dynamics at various spatial and temporal scales. 5. Synthesis and applications . This critique supports the conclusion that a paradigm shift has not taken place in rangeland ecology, but rather, the debate has forced a more comprehensive interpretation of vegetation dynamics along the entirety of the equilibrium-non-equilibrium continuum. Therefore, the rangeland debate should be redirected from the dichotomy between paradigms to one of paradigm integration.

Abstract: Abstract The distribution and abundance of trees can be strongly affected by disturbance such as fire. In mixed tree/grass ecosystems, recurrent grass-fuelled fires can strongly suppress tree saplings and therefore control tree dominance. We propose that changes in atmospheric [CO2] could influence tree cover in such metastable ecosystems by altering their postburn recovery rates relative to flammable herbaceous growth forms such as grasses. Slow sapling recovery rates at low [CO2] would favour the spread of grasses and a reduction of tree cover. To test the possible importance of [CO2]/fire interactions, we first used a Dynamic Global Vegetation Model (DGVM) to simulate biomass in grassy ecosystems in South Africa with and without fire. The results indicate that fire has a major effect under higher rainfall conditions suggesting an important role for fire/[CO2] interactions. We then used a demographic model of the effects of fire on mesic savanna trees to test the importance of grass/tree differences in postburn recovery rates. We adjusted grass and tree growth in the model according to the DGVM output of net primary production at different [CO2] relative to current conditions. The simulations predicted elimination of trees at [CO2] typical of the last glacial period (180 ppm) because tree growth rate is too slow (15 years) to grow to a fire-proof size of ca. 3 m. Simulated grass growth would produce an adequate fuel load for a burn in only 2 years. Simulations of preindustrial [CO2] (270 ppm) predict occurrence of trees but at low densities. The greatest increase in trees occurs from preindustrial to current [CO2] (360 ppm). The simulations are consistent with palaeo-records which indicate that trees disappeared from sites that are currently savannas in South Africa in the last glacial. Savanna trees reappeared in the Holocene. There has also been a large increase in trees over the last 50�100 years. We suggest that slow tree recovery after fire, rather than differential photosynthetic efficiencies in C3 and C4 plants, might have been the significant factor in the Late Tertiary spread of flammable grasslands under low [CO2] because open, high light environments would have been a prerequisite for the spread of C4 grasses. Our simulations suggest further that low [CO2] could have been a significant factor in the reduction of trees during glacial times, because of their slower regrowth after disturbance, with fire favouring the spread of grasses.

Abstract: This paper describes a methodology of using data acquired by the European Meteosat and the Japanese Geostationary Meteorological Satellite (GMS) geostationary satellites to detect burned areas in different tropical environments. The methodology is based on a multiple threshold approach applied to the thermal radiance and to a spectral index specific for burned surfaces. The Simple Index for Burned Areas (SIBA), also developed in this study, makes use of the information contained in the visible and thermal InfraRed (IR) band available on the geostationary satellites, whose main advantages are the high temporal resolution and the minimal level of pre-processing required. The results obtained with Meteosat data have been evaluated comparing them with NOAA-Advanced Very High Resolution Radiometer (AVHRR) data acquired over the Central Africa forest-savannah areas. For GMS imagery, AVHRR data acquired over the woodland-savannah areas of Northern Territory in Australia have been used. Despite the very low spatial and spectral resolution of the data, accuracy assessment showed at a regional and continental scale the resulting burned area maps could be a valuable source of information for the monitoring of the fire activity and for the assessment of fire impact on tropospheric chemistry.

Abstract: This paper describes a new procedure for hydrological data collection and assessment of agricultural and environmental water use using public domain satellite data. The variability of the annual water balance for Sri Lanka is estimated using observed rainfall and remotely sensed actual evaporation rates at a 1 km grid resolution. The Surface Energy Balance Algorithm for Land (SEBAL) has been used to assess the actual evaporation and storage changes in the root zone on a 10-day basis. The water balance was closed with a runoff component and a remainder term. Evaporation and runoff estimates were verified against ground measurements using scintillometry and gauge readings respectively. The annual water balance for each of the 103 river basins of Sri Lanka is presented. The remainder term appeared to be less than 10% of the rainfall, which implies that the water balance is sufficiently understood for policy and decision making. Access to water balance data is necessary as input into water accounting procedures, which simply describe the water status in hydrological systems (e.g. nation wide, river basin, irrigation scheme). The results show that the irrigation sector uses not more than 7% of the net water inflow. The total agricultural water use and the environmental systems usage is 15 and 51%, respectively of the net water inflow. The consumptive use of rain-fed and irrigated agriculture are approximately equal. The evaporation rates in agriculture and mixed vegetation are similar, so that low productivity rangelands can be transformed into rain-fed agriculture without detrimental effects on water availability to downstream users. The unused water flow to the Indian Ocean is 34% of the net inflow, hence there is scope for further water developments in Sri Lanka.

Abstract: The new species Streptocarpus lilliputana (Gesneriaceae), collected on the Pondoland coast, South Africa, is described. Although its alliances are not obvious in terms of corolla morphology and rosulate habit, it approaches S. gardenii and its allies. The pollen and stigma of S. lilliputana differ markedly from the stenopalynous grains and bilobed stigmas of the other South African rosulate species. Streptocarpus lilliputana is exceedingly rare and is a further endemic from the Pondoland centre.

Abstract: We examined relationships between vegetation and soil nutrients along rainfall and land use gradients in the Kalahari. Soil organic carbon (SOC) was significantly lower where reduced rainfall and grazing lowered litter inputs to the soil. Soil organic nitrogen (SON) was significantly lower at the driest site and was higher than expected at two grazed sites. Ammonium levels at Mongu (wettest) were significantly higher, while nitrate was lower than expected everywhere. Site-averaged concentrations showed no significant differences in SOC and SON beneath plant canopies, but woody plant canopies alone showed elevated SOC at three sites and SON at one site.

Abstract: Sr and Ba levels of two proximal aragonite speleothems from Cold Air Cave, South Africa, are examined at [mu]m resolution. A compositional map derived from parallel secondary ion mass spectrometry linescans indicates heterogeneity perpendicular to the stalagmite growth axis, precluding the use of single linescans as a climatic proxy technique. A ~40-yr averaged trace element record for the cave produced from multiple parallel linescans on both stalagmites is compared with regional and local climatic (rainfall, temperature) data for 1955-1996. This period includes two extensive drought episodes. There is poor correlation between trace elements and annual mean temperature. Droughts correspond to minima in trace element ratios and peaks correspond to annual maxima in rainfall. The onset and termination of droughts are notable inflexions. However, in detail annual rainfall magnitude does not correlate directly with trace element ratios, indicating that kinetic factors, notably variations in speleothem growth rate, play a key role in trace element uptake by aragonite. Averaged long data sets constrained by chronological control have potential in the study of sub-decadal precipitation patterns.

Abstract: This paper examines the shareholder wealth effects associated with global equity offerings made by foreign firms after their initial cross-listing in the United States. We document that the market reaction to seasoned global equity offerings is economically and statistically insignificant. However, it is 1.5% larger than the market reaction to offerings made on local exchanges only. In addition, we find that the adverse market reaction to local equity offerings is mitigated as more capital is raised globally. Our findings support the hypothesis that global capital raising is associated with significant benefits.

Abstract: This study aimed at identifying plant species with potential for rangeland conservation and to provide livestock feed in Oman. A survey was carried out in Al-Khod region near Muscat (Oman) to identify potential grass species. Samples were collected from various sites during the rainy season (November-April) to study the morphology and chemical composition of selected grasses. Cenchrus and Pennisetum species were the most promising grasses in terms of livestock feeding. The yield of pasture dominated by Cenchrus was higher than that reported for the species in other countries with a similar arid environment and comparable to grasses grown in Oman under irrigation. Relevant meteorological records indicated that the grasses had good potential to withstand shortage of water. The germination test on burs and seeds showed high dormancy reflecting ability to survive under uncertain rainfall and potential for survival under rangeland conditions. Storage of seeds for a period of 1 year improved their germination up to 66%. Variation in morphological traits indicated the suitability of grasses to develop varieties for commercial use under farm or rangeland conditions.

Abstract: Soils are a major location of carbon (C) storage in most terrestrial ecosystems and changes in soil C pools therefore play an important role in the C cycle. Human conversion of native ecosystems to agro-ecosystems, overgrazing and lack of agricultural management influence the amount, quality and turnover of soil organic carbon (SOC). This paper focuses on changes in reactivity, distribution and total stocks of SOC in the upper 1 m of soils representing savanna as well as groundnut (Arachis hypogaea L.) and millet (Pennisetum glaucum L.) fields cultivated for up to 40 years within the semi-arid part of Senegal. The soil C stock varied from 4.4 kg C m-2 in open woodland savanna to 2.7 kg C m-2 in grass savanna. Clearing and cultivation of savanna land has resulted in a loss of SOC up to 24% in the upper 1 m equal to 1.1 kg C m-2 over 40 years, or more than six times the short-term C loss associated with clearing of above-ground biomass in nowadays semi-arid savanna in Senegal. Observed SOC losses the first 4-8 years following cultivation were consistent for all sites, whereas observed long-term losses suggest important variations related to a north-south (N-S) climatic gradient across the region. Laboratory respiration measurements reveal similarity with respect to SOC reactivity, which is consistent with the observations of significant higher soil CO2 effluxes from savanna soils than cultivated soils. The results call for further attention on region-specific changes in SOC stocks (time scales) due to cultivation and improved understanding of the long-term controls of SOC cycling after clearing of tropical savanna.

Abstract: We examined changes in rangeland health in the semi-arid woodlands of eastern Australia at fixed sites between 1989 and 1999. Over the 11-year period there were significant declines in the quality of the vegetation, and changes in plant species were driven largely by seasonality, and to a lesser extent, amount of rainfall. Three indices of rangelands health (composition, function and stability) developed using site-based vegetation and landscape data, indicated that the majority of sites had intermediate values of the three indices, and few sites had either very low or very high values. The indices of composition and function were strongly correlated with the subjective ratings applied to each site at each measurement period. The results of this study highlight the difficulty of detecting change over extensive areas of rangeland, and of separating management-induced effects from climatic effects in an environment which experiences wide spatial and temporal variation in rainfall.

Abstract: A distinguishing, co-dominance feature of trees and grasses in Savannas was prominently explained by Walter. He hypothesized that water is the limiting factor and grasses are superior competitors for water in the upper soil, while trees have exclusive access at deeper layers. However, a new field evidence from the Kalahari, where the water table is too low for the tree roots' tapping, revealed that both plant types invest the bulk of their roots in the surface horizons. Further investigation should consider focusing on determining the co-dominance mechanism of both plant types without the displacement of the less-efficient species.

Abstract: Abstract 10.1002/hyp.1170.abs As stated by many authors in the recent past, soil erosion is one of the major environmental problems in southern Africa and it will become even more severe in the future due to population growth and potential climatic changes. This study concerns the detection of different land degradation stages in semi-arid grassland areas in the upper Mbuluzi-river catchment (Kingdom of Swaziland). It has been carried out within the framework of an interdisciplinary EU-funded project aimed at developing an integrated water resources management system (IWRMS) for water resources analyses and prognostic scenario planning in semi-arid catchments of Southern Africa (Flügel et al., 2001 URL: http://www.iwrms.uni-jena.de/download/Eu-reports/report_final.pdf). Within this more general framework, particular attention was focused on the determination of high-resolution morphometric parameters for detailed erosion process studies, as well as on the derivation of relationships between vegetation cover and bare soil. The latter has subsequently been used to delineate the vegetation cover density and C-factor values for erosion models such as the revised universal soil loss equation. The examples from Southern Africa show that the methods applied are able to identify areas affected by different types of erosion. Furthermore, it is possible to estimate the parameters for a subsequent erosion modelling. Copyright © 2003 John Wiley & Sons, Ltd.

Abstract: Soil organic C (SOC) concentrations in topsoil samples taken at 678 sites in the grassland of Ireland were investigated using statistics and geostatistics. SOC concentrations (Walkley-Black method) follow a lognormal distribution, with a median and geometric mean of 5.0%, and an arithmetic mean of 5.3%. Statistically significant (P<0.01) positive correlation between SOC and silt-plus-clay, and negative correlation between SOC and sand were observed, with lower correlation (P=0.17) between SOC and pH. Lower SOC concentrations were associated with higher percentages of land in tillage. In order to obtain a robust measurement of spatial structure, spatial outliers were detected, and subsequently eliminated, using the local Moran's I index. The spatial distribution of SOC concentrations based on kriging interpolation showed coherent spatial patterns, with the highest values in the western coastal area, and relatively low values in the inland and southeastern coastal areas; soils at higher elevation were also found to contain higher SOC concentrations. These patterns are consistent with the distribution of rainfall within the country.

Abstract: John Acocks' ideas on the recent and future changes of vegetation in South Africa occupy an important conceptual position in the first and subsequent editions of Veld Types of South Africa. Arguably the most prominent idea embodied in his discussion of vegetation changes is the hypothesis that various Karoo veld types were expanding eastwards and northwards into areas that would otherwise be occupied by grassland, and that this process was a direct result of mismanagement of the semi-arid rangelands. The invasion of Karoo vegetation amounts to a systematic consideration in South Africa of what would ultimately become known as desertification. This paper examines Acocks' interpretation of the vegetation changes associated with expanding Karoo and desert veld types and his evidence that this was indeed occurring. It places the apparent degradation into an appropriate historical context in relation to the evolving views of other South African and international scientists. The paper shows how Acocks' understanding of vegetation dynamics influenced agricultural policy, both immediately following publication of Veld Types and subsequently. Finally, a critique of the spreading Karoo hypothesis is developed in relation to current theory on desertification and its implications for management of the semi-arid rangelands of South Africa today.

Abstract: The Western Cape Province of South Africa has a long history of human occupation and utilisation; the impact of colonial settlement (late 17th century onwards) on agriculture has been especially prominent. The Mediterranean-type climate of the Western Cape results in landscapes which are potentially susceptible to land degradation, perhaps even desertification. The Swartland is a gently undulating inland plateau underlain largely by fine-grained and nutrient-rich shales of the pre-Cambrian Malmesbury group. Agriculture is the dominant land use to the extent of wholesale landscape transformation. The area has been subject to significant levels of land degradation in the past, manifesting itself as widespread gully erosion. During the 1940s, the region was described as on the verge of economic collapse due to the severity of soil erosion, but concerted soil conservation and education efforts under the political dispensation of the time appear to have averted that scenario. The region now faces the combined challenges of potentially rapid climate change under a considerably altered socio-economic and political order. Downscaled climate change scenarios facilitate a regional assessment of changes in the parameters affecting soil erosion susceptibility in the Swartland and leads to a consideration of the implications of such scenarios for the continuation of contemporary land use practices.

Abstract: We review various recent approaches to making digital soil maps based on geographic information systems (GIS) data layers, note some commonalities and propose a generic framework for the future. We discuss the various methods that have been, or could be, used for fitting quantitative relationships between soil properties or classes and their [`]environment'. These include generalised linear models, classification and regression trees, neural networks, fuzzy systems and geostatistics. We also review the data layers that have been, or could be, used to describe the [`]environment'. Terrain attributes derived from digital elevation models, and spectral reflectance bands from satellite imagery, have been the most commonly used, but there is a large potential for new data layers. The generic framework, which we call the scorpan-SSPFe (soil spatial prediction function with spatially autocorrelated errors) method, is particularly relevant for those places where soil resource information is limited. It is based on the seven predictive scorpan factors, a generalisation of Jenny's five factors, namely: (1) s: soil, other or previously measured attributes of the soil at a point; (2) c: climate, climatic properties of the environment at a point; (3) o: organisms, including land cover and natural vegetation; (4) r: topography, including terrain attributes and classes; (5) p: parent material, including lithology; (6) a: age, the time factor; (7) n: space, spatial or geographic position. Interactions (*) between these factors are also considered. The scorpan-SSPFe method essentially involves the following steps: (i) Define soil attribute(s) of interest and decide resolution [rho] and block size [beta].(ii) Assemble data layers to represent Q.(iii) Spatial decomposition or lagging of data layers.(iv) Sampling of assembled data (Q) to obtain sampling sites.(v) GPS field sampling and laboratory analysis to obtain soil class or property data.(vi) Fit quantitative relationships (observing Ockham's razor) with autocorrelated errors.(vii) Predict digital map.(viii) Field sampling and laboratory analysis for corroboration and quality testing.(ix) If necessary, simplify legend or decrease resolution by returning to (i) or improve map by returning to (v). Finally, possible applications, problems and improvements are discussed.

Abstract: The effect of intensive grazing and browsing of domestic stock and wildlife on the number of species and abundance of vegetation was investigated in the Hoanib River catchment, north-western Namibia. The seasonal abundance of ground cover, bare earth, canopy cover, annual grass, perennial grass and annual forbs were measured in each of the focus-study areas. In three of the focus areas where the ranges of both domestic stock and wildlife were restricted either by fencing or water availability, impact on the vegetation was greatest. The final focus area was a more [`]open range' system that allowed for the free movement of wildlife. Under these conditions the species abundance and availability of browsing and grazing was greater than the other focus areas during both the wet and dry seasons. However, very little difference in abundance and availability of vegetation was observed between focus areas in both seasons regardless of landuse. There is generally a low abundance of perennial grasses and browse species affording the ecosystem little resistance and resilience to disturbance caused by grazing and drought.

Abstract: A hydrological modelling at a catchment scale has been used to investigate the impact of climatic and land use change on water resources in data scarce Tropical Africa using a distributed precipitation-runoff modelling system. The model divides a catchment into homogeneous hydrological response units, providing the ability to impose changes in climate or land use spatially. Model parameters were either estimated from different existing data or by calibration against measured discharge data available over 11 years (1985-1995). The model simulation-period was divided into calibration (1986-1990) and validation (1991-1995) periods. The model provided relatively good fits between measured and simulated discharge both at a daily and monthly scales. Based on sensitivity analyses, a 10% decrease in rainfall produced a 30% reduction on the simulated hydrologic response of the catchment, while a 1.5 °C increase in air temperature would result in a decrease in the simulated discharge of about 15%. Converting the present day dominantly cultivated/grazing land in the studied river basin by woodland would decrease the discharge at the outlet by about 8%. In order to use the results of this kind of model for decision making and water resources management, the model should be tested under different environment and different scenario conditions. Rainfall measurement and stage-discharge rating curves should be given priority to improve model performance.

Abstract: The numbers of livestock and wildlife that can be supported in an arid environment such as the Hoanib River catchment, north-western Namibia, are determined by annual and seasonal availability of grazing and browsing. The availability and abundance of vegetation was investigated in eight focus-study areas across the catchment. The vegetation of the focus area was observed to behave in a non-equilibrial manner in that it was dependent on annual rainfall rather than intensity of landuse. The Zurich-Montpellier method of vegetation assessment was used for the evaluation of vegetation plots. The amount of dry season grazing was also dependent on the previous season's rainfall, with [`]dead grass' and perennial grass only available after an [`]above average' rainfall season. Vegetation communities were dominated by mixedColosphosermum mopane woodlands in the 100-350 mm rainfall zone, while perennial grasses dominated the 50-100 mm rainfall zone. While the bulk rangeland appeared not to be disturbed by landuse, a 2 km [`]sacrifice zone' around water sources was found to have changes in vegetation species and abundance. During below-average rainfall seasons and drought, when there is limited or no grazing, browse becomes the most important source of nutrition for domestic stock and wildlife.

Abstract: Criteria and indicators (C&I) have become primary tools in implementing the principle of sustainable resource management. To carry out this principle, it is necessary to develop methodologies that can holistically and systematically generate relevant indicators for a particular forest or resource management unit. This paper describes some methodologies that can be used as tools to carry out structured analysis of C&I. Multi-criteria analysis (MCA) is used as a decision-making tool to analyze and evaluate multiple C&I under a participatory group decision-making environment. Use of the method enables the generation of C&I, estimation of their relative importance, estimation of the performance of each indicator relative to its desired condition, and assessment of the indicators' combined effect or impact. In addition to generating C&I and estimating their relative importance and performance, the paper also presents a soft methodology, called cognitive mapping, which can be used to assess the cross-indicator interaction, linkages, and connectivities of the indicators. The method attempts to evaluate the overall cumulative impacts of all indicators, individually and collectively, as they impact sustainability directly and indirectly through their interactions with other indicators.

Abstract: The authors propose an original modelling methodology to investigate grazing systems, which confronts and combines two conceptually and methodologically different approaches that link two contrasting points of view on the grazing system: a farmer's organisation of grazing and changes in plant cover states on the farm territory. The methodology consists of a multivariate analysis enabling the modelling of changes in the plant cover to be interpreted in the light of the farmer's grazing practices by applying a model of farmer behaviour for action. One objective was to determine the relative role of vegetation in the farmer's decisions on the grazing management, in particular by highlighting the farmer's strategic organisation rules and adaptation to change. The research is based on a 2-year case study of a sheep farm using chiefly native vegetation and some improved grass in the calcareous hills of inland Provence in southeastern France. The farm is representative of one of the meat sheep farming types of southeastern France producing mainly housed lambs raised exclusively on suckling and concentrate and sold at 100-120 days at a carcass weight of 15-18 kg. The two successive study years were selected for their greatly contrasting weather conditions. In this situation, adjustments made by the farmer were shown to be peripheral and consisted of either combining the use of certain fields, or securing the use of complementary fields from neighbours. Thus this paper aims to enable both scientists and agricultural advisers to better understand different aspects of the ways the system operates and the factors influencing its management.

Abstract: The KwaZulu-Natal region of South Africa hosts a large diversity of asclepiads (Apocynaceae: Asclepiadoideae), many of which are endemic to the area. The asclepiads are of particular interest because of their characteristically highly evolved floral morphology. During 3 months of fieldwork (November 2000 to January 2001) the flower visitors and pollinators to an assemblage of nine asclepiads at an upland grassland site were studied. These observations were augmented by laboratory studies of flower morphology (including scanning electron microscopy) and flower colour (using a spectrometer). Two of the specialized pollination systems that were documented are new to the asclepiads: fruit chafer pollination and pompilid wasp pollination. The latter is almost unique in the angiosperms. Taxa possessing these specific pollination systems cluster together in multidimensional phenotype space, suggesting that there has been convergent evolution in response to similar selection to attract identical pollinators. Pollination niche breadth varied from the very specialized species, with only one pollinator, to the more generalized, with up to ten pollinators. Pollinator sharing by the specialized taxa does not appear to have resulted in niche differentiation in terms of the temporal or spatial dimensions, or with regards to placement of pollinaria. Nestedness analysis of the data set showed that there was predictability and structure to the pattern of plant-pollinator interactions, with generalist insects visiting specialized plants and vice versa. The research has shown that there is still much to be learned about plant-pollinator interactions in areas of high plant diversity such as South Africa.

Abstract: Livestock may impact habitat quality for grasshoppers by reducing food availability and by altering microclimate and potential oviposition sites. A 5-year study was conducted to create consistent grazing impacts on replicated plots and measure their effects on plant cover, microclimate, and grasshopper abundance. Cattle were used to produce two levels of grazing intensity that were compared to ungrazed controls. Differences in plant cover were greatest immediately after grazing each summer, grasshopper microhabitats tending to be shadier, cooler, less windy, and more humid in the ungrazed plots. The grasshopper assemblage included five of the worst pest grasshopper species in North America: Ageneotettix deorum, Aulocara elliotti, Melanoplus sanguinipes, M. packardii, and Camnula pellucida. Most species had greater abundance on ungrazed pastures, particularly during the 4-6 weeks after grazing each year. However, A. elliotti was often more abundant in heavily grazed areas early in the year when early instars were present and in late summer when adults were predominant. There was no strong evidence that the effect of grazing on grasshopper abundance increased over the 5-year study. At this time, all changes in grasshopper numbers cannot be directly attributed to particular habitat characteristics that changed after grazing, but the results suggest that grazing management could be used to reduce pest grasshopper densities.

Abstract: Acocks measured representative sites of good condition grassland in the 1940's that were re-sampled approximately 50 years later in order to compare the effect of commercial versus communal grazing on compositional change. Most of the Mistbelt 'nGongoni Veld had been afforested, a third of Highland Sourveld or Northern Tall Grassveld had been transformed by cultivation or afforestation, while most of Southern Tall Grassveld had remained as grassland. For untransformed sites sampled in 1996, the composition of communally and commercially grazed land differed distinctly, although differences depended on an altitudinal gradient reflecting water availability. Sites under communal grazing supported a higher proportion of short-lived, perennial grass species, often of poor grazing value. From measurement of the extent of compositional change of each site, commercially grazed sites showed no consistent pattern of change, and the average extent of change was small. By contrast, communally grazed sites had on average changed considerably, although the direction of change had depended on the physical environment. Basal cover increased with altitude, with that of commercial rangeland consistently 5% higher than that of communal rangeland. Notwithstanding sampling problems of accurate relocation of his plots and adequately matching his subjective method of data collection, Acocks' data has provided an invaluable opportunity for examining vegetation change over an appropriate time scale for vegetation comprised of perennial plants.

Abstract: The semi-arid savannah environment (SASE) of sub-Saharan Africa are characterized by low erratic rainfall which result to high risk of droughts, intra-seasonal dry spells and frequent food insecurity. The main occupation is subsistence small-scale rainfed agriculture and livestock production, which normally compete for the limited water resources. The main challenges to improving the livelihoods of the small-scale farmers are how to upgrade rainfed agriculture to improve rural livelihoods and conserve nature, and upgrade upstream landuse in balance with water needs for human and ecosystems downstream. There is an increased interest in opportunities of improving rainfed agriculture through adoption of rainwater harvesting (RWH) technologies. However, there is inadequate knowledge on hydrological impacts and limits of up-scaling rainwater harvesting at a river basin scale. Rainwater harvesting has a potential of addressing spatial and temporal water scarcity for domestic, crop production, livestock development, environmental management and overall water resources management is SASE. However, this potential has not been exploited despite the occurrence of persistent low agricultural production and food shortage in sub-Saharan Africa. The need to quantify this perceived potential and related hydrological impacts on a river basin led to the on-going research project titled "hydrological impacts of up-scaling RWH on upper Ewaso Ng'iro river basin water resources management". It is envisaged that the study will contribute to formulation of sustainable RWH up-scaling strategies to enhance food production and hydro-ecological balance in semi-arid savannahs of Africa. This paper presents the preliminary findings of the study mainly focusing on assessment of the potential of RWH technologies for improving food and water availability especially in semi-arid regions of eastern Africa. This was achieved by evaluating six RWH case studies selected from four countries (Ethiopia, Kenya, Tanzania and Uganda). Despite the success of a number of RWH systems, the rate of adoption is still low, hence making their impacts marginal. Nevertheless, there is a knowledge gap on the limits of up-scaling RWH in a river basin, which the other components of the study will address. The assessment of the hydrological impact of up-scaling RWH technologies is expected to provide answers to the question, what is the limit of up-scaling rainwater harvesting in a river basin?

Abstract: Gullied and ungullied catchments in four areas of deeply weathered saprolite in the Middle Veld of Swaziland can be successfully separated (p<0.01) using discriminant analysis based on area and slope of their basin heads. The discriminant scores for the catchments indicate that those on the Manzini land system differ in their behaviour from those on the Lobamba land system. No differences exist within each land system with respect to land use when the basins are classified as arable, rangeland or mixed. The discriminant functions indicate that gullies on the Lobamba land system have developed by Hortonian overland flow whereas those on the Manzini land system should be attributed to subsurface processes. Since no evidence exists for subsurface activity, it is suggested that gullying on the Manzini land system has been more active and, though initiated by overland flow, has developed to a stage where seepage at the base of the saprolite is now the main process. Erosion control measures should be based on dense ground vegetation to reduce flow velocity on the Lobamba land system and deep-rooted vegetation with high evapotranspiration rates to reduce flow volumes on the Manzini land system.

Abstract:

Abstract: Fast growth tree plantations and secondary forests are considered highly efficient carbon sinks. In northwest Patagonia, more than 2 million ha of rangelands are suitable for forestry, and tree plantation or native forest restoration could largely contribute to climate change mitigation. The commonest baseline is the heavily grazed gramineous steppe of Festuca pallescens (St. Yves) Parodi. To assess the carbon sequestration potential of ponderosa pine (Pinus ponderosa (Dougl.) Laws) plantations and native cypress (Austrocedrus chilensis (Don) Flor. et Boutl.), individual above and below ground biomass models were developed, and scaled to stand level in forests between 600 and 1500 annual rainfall. To calculate the carbon sequestration baseline, the pasture biomass was simulated. Also, soil carbon at two depths was assessed in paired pine-cypress-pasture sample plots, the same as the litter carbon content of both forest types. Individual stem, foliage, branch and root log linear equations adjusted for pine and cypress trees presented similar slopes (P>0.05), although some differed in the elevations. Biomass carbon was 52.3 Mg ha-1 (S.D.=30.6) for pine stands and 73.2 Mg ha-1 (S.D.=95.4) for cypress forests, given stand volumes of 148.1 and 168.4 m3 ha-1, respectively. Soil carbon (litter included) was 86.3 Mg ha-1 (S.D.=46.5) for pine stands and 116.5 Mg ha-1 (S.D.=38.5) for cypress. Root/shoot ratio was 19.5 and 11.4%, respectively. The low r/s value for cypress may account for differences in nutrient cycling and water uptake potential. At stand level, differences in foliage, taproot and soil carbon compartments were highly significative (P<0.01) between both forest types. In pine stands, both biomass and soil carbon were highly explained by the rainfall gradient (r2=0.94). Nevertheless, such a relationship was not found for cypress, possibly due to stand and soil disturbances in sample plots. The carbon baseline estimated in pasture biomass, including litter, was 2.6 Mg ha-1 (S.D.=0.8). Since no differences in soil carbon were found between pasture and both forest types, additionality should be accounted only by biomass. However, the replacement of pasture by pine plantations may decrease the soil carbon storage, at least during the first years. On the other hand, the soil may be a more relevant compartment of sequestered carbon in cypress forests, and if pine plantation replaces cypress forests, soil carbon losses could cause a negative balance.

Abstract: The dynamics of nutrients was compared in a clonal Eucalyptus plantation and in a native savanna in Congo. This paper focuses on changes in the precipitation chemistry during the transfer of solutions aboveground in both ecosystems. Average rainfall during the rainy and the dry seasons was 151 and 7 mm per month, respectively. Chemical analyses performed monthly over a 3-year period showed that the concentration of all the elements in rainfall increased sharply during the dry season. Wet depositions were dominated by the cations Na+, N-NH4+, H+ and the anions Cl-, S-SO42-, N-NO3- and amounts of dry depositions of Ca2+, Cl- and H+ were highly variable depending on the characteristics of the collector. Throughfall and stemflow were enriched in most of the elements, but N foliar uptake was observed in both stands. Clear differences in behaviour between the savanna and the Eucalyptus stand were evidenced. Whereas the enrichment of solutions through the foliage mainly made up of dry depositions in the plantation, foliar leaching processes were much greater in the savanna, particularly for K+, Mg2+ and P-H2PO4-. Stemflow solutions followed the same pattern as throughfall solutions. They were greatly enriched for most elements but N uptake also occurred. The low availability of K+ in the soil might account for the particularly low levels of foliar leaching of this element in the Eucalyptus stand compared to values reported for most forest ecosystems. The time course of concentrations of elements in rainfall, throughfall and stemflow provided relevant data to distinguish external inputs from foliar leaching in the enrichment of solutions through both stands. This qualitative information will be helpful to establish input-output budgets of nutrients in these ecosystems.

Abstract: Abstract Aims To identify approaches to improve our understanding of, and predictive capability for, mixed tree�grass systems. Elucidation of the interactions, dynamics and determinants, and identification of robust generalizations that can be broadly applied to tree�grass systems would benefit ecological theory, modelling and land management. Methods A series of workshops brought together scientific expertise to review theory, data availability, modelling approaches and key questions. Location Ecosystems characterized by mixtures of herbaceous and woody plant life-forms, often termed �savannas�, range from open grasslands with few woody plants, to woodlands or forests with a grass layer. These ecosystems represent a substantial portion of the terrestrial biosphere, an important wildlife habitat, and a major resource for provision of livestock, fuel wood and other products. Results Although many concepts and principles developed for grassland and forest systems are relevant to these dual life-form communities, the novel, complex, nonlinear behaviour of mixed tree�grass systems cannot be accounted for by simply studying or modelling woody and herbaceous components independently. A more robust understanding requires addressing three fundamental conundrums: (1) The �treeness� conundrum. What controls the relative abundance of woody and herbaceous plants for a given set of conditions at given site? (2) The coexistence conundrum. How do the life-forms interact with each other? Is a given woody�herbaceous ratio dynamically stable and persistent under a particular set of conditions? (3) The net primary productivity (NPP) conundrum. How does NPP of the woody vegetation, the herbaceous vegetation, and the total ecosystem (woody + herbaceous) change with changes in the tree�grass ratio? Tests of the theory and conceptual models of determinants of mixed woody�herbaceous systems have been largely site- or region-specific and have seldom been broadly or quantitatively evaluated. Cross-site syntheses based on data and modelling are required to address the conundrums and identify emerging patterns, yet, there are very few data sets for which either biomass or NPP have been quantified for both the woody and the herbaceous components of tree�grass systems. Furthermore, there are few cross-site comparisons spanning the diverse array of woody�herbaceous mixtures. Hence, initial synthesis studies should focus on compiling and standardizing a global data base which could be (1) explored to ascertain if robust generalizations and consistent patterns exist; and (2) used to evaluate the performance of savanna simulation models over a range of woody�herbaceous mixtures. Savanna structure and productivity are the result of complex and dynamic interactions between climate, soils and disturbances, notably fire and herbivory. Such factors are difficult to isolate or experimentally manipulate in order to evaluate their impacts at spatial and temporal scales appropriate for assessing ecosystem dynamics. These factors can, however, be evaluated with simulation models. Existing savanna models vary markedly with respect to their conceptual approach, their data requirements and the extent to which they incorporate mechanistic processes. Model intercomparisons can elucidate those approaches most suitable for various research questions and management applications. Conclusion Theoretical and conceptual advances could be achieved by considering a broad continuum of grass�shrub�tree combinations using data meta-analysis techniques and modelling.

Abstract: This paper tests the feasibility of applying a technique developed by Piperno and Pearsall (Am. Antiquity 49 (1984) 361; Phytolith Analysis: An Archaelolgical and Geological Perspective, 1988, Academic Press: San Diego; Paleoethnobotany, 2000, Academic Press: San Diego) based on size and three-dimensional morphology criteria of cross-shaped phytoliths to identify maize in a previously unexplored region outside of the Neotropics; the grasslands of southeastern Uruguay. Because the area is dominated by subtropical Panicoid grasses that produce abundant cross-shaped phytoliths, intensive studies of the regional Panicoid grasses are needed to ensure that no wild taxa have phytoliths that are potentially confusable with maize. With this in mind, I carried out analysis of cross-shaped phytoliths in 35 Panicoid, 5 Oryzoid and 1 Bambusoid grasses, as well as on nine modern soil samples that belong to the most representative vegetation formations of the area. This study demonstrates that an application of multivariate (linear discriminant function) analysis together with qualitative and other assessments of cross-shaped phytolith assemblages as originally described by Piperno and Pearsall can be successfully used to distinguish the presence of maize in the grasslands of southeastern Uruguay. The technique provides a useful tool to trace the dispersal of maize into the southern cone of South America.

Abstract: The development of vegetation cover is one of the primary indicators for land degradation, stability, or regeneration in regions threatened by overgrazing. This paper addresses the problem how spatially explicit information about degradation processes in European Mediterranean rangelands can be derived from long time series of satellite data. The selected test site in central Crete, Greece, is considered to be representative for the highly heterogeneous character of such landscapes. The monitoring approach comprises the time period between 1977 and 1996, covered by nine Landsat TM and four Landsat MSS images. Special emphasis has hence been put on the evaluation of potentials and drawbacks when coupling Landsat TM and MSS based results. The data sets were geometrically and radiometrically pre-processed in a rigorous fashion, followed by a linear spectral unmixing approach and a time series analysis of vegetation fraction images. Based on the resulting map, the spatio-temporal patterns of vegetation cover changes are explained. Even a test site such as central Crete, with its limited spatial extend, exhibits heterogeneous patterns of change, supporting the hypothesis that long time series of EOS data from Landsat-like sensors are mandatory to identify the relevant changes at landscape level.

Abstract: Abstract General models of rangeland degradation suggest that soil and nutrients are lost and conversion of rainfall into primary productivity is diminished. These models are supported by studies on [`]non-resilient' landscapes but have not been tested on [`]robust' or [`]resilient' landscapes. Results are presented as one large example (2000 ha) of a resilient landscape typical of the arid shrubland of Western Australia. The experiment was necessarily replicated in time not space, which limits confident extrapolation of the results to other areas. Over twelve years, when rainfall was mostly average or below-average, rainfall-use efficiency was 29% greater and net primary productivity 15% greater on a non-degraded landscape than on a similar degraded landscape where there were far fewer shrubs. Although our data conform with the general model of landscape degradation, that is degraded landscapes are less efficient in converting rainfall into biomass, in four of the 12 years, rainfall-use efficiency was similar to or greater on the degraded landscape than on the non-degraded landscape. There was increased production from ephemeral species on the degraded landscape, particularly in years of higher rainfall, and primary productivity became more variable from season to season. These responses are reported to characterize resilient landscapes. These data suggest that both resilient and non-resilient landscapes conform to a similar general model of landscape degradation. That is, averaged over time, primary productivity and rainfall-use efficiency are still reduced on degraded resilient landscapes. Allgemeine Modelle über "Rangeland" Degradierungsprozesse weisen darauf hin, dass Mutterboden und Nährstoffe verloren gehen und dass daher die Nutzungseffizienz von Niederschlägen für die primäre Produktivität geringer ist. Wenngleich Ergebnisse aus Studien in fragilen oder "nicht-resilienten" Landschaftsformen diese Modelle unterstützen, so wurden aber noch keine Untersuchungen in robusten oder "resilienten" Landschaftsformen durchgeführt. In der vorliegenden Studie wurde eine flächenmä�ig gro�e (2000 ha) "resiliente" Landschaftsform untersucht, die sich in ein durch �berweidung degradiertes und ein nicht-degradiertes Untersuchungsgebiet aufteilen lie� und die typisch ist für das aride Buschland von West Australien. Notgedrungen wurde das Experiment zeitlich aber nicht räumlich repliziert, was eine Extrapolation der Ergebnisse auf andere Gegenden erschwert. In einem Untersuchungszeitraum von zwölf Jahren, in dem die Niederschlagsmenge durch-schnittlich oder unterdurchschnittlich war, konnte in dem nicht-degradierten Untersuchungsgebiet eine 29% höhere Niederschlags-Nutzungseffizienz und eine 15% höhere primäre Produktivität festgestellt werden, im Vergleich zu dem degradierten Untersuchungsgebiet, welches weniger Sträucher aufwies. Wenngleich diese Ergbnisse mit den herkömmlichen Modellen der Landschafts-Degradierung konform gehen, nämlich dass degradierte Landschaftsformen Niederschläge weniger effizient in Biomasse umwandeln können, so war in vier der zwölf Untersuchungsjahre die Niederschlags-Nutzungseffizienz ähnlich oder grö�er auf der degradierten Fläche im Vergleich zur nicht-degradierten Fläche. Auf der degradierten Fläche wurde eine vermehrte Produktion von ephemeren Pflanzen festgestellt, vor allem in Jahren mit höheren Niederschlägen, und die primäre Produktivität variierte in zunehmendem Ma�e von Saison zu Saison. Dies sind eigentlich Charakteristika für "resiliente" Landschaften. Diese Ergebnisse weisen darauf hin, dass sich sowohl "resiliente" als auch "nicht-resiliente" Landschaftsformen in ein generelles Modell der Landschafts-Degradierung einordnen lassen: primäre Produktivität und Niederschlags-Nutzungseffizienz sind, gemittelt über die Zeit, in degradierten "resilienten" Landschaften reduziert.

Abstract: Understanding the impact of fire on the demography of savanna trees and shrubs is necessary for understanding human impacts in tropical savannas. In a replicated experiment, we studied the impact of fire and vegetation cover on survival and growth of two subshrubs (Periandra mediterranea and Protium ovatum), two shrubs (Miconia albicans and Rourea induta) and three trees (Myrsine guianensis, Piptocarpha rotundifolia and Roupala montana) of the Brazilian cerrado savannas. Burning increased complete mortality (i.e. death of the individual) of five of the seven species, but primarily among individuals with stem diameters <4 mm. Stem mortality (i.e. topkill) was much more prevalent, primarily affecting individuals with stem diameter <32 mm, though all species experienced some topkill in even the largest size classes. Fires of higher intensity (flame length >2 m) caused greater mortality and topkill than fires of lower intensity (flame length <2 m). Pre-burn vegetation density had little effect on survival or resprout size, but did affect subsequent growth rates. Four species had greater growth rates in open sites, whereas only one species had greater growth rates in dense sites. For the three tree species and one shrub, resprouting individuals did not reach the minimum reproductive size within 1 year of burning, while the other shrub and the two subshrubs were able to reach reproductive size during this time, indicating that growth form largely determines the population response to frequent burning.

Abstract: Ground-based data on total phytomass were collected in 1998 and 1999 from four sampling domains, each nearly 1000 km2, within the arid shrubland of Western Australia. These data were used in models relating rainfall and landscape characteristics to total phytomass to provide landscape-scale estimates of total phytomass and rainfall-use efficiency for 1992-1999 (referred to as RUEP). These modelled estimates were compared with remotely sensed estimates of total phytomass (I-NDVI) and rainfall-use efficiency (I-NDVI/annual rainfall; referred to as RUEN) using data from NOAA satellites. There was good agreement between ground-based and remotely sensed estimates of total phytomass but less agreement between estimates of rainfall-use efficiency. Partitioning the landscape on the basis of landscape resilience did not improve the amount of variance accounted for in RUEP or RUEN and there were conflicting relationships between landscape-scale indicators of landscape function and RUEN. There was, however, evidence to suggest that temporal change in RUEN may provide a useful broad-scale indicator of landscape degradation or recovery over decadal time intervals. Recommendations are made for broad-scale application of this indicator based on temporal trends in RUEN.

Abstract: We examined the relationship between biopedturbation (animal caused soil disturbance) and several vegetation and soil-based indicators of rangeland condition to evaluate the effects of desertification on animal soil disturbance. The area, volume, and abundance of various biopedturbation types were assessed at 117 sites in south-central New Mexico where vegetative cover and composition had been measured previously. There were significant relationships between biopedturbation and selected rangeland condition indicators. Increasing percentages of grass cover were positively associated with increasing total area of biopedturbation. Increasing percentages of shrub cover and mean bare patch size were negatively associated with total biopedturbation area. Biopedturbation area and volume were related to indicators of rangeland condition and percent shrub cover best predicts the area of soil disturbed by animals. This relationship, however, cannot reliably predict total biopedturbation area or the area of soil disturbance types.

Abstract: Apart from a decrease in total perennial plant cover, degradation of North-African arid lands is not easy to qualify. Yet, simple and comprehensive yardsticks are necessary to assess degradation. We assigned components of competitive ability (C), stress tolerance (S) and ruderality (R) to 15 common perennials of Presaharian Tunisia. We used for that purpose phyto-ecological studies, data about life-form, grazing value and demography and circumstantial data. Assigning CRS-strategies to these species improves understanding of vegetation change under increased anthropic influence, helps to conceive experiments to confirm underlying hypotheses and sheds another light on the controversy about restoring arid lands.

Abstract: Questions as to whether public investment in international agricultural research is a [`]Good Thing' or not may best be addressed using two arguments: (1) justifications based on whether or not past investments have yielded substantial benefits to societies and the resource-poor; and (2) that future investments need to be made as effectively and efficiently as possible, which means they must be targeted as closely as possible. A major component of any impact assessment framework that aspires to comprehensiveness is information on the location of different agricultural systems and pertinent characteristics of the resource-poor who operate them. Given the importance of livestock to the diets and incomes of poor farming households, and the predicted increase in demand for livestock products throughout the developing world over the next few decades, understanding how livestock fit into these systems, and how these systems may evolve in the future, is critical. This is especially true in Africa, where approximately 27% (162 million people) of the world's poor livestock keepers live. In this paper, we further develop a global livestock production system classification put forward by Seré and Steinfeld in 1996. These livestock systems fall into four categories: landless systems, livestock only/rangeland-based systems (areas with minimal cropping), mixed rainfed systems (mostly rainfed cropping combined with livestock) and mixed irrigated systems (a significant proportion of cropping uses irrigation and is interspersed with livestock). We then describe a method for mapping the classification, based on agro-climatology (length of growing period), land cover, and human population density. We conclude with a discussion of how the maps could be refined, and indicate their potential use in a range of different policy and research and development applications.

Abstract: Plant materials that can replace costly inorganic fertilizers as phosphorus (P) sources are needed in smallholder farming systems in tropical Africa, where P is often yield-limiting. The objective of this study was to determine the relationship between the biochemical composition (quality) of plant materials, described in terms of total P, total nitrogen (N), lignin (LIG), and soluble phenolics (Pp), and soil P availability (Pav) under laboratory incubation conditions. The materials were ground and added to the soil at a rate equivalent to 10 Mg ha-1 (DM) and the samples (including a control soil) were kept at 50% field moisture capacity and 25 °C. The anion exchange resin method was used to extract solution P periodically. Because P added was not balanced among the treatments, Pav was expressed as percentage of total P of plant material (i.e. Pav=100�[(Pav amendedsoil-Pav controlsoil)/totalPadded]. Some treatments showed net P release and others showed net P uptake. The pattern of Pav was viewed in three phases: (i) an initial rapid P release from the sparingly soluble inorganic P fraction of the plant materials, (ii) a subsequent phase when P in solution comes from both soluble P and mineralization of plant materials, and (iii) a last phase when P in solution is influenced by its equilibrium with P sorption processes. Total P was the best predictor of Pav with r2 (P<=0.05) ranging from 0.50 to 0.77. Predictive functions were developed to determine the critical quality levels for net P release and net P uptake. The critical quality levels ranged from 2.0 to 2.7 g kg-1 for total P; 156:1 to 252:1 for C/P ratio; and 7:1 to 14:1 for N/P ratio. Among the materials tested, Tithonia diversifolia and Croton megalocarpus which contained total P >3.0 g kg-1 of total dry weight were identified as having the potential to release adequate P to replenish solution P for crop uptake.

Abstract: This paper describes a process-based metapopulation dynamics and phenology model of prickly acacia, Acacia nilotica, an invasive alien species in Australia. The model, SPAnDX, describes the interactions between riparian and upland sub-populations of A. nilotica within livestock paddocks, including the effects of extrinsic factors such as temperature, soil moisture availability and atmospheric concentrations of carbon dioxide. The model includes the effects of management events such as changing the livestock species or stocking rate, applying fire, and herbicide application. The predicted population behaviour of A. nilotica was sensitive to climate. Using 35 years daily weather datasets for five representative sites spanning the range of conditions that A. nilotica is found in Australia, the model predicted biomass levels that closely accord with expected values at each site. SPAnDX can be used as a decision-support tool in integrated weed management, and to explore the sensitivity of cultural management practices to climate change throughout the range of A. nilotica. The cohort-based DYMEX modelling package used to build and run SPAnDX provided several advantages over more traditional population modelling approaches (e.g. an appropriate specific formalism (discrete time, cohort-based, process-oriented), user-friendly graphical environment, extensible library of reusable components, and useful and flexible input/output support framework).

Abstract: Biomass burning is an important ecosystem process in southern Africa, with significant implications for regional and global atmospheric chemistry and biogeochemical cycles. In this paper, representative Landsat path-row scene locations, distributed over southern Africa, were used to quantify the area burned and to understand the coupled role of the timing and the extent of burning on regional emissions. The total area burned and the scar size distribution were found to vary between semi-arid and humid scenes and dry and average rainfall years. Analysis of images from the start and end of the burning season resulted in a modest underestimate of the annual area burned, as compared to using a monthly time-series approach. However, at the regional level the start/end method is likely to yield acceptable annual burned area estimates and total carbon dioxide estimates. On the other hand, combustion factors and emission factors vary sufficiently during the burning season to result in large errors in emission estimates of products of incomplete combustion, when using the start/end method. This study indicates that in southern Africa, the timing in addition to the extent of burning must be considered and that time-series satellite burned area products are needed to quantify pyrogenic emissions accurately.

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Abstract: Pikas (Ochotona spp.) are burrowing herbivorous mammals believed to play a keystone role in determining the biodiversity of steppe ecosystems. Impacts of domestic livestock grazing on the distribution and abundance of the Daurian pika Ochotona daurica were investigated in eastern Mongolia where the species is widespread and abundant. Effects of pikas on plant species richness and vegetation coverage were examined at different distances from burrow systems. Daurian pikas were nearly absent from severely grazed study sites, and incidence of the species increased with decreasing grazing intensity. The number of occupied burrow systems and usage of burrows was higher in sites with lower grazing pressure. Plant species richness and ground cover was higher at 3&ndash;12 m from the burrow systems than directly over burrows, suggesting that the effect of Daurian pikas is limited to the burrow system. Contradictory to previous studies on grassland pikas, this study indicates that Daurian pikas suffer from overgrazing and that their impact on grassland is only light.

Abstract: The study aims to examine the origin and development of land degradation with particular emphasis on badland and gully systems in the Sneeuberg uplands of the Great Karoo. This is an area of semiarid extensive stock farming where land degradation in the form of rill and gully erosion has accompanied the replacement of grassland by shrub vegetation. Species diversity has declined and ground cover has been reduced, leading to a positive feedback loop which exacerbates the degradation. Many foot slopes developed in shales, clays and colluvium have extensive, incipient badland development with closely spaced gullying up to 1.5 m deep. In valley-bottom and valley-side depression locations gullies up to 8 m deep have developed, usually cut to bedrock through valley fills of mainly Holocene colluvium. Both badlands and gullies appear to have developed since European settlement and to be part of the same hydrological system with extensive areas of bare ground (badlands) feeding water to incising gullies. Experiments using simulated rainfall throw some light on current processes. Badland areas are active under high-frequency, low-magnitude rainfall events. Major gullies are likely to be the result of occasional, high-magnitude events, but these have not been observed. Overgrazing in the past is the most likely cause of the degradation.

Abstract: In the Sahel and the Kalahari, the growth in groundwater extraction via simple wells and boreholes is contributing to an increased use of dryland natural resources, to competition for resources, and to environmental changes. Livestock production systems in particular have expanded through the utilisation of groundwater in areas devoid of perennial surface water sources. Environmental changes are most marked in vegetation systems that were utilised ephemerally and opportunistically in years of good rains prior to the all-year-round exploitation facilitated by groundwater. The nature of vegetation changes, notably biodiversity reduction and changed relationships between annual and perennial grasses and bush cover, is considered, including whether such changes represent environmental degradation and whether they are permanent. Process studies indicate that bush encroachment, a particularly marked form of vegetation change, is reversible at decadal to century time-scales, in the context of the natural dynamism of dryland ecosystems. At shorter time-scales such changes can even open up new resource opportunities that may relieve pressures on critical grazing resources at times of environmental stress. Ultimately however, available data on water availability suggest that the rate of groundwater extraction is probably unsustainable, and this may provide the ultimate limit on the wider environmental impacts that borehole-centred livestock systems have on the environment.

Abstract: This chapter describes relationships between environmental stress and the reaction of plants thereupon. Plants might react to environmental stress on various levels: on the biochemical, cellular, or morphological scale, and at species or population level. The characteristics of organisms change with their size (allometric relationships), with their life history (and related allocation strategies) and with their functional evolution. We discuss in this chapter, what kind of information may be derived from the composition of the vegetation (species diversity and species abundance). We provide insights in the effects of environmental stress on biodiversity., e.g. shifts in communities, the loss of species and appearance of new species. These insight may contribute to the validation of environmental standards. Another aspect we have dealt with is the use of plants to track climate and land-use changes in history. The use of plants as a bioaccumulative indicator is not discussed. When using a bioindicator, it is particularly important to state clearly which stress factor it is supposed to be sensitive for. It is shown in this chapter, that the sensitivity of plants for, e.g., heavy metals is dependent on the combination of morphological, anatomical and phenological characteristics of the plant. Evergreen plants are far more sensitive than early spring green plants, while shrubs are more sensitive than trees and obligate annuals (therophytes) are more sensitive than facultative annuals. Dependent on the character states, plants, or plant parts, may be, and are, used as climatic indicators, e.g., life forms and leaf anatomy in relation to temperature, rainfall and atmospheric CO2, or as reliable ecotoxicological tools (rootlet growth in testing solutions; and as time proxies (e.g. tree rings). The composition of plant communities can deliver a lot of information about environmental conditions. Further the implications of the so-called Ellenberg approach are analysed. Changes in vegetation over time indicate changes in climate patterns, as the main biotic response to climate change is migration, to track optimal conditions for growth. The type of photosynthetic pathways (C3 versus C4 photosynthesis) and leaf anatomy of plants as indicators for climatic changes is discussed and coupled with atmospheric teleconnections like El Niño and its antagonist La Niña. A very interesting way of bioindication by plants is used by palynologists. Their use of plant remains as proxies for vegetation history and human influence provides information about the development of the present society, also from periods where there were no written sources. They show us what the world looked like in historic and pre-historic era. This latter work can be seen as assessments of early human impacts on the environment.

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Abstract: The contribution deals with the contextual design of spatial data for regional development and land management purposes. Further development of information technologies, image processing techniques and contextual knowledge-based databases, together with the geographical networks environment, will provide quite new and considerably wider possibilities of using GIS. GIS architecture is open to incorporate new requirements of knowledge-based analysis and modelling, namely in connection with web designed spatial databases. The paper describes the role of remote sensing data and contextual modelling for the context-oriented geo-information and tries to provide a framework for the object hierarchy of classes and propose the ways of the structure and behaviour modelling.

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Abstract: The following dissertation sets out to investigate the decline of agriculture in Mission location at Butterworth, Transkei, using the Rehabilitation Scheme as a benchmark. The scheme was introduced in 1945 to combat soil erosion and improve agriculture in the African reserve areas, as the South African government claimed. The dissertation argues that this claim by the government served to mask the real intentions behind the scheme namely, to regiment the migrant labour system by depriving as many Africans as possible of productive land so that they were unable to fully subsist by means of agriculture. This is further shown by analysing the impact of the Rehabilitation scheme in Mission location in which a substantial number of people lost arable land as a result of the implementation of the scheme in 1945. These people were consequently denied the wherewithal to subsist by agriculture. Moreover, the efforts of the government resulted to a modernisation of agriculture by making it more cash-based- for example through the introduction of fencing, the need for tractors as a result of a decline in stock numbers (in part as a result of stock culling). Most people could hardly afford this type of agriculture and were consequently forced off the land. The dissertation concludes that indeed the decline of agriculture in Mission location can be linked to the changing agricultural and land-holding practices brought about by the government- especially the introduction of the Rehabilitation scheme.

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