Abstract: A state-of-the-art review is presented concerning the transport of nutrients (N and P), oxygen demanding compounds (BOD and COD), indicator organisms and pathogens in runoff from land areas receiving animal wastes. Three different land areas are considered: pastures and rangelands, land application sites, and feedlots. For land application sites, results of a linear regression analysis indicated highly significant correlations between constituent (N or P) loading rate and its concentration in runoff water, and also between constituent loading rate and its mass yield rate. Field plots receiving manure during winter and spring, and subject to snowmelt runoff followed a different relationship compared to those receiving applications during summer and fall, and not subject to snowmelt runoff. Effects of various factors, such as time and method of application, soil and cropping management practices, in relation to transport of nutrients are discussed. The limitations of the available data are discussed in terms of identifying future research needs. The greatest need appears to be that of relating the limited data on small plots to larger watersheds, and edge-of-field losses to receiving waters.
Abstract: The prediction of land erosion rates under different types of land use is difficult because of the large number of variables involved. This paper attempts to isolate the most important characteristics of land contributing to its crodibility, and then describes the geomorphological approach used to assess and map land erosion potential in the Kamberg area of the Drakensberg mountains, South Africa. Emphasis is placed on the fact that land erosion potential varies with land use type, and recreational land use only is considered. The terrain at Kamberg could be divided into four sections, each displaying a degree of internal homogeneity in land erosion potential, yet distinguishable from its neighbours through geomorphological and topographic characteristics. Inherent subjectivity in terrain evaluation techniques, and lack of threshold values for variables concerned constitute the main weaknesses of the method used, and because of this, such work should be undertaken only by an experienced field geomorphologist.
Abstract: Modeling the combined hydrological and energy balances of Paleolake Chad and its drainage basin yields an estimate of at least 650 mm/yr for annual precipitation during portions of the early Holocene (10,000 to 5000 yr B.P.); the current rainfall in Chad Basin is 350 mm/yr. Two versions of the model are developed. The first version is one in which precipitation and lake area are linearly related. This version requires specification first of the area, net radiation, and Bowen ratio of the lake and second of the paleovegetation, net radiation, and Bowen ratio of the surrounding basin. In the second version of the model the ralationship between precipitation and lake area is nonlinear because the runoff ratio and Bowen ratio of the basin are made functions of precipitation. As the lake increases in area in response to increased precipitation, this version of the model allows for further increases in runoff (from the basin into the lake) as the vegetation changes from steppe to savanna and swamp. This nonlinear process may provide a partial explanation for the expansive paleolakes of the early Holocene. The results derived from both models are in good agreement with previously derived estimates of precipitation for North Africa during the early Holocene.
Abstract: A general description and a map of the agricultural systems in Ethiopia have previously been published, but the approach and methodology used to arrive at this classification was not adequately described. The two dominant agricultural systems in Ethiopua are the mixed agriculture of the humid and sub-humid highlands and pastoralism in the arid and semi-arid lowlands covering 40 and 60% of the country respectively. These divergent systems are clearly a result of agro-climatic differences and their sub-systems indicate, in part, the range of climatic situations. The approach used to distinguish and describe the agricultural systems in Ethiopia is described and two examples are provided to illustrate the process; one being a synthesis of present land use systems in the Ethiopian Highlands, and the other, a land capability survey for a range lands development project in the southeastern Ethiopian Lowlands.
Abstract: An examination of sediment from piston cores and 3.5-kHz seismic reflection profiles from the northern Cape Basin and southern Angola Basin reveal a contrasting history of depositional processes in these adjacent basins. Pleistocene sedimentation in the southern Angola Basin was characterized by extensive deposition of turbidites and hemipelagic sediments derived primarily from the discharge of the Kunene River. Slumping of sediments and highly mobile debris flows have also contributed in the basinward transport of sediments in this region. In contrast, the northern Cape Basin can be characterized as a "starved" basin. Because of the low coastal rainfall and extremely low level of river discharge, the marine sediments along this margin are essentially pelagic in origin. Slumps and slides have disrupted portions of the continental margin but the morphology of the slope is very smooth in contrast to the margin north of the Walvis Ridge where canyon cutting has played a major role. The low sedimentation rates in the northern Cape Basin in conjunction with a moderate to strong bottom-water circulation has resulted in an extensive erosional zone along the lower continental rise off southwest Africa. The effects of a changing climate (interglacial--glacial) on marine productivity and sedimentation are documented by the faunal and isotopic record in a piston core on the continental rise south of the Walvis Ridge.
Abstract: Water-harvesting techniques can increase the useable water supplies of arid and semiarid areas. A relatively new water-harvesting treatment is the application of paraffin wax to soils to create a water-repellent catchment surface. The first two such catchments were installed at the Granite Reef test site in 1972 by applying ground paraffin wax (0.7 kg/m2 average rate) atop smoothed, rain-compacted soils. Solar energy melted the wax into the soil. The catchments are still operational after 7 years of natural weathering. Average runoff efficiency (yearly runoff/yearly rainfall) for the two catchments averaged 87% for the 7 years. Year 7 averages were 85%, i.e., only 2% less than the 7-year average. Also, the 7-year average runoff efficiency of the two catchments was only 10% less than that of a plastic membrane, but was more than four times greater than that of a simple, cleared and smoothed soil surface and nearly six times greater than that of a small untreated, natural desert watershed. Several operational wax-treated catchments have been built to supply water to livestock on arid rangeland. Ranchers are pleased with them -- equating them to permanent springs. Both laboratory and field tests indicated that the wax treatment is most successful on sandy soils containing less then 20-25% clay plus fine silt.
Abstract: The development of reliable paleoclimatic maps at a global scale requires data at the following three levels of analysis: (1) well-recorded observations of evenly positioned, well-dated geological evidence (Level I), (2) paleoclimatic estimates derived from this evidence by well-defined quantitative repeatable methods (Level II), and (3) maps synthesizing the estimates from several independent sources of geological evidence (Level III). Our paper describes much of the currently available paleoclimatic data from unglaciated terrestrial areas at ca. 18,000 yr B.P. and illustrates the quantity and quality of the data at both the Level I and the Level II stages of analysis. Although the scarcity of well-dated evidence for this time period precluded any major Level III syntheses of the information, comparisons were drawn where possible between the geological evidence and the climatic conditions simulated by general-circulation model experiments of Gates, 1976a and Gates, 1976b and Manabe and Hahn (1977). Of the more than 320 sites with data from 18,000 yr B.P., only 65 are well-dated with bracketing dates within the interval of 23,000 to 13,000 yr B.P., whereas about 100 are undated or poorly dated. We concentrated our survey on palynological and paleobotanical evidence and also thoroughly reviewed the evidence for water levels in lakes at 18,000 yr B.P. In areas with few of these sources of evidence, data on former snowlines, periglacial features, and eolian deposits were included, but the survey of these data is far from complete. Maps of the assembled data reveal the consistency of the paleoclimatic estimates in "data-rich" areas and also show which areas required additional information. The maps show that conditions were colder than present at 18,000 yr B.P. for all sites with temperature estimates. Estimated temperature depressions varied from ca. 1° to 12°C or more, depending on the location of the sample, the type of geological evidence, and the method of temperature estimation. Interpreted hydrological conditions were more variable spatially than the temperature estimates. The southwestern U.S. was moister than present, whereas the southeast may have been drier. Europe and the northern Mediterranean across to Afghanistan were drier than present, but northwest Africa was wetter. Australia was mainly drier than present, but several sites there as well as in Africa show significant climatic changes between 21,000 and 16,000 yr B.P. This latter evidence suggests that considerable variability may have occurred during the several thousand-year period centered on 18,000 yr B.P. Accurate time control is therefore required for the geological data used to study the climate dynamics of 18,000 yr ago. Large portions of South America and Asia as well as significant portions of the other continents lack the data base, or at least the well-dated base, required to define the 18,000 yr B.P. climate. In the few areas where comparisons were made with the Ice Age climates simulated by general-circulation models, general agreement existed between the geological evidence and the model simulations. Many critical comparisons were thwarted, however, by the lack of model simulations for all seasons at 18,000 yr B.P. Difficulty in validating precipitation anomalies in the tropics also arose because surface-albedo values, which are a vital input to the general circulation models, are estimated from the same evidence that is used to validate the results of the models.
Abstract: Summary Small dome-shaped hills are recurrent and common landforms associated with plateau surfaces in the savanna woodland landscapes, both to the north and south of the Congo Basin. They may be occupied in part by termite colonies or be moribund. Previous ideas on the relationships between termite hills and termite mounds are discussed. The evolution of the hills is discussed in the light of evidence from variious parts of Zambia. It is concluded that the interaction of mound building by termites and mound destruction by rain beat and rain wash is complicated by plant colonisation, interference and use by animals, the incidence of fire and the activities of agricultural man. These are also factors which might explain the distribution of termite hills. The apparent fossilisation of the termite hills through the development of thicket vegetation is not regarded as necessarily dependent on climate change but could be the result of other changing ecosystem factors.
Abstract: The atmospheric carbon dioxide content was monitored continuously near Pretoria for 15 months. Variations on the timescale of hours, days and seasons were observed and related to source and meteorological parameters. Seasonal variations were found to be greater inland than usually observed at near-coastal stations and are related to continental vegetation influences. Radiocarbon analyses show that fossil CO2 pollution is small at this site.
Abstract: SUMMARY Of at least 350 species so far recorded within the boundaries of the Niger Inundation Zone, no less than 108 (31%) are wholly or partially of Palaearctic origin. Five main habitats are recognized in the region: wetland, hygrophilous grassland, transition zone, non-flooded areas and aerial. The habitats, the Palaearctic migrants and their possible Ethiopian competitors are described and discussed. The annual Niger flood regime enables Palaearctic waterbirds to find suitable habitats somewhere within the region during all seasons, but most widely during the autumn and winter months of the flood recession. Non-aquatic species inhabiting flood plain grassland are scarce during the Palaearctic autumn, when the growth of vegetation reaches its maximum, becoming commoner and more diverse during the winter months. Wetland warblers of the genera Acrocephalus and Locustella have not been recorded on autumn passage. It is suggested that in some years at least, these and other trans-Saharan migrants from the West Palaearctic overfly the Sahelian latitudes of mid-West Africa. Species inhabiting the transition zone (which increases in area during years of below average rains and floods) are most in evidence at the end of the winter period and during the spring hot dry season, prior to northward trans-Saharan migration. Habitats and species encountered in the non-flooded areas are similar to those recorded in the Sahel zone elsewhere in West Africa. Aerial habitat is utilized by Common Swifts arriving en masse in early August, at the maximum development of the south-westerly monsoon airstream. Several aquatic species and the first few trans-Saharan migrants also occur during the summer rainy season. Some species (e. g. Whiskered Tern, Lesser Kestrel, Turtle Dove, Short-toed Lark and Sand Martin) are most numerous during the late winter and spring hot seasons, when conditions provided by the Inundation Zone may be more suitable for pre-migration feeding than in other parts of the Sahel zone. As yet there is virtually no information available to determine any effects that drought seasons or flood variation may have on the migrant populations.
Abstract: Studies were made, over a 3- to 8-yr. period, of mean seasonal and yearly changes in infiltration rates under various rangeland management practices within the pinyon-juniper (Pinus spp.-Juniperus spp.) type. Results of the study indicate that mean upper limits in measured infiltration rates range from a surprising 1.37-3.47 times the mean minimal rates, each mean value representing from 6-20 replications for a given sampling date. Soil biology may be important in determining seasonal trends in infiltration rates, as well as overwintering freeze-thaw activity. Suggestions are given for sampling infiltration rates.
Abstract: Changes of herbage biomass on ungrazed Biloela buffel grass swards at the Narayen Research Station were investigated in field experiments and by means of computer simulation. The daily rate of change of herbage biomass was calculated by an empiricial model consisting of two equations. The first, used when the ration of estimated actual to potential transpiration (transpiration ratio) was > 0.26, computed the daily of increase in herbage dry weight (DW) as the product of the potential net production of herbage multiplied by temperature and moisture factors, and by a factor that allowed for delayed regrowth when effective rain fell after drought. The second equation, used when the transpiration ratio was < 0.26, computed the daily loss of DW as a function of the standing weight of herbage multiplied by the same moisture factor. Transpiration was estimated with a water-balance model. The herbage model was used to simulate the biomass of Biloela buffel grass on an ungrazed field experiment on a duplex soil (similar to the solodic and eutric planosols of the [`]FAO Soil Map of the World'). The plots were mown three times a year, in spring, summer and autumn, and they received sufficient nitrogen and other nutrients for near-maximum production. The linear regression of measured on simulated DW's of herbage for the two years' data from which the values of the models' constants and functions were derived had a coefficient of determination (R2) of 0.955; two additional years' results from the same experiment were estimated with an R2 of 0.913. Using the same model but different soil constants, in another experiment at Narayen on a gradational clay soil (related to the eutric nitosols) the biomass of Biloela buffel grass was simulated with an R2 of 0.823. The model was then used with historical rainfall records to simulate the biomass of Biloela buffell grass herbage in the Narayen environment for the period 1887 to 1973. Frequencies were calculated for: (a) in the case of swards with optimum nitrogen supply -- estimated mean daily transpiration ratios, estimated daily rates of herbage production (or reduction), and estimated herbage yields from three harvests a year, and (b) in the case of swards dependent on soil nitrogen -- potential nitrogen fertilizer responses of at least 200 or 2000 kg DW ha-1 at the spring, summer and autumn harvests. The reduction in standing crop of herbage during drought, delay in regrowth after drought, evapotranspiration models, and nitrogen responses in dry climates are discussed with reference to previous results.
Abstract: One of the major diseases affecting human beings and livestock in Africa, trypanosomiasis--known in its common human form as sleeping sickness--remains resistant to general eradication, a wide belt across the middle of the continent. This is true even though the disease's carriers--several varieties of tsetse flies--and its need for an animal host is well understood. This paper sketches the history of medical, public health, and development concepts that have attempted and achieved short-term and local eradication with a variety of methods, as well as the ecological consequences of these eradication measures, some quite devastating. More ecologically-attuned approaches to development than the simple removal of the tsetse are required in the trypanosomiasis belt if resource degradation and famine are to be avoided.
Abstract: The article points out that, although the relative importance of the agricultural sector in the Arab world is declining as the importance of oil rises, it is still vital to Arab countries. Selfsufficiency in agriculture is desirable because of a possible cutoff of food imports for political reasons by the food-exporting countries. The article examines the possibilities for Arab selfsufficiency and suggests several alternative strategies.
Abstract: The goat, from a world wide view, is both hated and treasured because it survives and remains productive in areas that are seriously overgrazed and eroded. Goats are probably not the initial cause of rangeland deterioration, but they may be the primary culprit during the latter stages of destruction. Goats are presented as being different in diet selection and gastrointestinal physiology from other domestic animals (cattle and sheep) and similar to deer. These differences offer explanations of why the goat's elevated requirements can be satisfied under environmental conditions unsatisfactory for other animals. Some experimental evidence indicates that the goat has greater digestive capacity; however, this advantage is likely only in certain breeds or strains having definable anatomical dimensions and is not a characteristic of the entire goat population. Experimental evidence suggests that the dairy goat does not hold a distinct advantage in efficiency of milk production over the highly developed dairy cow; however, it is likely that under many circumstances in the world, milk can be produced more efficiently from goats than from cattle due to resources available and adaptability of the animals.
Abstract: The dating of the Stone Age sequence in southern Africa has been considerably revised over the last decade, and one of the anomalies which has resulted is that the Middle Stone Age, now dated to beyond 30,000 B.P., does not immediately precede the Later Stone Age sensu stricto. The excavation and analysis of occupation horizons dating between the most recent Middle Stone Age assemblages and the Holocene is therefore of particular interest. Nelson Bay Cave, situated on the southern coast of South Africa, contains deposits which partly fill the "gap" between the Middle and Later Stone Ages, and the occupation horizons dating between about 18,000 and 5000 years ago are described in this paper. Changes in the habitat in the vicinity of the site caused by sea-level and vegetation changes coincident with the amelioration of temperatures at the end of the Pleistocene are clearly marked in the faunal remains at the site. Largely correlated with the faunal changes (which includes the introduction of marine resources to the cave at about 12,000 B.P.) are changes in the stone artifact assemblages. Three industries are recognized in the sequence: the Robberg, characterized by microbladelets produced from bladelet cores and a few small scrapers and backed tools; the Albany, characterized by large scrapers and an absence of backed tools; and the Wilton, characterized by a variety of Formal Tools including relatively large numbers of small scrapers and backed tools. These changes in artifact-manufacturing traditions are interpreted as signaling adjustments to changing environmental conditions. An explanation for these adjustments is not sought in a simple cause-and-effect relationship between the environment and the cultural response; artifact changes are seen instead as the result of a twofold process, with the environment acting as an external stimulus to change, and the direction of the artifact change governed by the selection of a range of possibilities offered by the technology of the Later Stone Age sensu lato that was widespread in subequatorial Africa during the last 20,000 years.
Abstract: Artifact occurrences from the alluvial fills of the Lower Vaal Basin, South Africa, are summarized with reference to a revised stratigraphic framework for these deposits. The Older Gravels, Younger Gravels, and the Riverton Formation record the history of Cenozoic denudation in this region and demonstrate repeated climatic fluctuations both moister and drier than the semi-arid present. The settlement geography and geology of eight important Acheulian stone-tool collections from the Younger Gravels and lower Riverton Formation are described. These occurrences, known as Homestead, Larsen, Riverview VI, Newman's Pont, Canteen Koppie, Pniel, Power's Site, and Muirton, indicate Acheulian settlement on low terraces next to the main river, in channelways during low flow periods, and on low, rocky slopes adjacent to the floodplains.
Abstract: Geological and biological data for the period 0-40,000 B.P. suggest that variations in precipitation and evaporation along the temperate and tropical margins of Australia and North Africa are closely related to variations in the position and strength of the subtropical anticyclones. Such changes in the subtropical anticyclones seem related to changes in the position and wave amplitude of the subtropical westerly jet stream. A dynamic interpretation of the inferred palaeoclimates suggests that important additional factors were the distribution of surface temperature anomalies over Siberia and the Sahara at 30,000 B.P.; the location of North Pacific and North American surface temperature anomalies at 24,000 B.P.; compression of the westerlies over Tasmania during 20,000-15,000 B.P.; breakdown of the summer monsoon during 17,000-12,000 B.P.; and a possible change in the slope and nature of the Intertropical Convergence during 11,000-7,000 B.P. Major environmental changes associated with the above influences were heavy rainfall, high lake levels, and increased fluvial activity in southern Australia and along both margins of the Sahara between 40,000 and 20,000 B.P.; low lake levels in the Afar at 30,000 B.P.; intertropical aridity and dune-building along the tropical margins of the Sahara and Australia, and desiccation in semi-arid New South Wales during the interval 17,000-12,000 B.P.; and very high lake levels and increased precipitation in the Sahel and in northern and southern Australia from 11,000 B.P. to 5,000 B.P. The past and present role of the desert anticyclones in controlling the start and the close of the arid phases is demonstrated, as is the correlation between Southern Hemisphere pressure systems and Saharan rainfall, and between Northern Hemisphere circulation changes and Australian rainfall. The subtropical anticyclones may act as buffers when the thermal balance between the two hemispheres is upset by an excess of surface ice in any one hemisphere, and this influences the climate well beyond the deserts.
Abstract: It is as important to measure the degree of risk involved as it is to measure the probable return from an investment project. The expected returns from such a project are usually calculated from a unique set of parameters whose values are the [`]best guessed estimates' available at the time of making the projection. Risk analysis involves the selection of the range of possible values for each major variable and an estimation of the probability of each value occurring. In the computations used in this paper the choice of values is made by Monte Carlo simulation. As agricultural problems are involved, care has been taken of the linkage effects between variables and of the dependence of one year's results on the outcome of the previous year. The dynamic nature of the problem and the iterative calculations involved in Monte Carlo techniques favour a computer-based model. The paper is concerned with the application of this approach to rangeland livestock projections.
Abstract: Three algebraic infiltration equations (Kostiakov's, Horton's and Philip's) were examined to determine which one would best fit infiltrometer data collected from a variety of mostly semi-arid rangeland plant communities from both Australia and the United States. Approximately 1,100 infiltrometer plots were included in the analysis. Results indicated that, in every instance, Horton's equation best fit the infiltrometer data. Variability of "point" measures of short-term infiltration rates were never satisfactorily accounted for by using either Kostiakov's or Philip's equation. Though Horton's equation provided a best fit to the overall infiltration data, R2 values indicated a potential usefulness of this equation only under the certain conditions that were sampled in several rangeland plant communities in the Northern Territory, Australia. The equation could not be considered consistently useful under conditions sampled on rangelands in the United States.
Abstract: The hydrologic balance of a semi-arid grassland near Deniliquin, New South Wales, was measured with a precise weighing lysimeter from January through December 1974. Records were analysed for quantity and duration of dew and actual evapotranspiration. Dewfall was negligible during summer (January, February, December) but for the remainder of the year it amounted to 1.2% of class A pan evaporation, 2.5% of precipitation or 3.9% of actual evapotranspiration. Since 90% of the dew fell between May and September, which coincides with the active growing period of grassland, it possibly plays a role in plant growth and species composition. Maximum dewfalls were received during winter months. In June, dew amounted to 6.1% of pan evaporation, 15.6% of actual evapotranspiration or 29.8% of precipitation. Average monthly maximum dew duration of 17.5 h also occurred in this month. During winter, dewfalls of up to 0.56 mm day-1 were recorded, which amounted to 57% of actual evapotranspiration or 27% of pan evaporation. The role of dew in the reduction of evaporative loss of soil water is emphasized. Based on a detailed energy partitioning exercise in May, it was demonstrated that about 80% of net radiation was utilized for evapotranspiration, of this dew used over 22% which would have otherwise been used largely in evapotranspiration of soil water.
Abstract: Paleomagnetic pole positions, ocean-floor magnetic anomalies and least-squares fits of continental edges show that most Phanerozoic orogenic belts have formed at or near the borders of continents and island arcs. Large areas of old ocean floor have vanished, probably along former continental margins and islands arcs. Thus most Phanerozoic orogenic belts must include subduction zone effects. Superposed on them may be effects caused by self-heating of thick [`]geosynclinal' piles of continental margin sediment. It is not yet clear how to discriminate self-heating from slip-zone heating effects. Paleomagnetic data also show that rigid areas of the continental crust have been in relative motion for at least 2500 m.y. These data imply that plates existed and that subduction may have been active since at least the beginning of Proterozoic time. Paleomagnetic data and mapping suggest that some Proterozoic African orogenic belts may not have originated by plate-tectonic processes, though the evidence is inconclusive. There is no geophysical evidence for or against the existence of Archean plates. The causes of Archean orogenesis are speculative. Some plate-tectonic models appear to differ significantly from the actual orogenic belts they purport to describe. In particular, long-continued subduction does not necessarily give rise to continental accretion, but in some cases may actually involve tectonic erosion of the overriding plate by the slip zone. Subduction of continental crust is likely to have taken place in the Alps and probably in many other orogenic belts. Probable continental margin sequences of pre-Mesozoic age are common. Some of these could have been deposited along Atlantic-type continental margins, but in no case has the matching continental fragment been identified. Without such identification, Atlantic-type continental margin sequences cannot be readily distinguished from sequences formed at the borders of new ocean basins next to wide, migrating, active island arcs ([`]marginal basins'). Additional evidence suggests that the Cambro-Ordovician sequences of northwest Scotland cannot be deposits formed on an Atlantic-type continental margin, and that the same sequence in northwest Newfoundland may not have formed along such a margin. The plate tectonic significance of most orogenic features is unknown or controversial. How andesites originate is not understood; the reasons for the systematic potash variations with depth to the slip zone in andesite suites are unknown; and the significance of foreland deformation, of slaty cleavage and of regional metamorphism are disputed. Nevertheless, the solutions to all of the above problems are considered attainable, but will require a constant interplay between field, laboratory and theoretical work.
Abstract: The study of ungulate populations in south Asia has lagged behind comparable efforts in Africa. The need for intensive study of Asian wildlife communities is critical. The existing data concerning the numbers and habitat needs of selected mammalian herbivores in south Asia are reviewed. It is concluded that special attention must be given to those species of ungulates which appear to exploit early to mid-succession vegetation stages. These species are especially vulnerable to decline in small parks and reserves where vegetational succession can move rapidly to a climax condition. The ungulate fauna of south Asia is unique and generalisations based on studies in Africa are not necessarily applicable to the subcontinent. The Cervidae emerge as an important radiation in Asia with extensive adaptation to browsing niches.
Abstract: In this paper an attempt is made at problem identification and resultant policy implications of the Sahel-Sudan region of West Africa. This region suffered a prolonged drought during 1968-1973 including famine and losses of property. The approach of the study is predicted upon the needs for an interdisciplinary, comprehensive and integrated evaluation to assist policy planning and avoid costly mistakes resulting from oversights and narrow examinations that result from a single sector or project approach. Thus, the distinguishing characteristics of the region are identified in section one of this paper including political and geographic, economic, climatic, international and resource base of the region. In Section 2, the major problems of the region are explicated in three process models referred to as the vicious circles. These include the ecological-agricultural circle, the human opportunity circle and the traditional-modern circle. It is shown that the regions fragile ecology has succesively deteriorated, the human opportunities have been restricted for the majority of the people in the rural areas and the modern sector has been subsidized by heavily taxing the traditional sector. In Section 3, it is contended that breaking of these vicious circles provide the necessary and sufficient condition for the region's long term viability. And a number of policy parameters are expounded upon. The main theme of this paper is diagnostic and its implications are worldwide, both in terms of methodology and contents.
Abstract: Samples of Hemiptera were taken in September 1972, from areas of carboniferous limestone grassland which were burnt in April and May 1972, and from adjacent unburnt areas. Significantly larger numbers of species, of both Heteroptera and Auchenorhyncha, were recorded from the unburnt areas, and the species-diversity of the samples was significantly greater. The effects of burning on individual species are considered in relation to their biology and the effects of other kinds of management. The results are discussed in relation to the management of grassland for the conservation of wildlife, and a short review of the effects of burning on populations of invertebrate animals is made.
Abstract: Summary This paper presents a description of the temporal and spatial distribution of rainfall within the Serengeti Ecosystem, Tanzania. Ecosystem and Regional patterns are discussed with respect to synoptic processes, vegetation zonation, phases of primary production and the distribution and migrations of large mammals.
Abstract: The Loma Mountains (2090 m), situated in lowland south Guinea savanna in Sierra Leone, are shown to have a cooler and more mesic climate than the savanna region. A temperature lapse rate of 7.5o C/1000 m is calculated using means for the dry, dry/wet, wet and wet/dry seasons of the year. In the montane grassland the life forms of the species are predominantly hemicryptophytic, and the biological spectrum is closer to that of temperate grasslands than to the savanna type, although the adverse conditions are still dry-season drought and fires. The phytogeographical distribution of the flora indicates a 44% widespread, truly montane to montane/savanna element and a 43% West African endemic element. In the Guinean highlands, the Loma/Tingi group shows about 10% disjunction of its grassland flora with other African mountains outside West Africa.
Abstract: Although soil and forest conservation measures in Africa were reflected in the early legislation of some countries, it was first with the nature reserve and national park concept of the late 1890s and early 1900s that entire habitats with their vegetation and animals became protected. Yet little attention was paid to interactions between various components of the ecosystem, particularly between plants and animals. In the 1940s Belgian and French ecologists published three pioneering works on the function of African ecosystems, but they were apparently not very much read in English-speaking countries. However, in the 1950s field investigations in the Congo (Zaire) and Eastern Africa by American and European workers threw more light upon the important role played by larger wild mammals in the ecology and economy of African grasslands. At the same time the pressure on these mammals and their habitats was increasing rapidly owing to human population growth and land hunger. Simultaneously the African countries emerged as politically independent states. It became clear to IUCN that urgent conservation measures, based on ecological facts, must be undertaken in cooperation with the new African states. This led to the so-called African Special Project, of which one phase was the 1961 Arusha Conference on [‘]Conservation of Nature and Natural Resources in Modern African States 039;. This conference became a turning point in the conservation history of Africa, and the 1960s saw a remarkable progress in conservation that culminated in the 1968 African Convention on Conservation of Nature and Natural Resources, signed by the African Heads of State in 1969. However, without being fully implemented the African Convention cannot create miracles. The conservation situation in Africa is continuously aggravated due to the using up of the renewable natural resources 039; capital. This is in turn caused by the increase of human and livestock populations, which in most countries no longer correspond to the carrying capacity of the environment.
Abstract: Agricultural development is a complex undertaking because of the numerous factors involved, including those of a physical and non-physical nature. Land and water have often been (and are nowadays sometimes still) regarded as a means to grow crops. This approach, based on the utility principle, may lead to dismal failures. Fertile lands were thus turned into a saline wilderness within a relatively short period. In the above approach the management problem, i.e. the problem of cause-and-effect relations has been neglected. More than is the case at present, proper planning must relate the physical, environmental, economical, and social factors involved. But the integration of all these factors encounters some major difficulties of which insufficient data and lack of an exact and comprehensive methodology are the most serious. But planning cannot be postponed indefinitely or until the last information has been obtained. Effective development of agriculture, of which water resources management forms an important part, is undoubtedly one of the greatest needs of to-day's world. The complexity of the problem has outgrown traditional problem-solving methods. The principal aim of this article is to describe in brief some recent developments in water resources management methods and water supply optimization techniques. Two models are discussed: a linear programming model for finding optimum solutions of water supply and a mathematical groundwater basin model, which is capable of simulating various extraction and replenishment flows and predicting the consequences of future engineering works. The unique feature of these two models is that the output of the linear programming model can be used direcly on the groundwater basin model to test the physical validity of the economic solution.
Abstract: Igbozurike, M.U., 1974. Vegetation burning and forest reservation in a segment of the forest--savanna mosaic of Nigeria: a preliminary investigation. Landscape Plann., 1: 81-103. As a man-induced process and a problem said to require solution, vegetation burning has reached epidemic proportions in large segments of Nigeria's forest--savanna ecotone. The dimensions and implications of this phenomenon, the necessity for its control, and the control mechanics especially by way of forest reservation, and the attendant biogeographic changes are the subject of this investigation. On the one hand, the constitution into a forest reserve of a grassland area that used to be regularly burned makes for greater biotistic wealth, and this furnishes a basis for a greater degree of game harvesting. On the other hand, and more important, for various ecological, economic, physical, and cultural reasons and as alternative means for satisfying the needs met by fire are non-accessible or unavailable, the exclusion of fire from most of the area studied is certain to do more harm than good.
Abstract: The microfungi of an alkaline soil from an open-savannah in the Pretoria district of the Transvaal were surveyed using the dilution plate technique, the soil plate technique and a soil washing method. Over 14 months 127 species representing 53 genera were isolated. The most prevalent species found were Penicillium spp.; Fusarium spp.; Trickoderma viride; Gliocladium roseum; Aspergillus spp. ; Mucor spinosus; Spicaria violaceae and Chaetomium globosum. The results are discussed with particular reference to comparable surveys carried out in the Western Transvaal.
Abstract: A model for estimating soil water content on native rangeland was tested at Sidney, Montana. Based on the Penman combination method for estimating potential ET, the model includes factors to account for crop development, limiting soil water content, and increased evaporation after rain. The model gave reasonable estimates of actual soil water conditions within a 15% limit suggested as being practical for rangeland management purposes.
Abstract: The environment of the highveld of south-central Africa is such that most grasslands are only temporary and the spread of trees into grassland--[`]bush encroachment'--is only checked by periodic burning. Fire, the commonest tool for bush control, is inefficient, manual control is excessively demanding of labour, mechanical control methods are too costly, and chemical treatment has not yet proved to be satisfactory. Only biological control, using goats, appears promising but nevertheless is unpopular. It is suggested that game-ranching, using the natural mixed herds of grazers and browsers, would be a more ecologically-appropriate means of producing edible protein than burning and grazing. The proposition merits detailed re-examination.
Abstract: Daily total rainfall depths served as input to a computer program that estimated infiltration and subsequent evaporation. Printed output stated when a predefined start of the growing season occurred at Tombstone, Ariz., using official precipitation records from 1897 to 1970. The output listed moisture sequences by assigning a wet or dry status to the soil. The start of the growing season for perennial range grasses, defined as the presence of four consecutive days of wet soil, has occurred from June 8 to as late as early September, with a median start at July 14. The total number of wet days averaged 38 during the 4-month period of June to September. Every year had at least one period of drought within the growing season; drought periods occurred an average of 6 times and could exceed 12. The average maximum dry period was 18 days; the corresponding wet period was 21 days. The starting wet period averaged 13 days and the ensuing dry period was 5 days. The maximum wet period tended to occur earlier in the season than the dry.
Abstract: A system of classification of the biotic communities of the world, taking into account vegetation, flora, and fauna, is needed for purposes of global conservation of species and ecosystems. In this paper the world biota are classified, tentatively, into provinces. These are based initially on biomes, subdivided primarily on the basis of major faunal regions, and regionally on the basis of important faunistic and floristic differences. The usefulness of the system is considered in relation to the distribution of national parks and equivalent reserves throughout the world. The system presented here is preliminary and subject to modification and revision on the recommendation of biogeographers and ecologists concerned.
Abstract: This paper discusses the basic relationship between the dietetic needs of pastoral people, the number of stock they must keep to supply these needs, and the productive capacity of the environment. While overgrazing and erosion in pastoral areas is usually attributed to [`]prestige' overstocking, it is shown here that there is a basic minimum number of animals required to support a human family. This requirement is usually about 3 Standard Stock Units each of 500 kg live-weight per head, but varies from 2·5-4·5 according to the ecological conditions, and is made up of various classes of stock that are kept for meat or milk. Where rising human population becomes too great to permit each family to maintain this necessary minimum herd, damage to the environment through overstocking becomes inevitable. In addition, by competing for the available milk supply, the pastoral peoples inevitably starve the calves and depress the quality of their stock, especially where human populations are high. The prevalent [`]overgrazing' situation is seen as one of human over-population in many areas--requiring the removal of humans, or alteration of their dietetic habits, as well as mere reduction of stock numbers. Possible methods of alleviating the situation include partial dependence on bought grain, or settlement on irrigation schemes, but none are easy or short-term.
Abstract: Of all the continents, Africa has the highest proportion of land fit for agriculture. The principal vegetative cover on this land is grass, which, when it is well managed, gives good protection against erosion. Unfortunately, much of this grassland, and especially that north of the Sahara desert, is so heavily overstocked that it produces far too little forage for livestock, and scarcely any cover remains for protection of the soil. The very low productivity of the livestock is a major factor in the poor nutrition of the people--especially of young children suffering from kwashiorkor. It is still a common practice to keep as many cattle as possible, as an indication of the owner's social status and wealth. Consequently in Africa the commonest problems include a shortage of forage and inefficient use of what is available. This condition needs to be alleviated by increasing the output from native grassland and producing more forage on arable land. Each country needs a competent organization to cope with these problems. Improved practices such as rotational grazing and culling unproductive animals may increase the yield of the livestock from two to ten times. All such practices can be gradually adopted by the pastoral people, and by those doing mixed farming, with the help of their own technically trained youth. By the use of these practices, along with family planning to hold the population near the present level, it will be possible for the people to have an adequate diet and for the soil and other natural resources to be maintained.
Notes: UK2.00 xD;edited by D. J. Pratt and M. D. Gwynne ; from contributions by J. R. Blackie ... [et al.]. xD;ill. ; 25 cm. xD;Includes index. xD;Bibliography: p. 289-303.
Notes: Edited by D. J. Pratt 38; M. D. Gwynne. Hodder 38; Stoughton, London Sydney AucklandToronto : ix + 310 pp., 35 figs, 4 maps in colour, 14 pis, and 33 tables, 25.5 215; 19 215; 3 cm, 163;7.50 (paperback available only in ELBS areas, 163;2.00), 1977
issn = "0376-8929
