Browsing Okavango Research Institute (ORI) by Title
-
Swatuk, L.A.; Motsholapheko, M. (Elsevier, www.elsevier.com/locate/pce, NaN, 2008)[more][less]
Abstract: The Boteti River is an ephemeral outflow of the Okavango River. It lies in the north-western part of Botswana where about 25,000 people reside across a number of widely scattered villages and informal settlements. The river, with its seasonal streams and pans, is vital to the livelihoods of these people, their livestock, and the wildlife that share this physical space. A combination of factors has led to widespread degradation of the physical resource base – both in the river bed itself and in the wider environment. As part of its outreach role, the Harry Oppeheimer Okavango Research Centre has undertaken a multi-year project along the Boteti River to assist people there with the rehabilitation of their resource base. The globally influential concept of integrated water resources management (IWRM) provides the analytical framework, in particular its emphasis on dialogue and stakeholder participation. The project has three primary aspects: facilitation of a dialogue platform; action-research; outreach and information dissemination. After two years of implementation, the project has collected a good deal of data and established a River Basin Forum with a common vision. However, the project continues to face difficulties in implementation: participation is limited; myths regarding resource degradation are difficult to dispel; meaningful communication among differently empowered actors is hard to achieve; and there are numerous human, financial and technological limitations. The primary researchers continue to alter their methods in the hope of achieving a functioning River Basin Committee (RBC), but observe that the globalized ideals of IWRM are, in this particular case at least, of limited use when attempting to alter localized management practices in basins with deeply embedded social and cultural practices. URI: http://hdl.handle.net/10311/504 Files in this item: 1
Motsholapheko2008IntegratedWater.pdf (1.154Mb) -
Toteng, E.N.; Mbaiwa, J.E.; Moswete, N.N. (Botswana Society, NaN, 2005)[more][less]
Abstract: This paper is derived from a broader study that examined community attitudes and perceptions towards ecological issues in Maun and Gaborone to determine how these could be harnessed towards ecologically sustainable urban development. The major problem in the two study sites is that there has been rapid urban growth since the 1970s, but very little attention has been devoted to the environmental implications of that growth. The environmental issues on which community attitudes and perceptions were sought included the following: urban water and waste water; urban solid waste management; urban impacts on wildlife; and urban energy conservation and management. These issues were selected on the basis of what the authors were able to obtain socio-ecological data on, given the time and financial constraints of thestudy. The urban ecosystems management model is used as an analytical framework that could be further harnessed by policy and decision-makers to mobilize stakekeholders towards sustainable urban development. A social survey method was used to generate data among heads of households in Maun and Gaborone. It was found that most ordinary members of the community were not involved by government authorities in decision-making affecting natural resource use and environmental issues. However and in general, the communities had positive attitudes and perceptions towards environmental issues. The major draw-back is that these communities are generally not consulted by state agencies in decision-making processes affecting their environment. It is concluded that this is inimical to ecological urban development. URI: http://hdl.handle.net/10311/945 Files in this item: 1
Toteng 2005 Community.pdf (2.443Mb) -
Kgathi, D.L.; Ngwenya, B.N. (Botswana Society, http://www.botsoc.org.bw, NaN, 2005)[more][less]
Abstract: This paper examines the impact of Community-Based Natural Resource Management (CBNRM) in Ngamiland over the past ten years. It shows that CBNRM has made some strides in strengthening and creating new organisations/ institutions, empowering local communities, creating social networks and improving the institutional capacity of community trusts. Communities receive benefits from employment opportunities, social infrastructure, provision of transport, and assistance on meeting the costs of funerals. However, the contribution of most of the benefits to livelihood diversification is limited as they mainly accrue to the communities rather than individuals. The programme faces many challenges, such as limited institutional capacity for running organizations, insecurity of tenure, stakeholder conflicts, mismanagement of funds, and problems of how to use and equitably distribute the financial benefits to individual households. URI: http://hdl.handle.net/10311/965 Files in this item: 1
Kgathi2005 CBNRM.pdf (2.852Mb) -
Sebele, L.S. (Elsevier, www.elsevier.com/locate/tourman, NaN, 2010)[more][less]
Abstract: The impact of Community-Based Natural Resource Management (CBNRM) is seen by many as a ‘win-win’ situation with reference to natural resources conservation and the improvement of local communities’ livelihoods. However, community engagements in CBNRM and tourism have elicited many views as far as natural resources utilization is concerned. Some affirm the importance of CBNRM; others question it, while others call for its improvement. The premise of this study is to investigate the benefits and challenges of community-based tourism in one community of Botswana. Results show that although some benefits have been identified, there remain many challenges for the Khama Rhino Sanctuary Trust (KRST). It is evident that for community-based tourism to bring more benefits for locals, more interaction is needed between them and the Trust management. Increased local involvement and participation will help to ensure that people are empowered and the conservation of natural resources takes place. This paper asserts that community-based ventures, if properly run and managed, can promote the conservation of natural resources and increase local benefits through participation in tourism activities. Description: Case Study URI: http://hdl.handle.net/10311/503 Files in this item: 1
Sebele2010TourismVentures.pdf (1.383Mb) -
Mmopelwa, G.; Ngwenya, B.N. (Academic Journals, December 4, 2010)[more][less]
Abstract: The Okavango Delta is the largest multi-species and multi-gear fishery in Botswana. However, there is lack of an understanding of the nature of fish market in the Delta. The objectives of the survey were (1) to identify and describe the socio economic profile of the fishers in the fishing market, (2) to describe the operations of the market and (3) to identify market constraints of fishing. A structured questionnaire was used to collect data from fishers in four study sites in the Delta. The study revealed that fishing market in the Okavango Delta is very ‘informal’ in nature, with almost no intermediaries, and catering only for the local population. Lack of preservation facilities, transport, low levels of skills and lack of access to credit are the various constraints facing fishers. URI: http://hdl.handle.net/10311/739 Files in this item: 1
-
Huntsman-Mapila, P.; Kampunzu, A.B.; Vink, B.; Ringrose, S. (Elsevier; http://www.elsevier.com/wps/find/journaldescription.cws_home/503361/description#description, NaN, 2005)[more][less]
Abstract: [Please note that chemical formulae do not display properly]:The siliciclastic sediments of the Okavango inland Delta of northwest Botswana have a modal composition of quartz arenites and result from a complex history, including transport by river and deposition in a nascent rift basin located in a desert environment with input of aeolian sands. The geochemical composition of sediments from the Okavango Delta was determined in order to constrain the role of weathering at the source and the composition of the source rocks. The chemical analyses and the interelement ratios show a broad compositional range usually encompassing the PAAS composition. The chemical index of alteration (CIA) values and the A-CN-K diagram define an evolution trend which can be interpreted using a mixing model involving a strongly weathered component which corresponds to the sedimentary fraction transported by the Okavango River and a relatively immature component which corresponds to the aeolian sand component of the Okavango sediments. Field geological data supported by geochemical ratios involving elements with affinity for mafic-ultramafic and felsic rocks such as Th/Cr, Th/Sc, La/Sc, La/Co and Eu/Eu* support a source area including mafic-ultramafic and felsic rocks, with or without intermediate rocks. The relationships between certain elements (Cr-Ni, Na2O-Al2O3, K2O- Al2O3) refine the interpretation by pointing to the existence of at least three source rock end-members, including a felsic rock source and pyroxene-rich and olivine-rich mafic-ultramafic source rocks. Proterozoic granitoid-gabbro and related volcanic and ortho-metamorphic rock complexes exposed in NW Botswana and adjacent Angola and Namibia are the source rocks of the sediment component which was mixed with aeolian sand and interacted with a variable proportion of diagenetic carbonates to produce the Okavango sediments. Description: This paper was a contribution to the SAFARI 2000 Research Project. URI: http://hdl.handle.net/10311/153 Files in this item: 2
huntsman_mapila_sedgeo.pdf (6.089Mb)license.txt (1.998Kb) -
Daka, P.S.; Obuseng, V.C.; Torto, N.; Huntsman-Mapila, P. (South African Water Research Commission http://www.wrc.org.za, NaN, 2006)[more][less]
Abstract: Deltamethrin concentrations were determined in 35 sediment samples collected from three different habitats: channel, lagoon and pool sites from Xakanaxa in the Okavango Delta, NW Botswana. The samples were Soxhlet-extracted in acetone to extract deltamethrin residues and subsequently cleaned-up with silica gel 60. The final determination was carried out with a gas chromatograph equipped with an electron capture detector (GC-ECD). The sample work-up and determination gave deltamethrin recoveries of 54 to 97%, and detection limits of 0.004 mg/kg dw. The concentration of deltamethrin residues in the sediment samples collected from the three sprayed areas in the Okavango delta ranged between 0.013 and 0.291 mg/kg dw, with the highest concentrations observed in samples obtained from the pool sites. Analysis of samples for organic matter content showed percentage total organic carbon (% TOC) ranging between 0.19% and 8.21%, with samples collected from the pool having the highest total organic carbon. The concentrations of deltamethrin residues and the % TOC in sediment samples showed a similar trend with the highest levels recorded in the pool samples. These data confirmed that a simple method based on GC-ECD, after Soxhlet extraction, was robust enough to enable quantification of deltamethrin in the sediments, because comparable results were obtained with a more sophisticated system consisting of a GC coupled to a mass spectrometer with a time of flight (TOF) analyser. URI: http://hdl.handle.net/10311/650 Files in this item: 1
Daka_WSA_2006.pdf (1.231Mb) -
Magole, L.I.; Gojamang, O. (Botswana Society, NaN, 2005)[more][less]
Abstract: Despite the existence of a model of the life cycle of tourist destinations (Butler, 1980, adapted by Prossor, 1994), non-beach tourist destinations are seldom subjected to an appraisal of their evolution and an assessment of the developmental stage or phase the particular destination may be in. In this paper we explore the dynamics of tourist visitation to national parks and game reserves in Botswana over a period of ten years (1995-2004. We have used data on tourists collected by the Department of Wildlife and National Parks (DWNP) staff at national park and game reserve gates, which they summarize on a monthly basis and forward to the Parks and Reserves Reservation Office (PARRO). We conclude that the development of tourism in the Chobe National Park and Moremi Game Reserve follow Butler’s model and show signs of stagnation. Based on the findings of the paper, a recommendation to review the Botswana Tourism Master Plan (2000) is suggested in order to align it with realistic tourism trends of the national parks and game reserves. URI: http://hdl.handle.net/10311/939 Files in this item: 1
Magole 2005 Dynamics.pdf (2.198Mb) -
VanderPost, C. (Botswana Society, http://www.botsoc.org.bw, NaN, 2005)[more][less]
Abstract: During the years 1849 to 1900 the first maps of (portions of) the Okavango Delta region in Ngamiland were produced by missionaries, explorers, travellers and adventurers. Considerable progress was made from the first attempt by Livingstone and Oswell in 1849 to the work by Passarge at the turn of the 20th century. There were great improvements in the positional accuracy of Lake Ngami, the initial attraction of the region, and many of the river courses and other features in the Okavango-Ngamiland region, as maps became much more detailed. This paper describes the progress from the first rather inaccurate mapping attempts to the more sophisticated work produced just before the turn of the 20th century when the word ‘Okavango’ actually began to appear on maps. These early mapping efforts laid the foundation for the cartography of the colonial era. URI: http://hdl.handle.net/10311/955 Files in this item: 1
VanderPost 2005 Early maps.pdf (2.241Mb) -
Thakadu, O.T.; Mangadi, K.T.; Bernard, F.E.; Mbaiwa, J.E. (Botswana Society, NaN, 2005)[more][less]
Abstract: This study aimed at assessing the economic contribution of safari hunting to rural livelihoods in the Okavango Delta in Botswana, using Sankuyo village as a case study. This study was carried out between June and July 2004. It employed primary and secondary data sources. Findings indicate that, within the context of Community Based Natural Resources Management (CBNRM), safari hunting has socio-economic benefits accruing to Sankuyo (at household and community level). These benefits include income(coming in the form of cash dividends and through employment) that have been generated, and the development of recreational and household sanitation facilities that has taken place in the village. The study also found that the distribution of safari hunting benefits among Sankuyo households is fairly equitable. Income from safari hunting has also been used to purchase communally owned resources such as vehicles. Because of these benefits, the people of Sankuyo have since developed positive attitudes towards safari hunting. These findings thus suggest that safari hunting is important in improving rural livelihoods in the Okavango Delta while at the same time promoting natural resource conservation. URI: http://hdl.handle.net/10311/944 Files in this item: 1
Thakadu 2005 Economic.pdf (2.744Mb) -
Mladenov, N.; McKnight, D.M.; Wolski, P.; Ramberg, L. (The Society of Wetland Scientists, NaN, 2005)[more][less]
Abstract: In the Okavango Delta in Botswana, dissolved organic matter (DOM) transport is controlled by the slow movement of an annual flood ‘pulse’ across permanently and seasonally flooded wetlands, known respectively as the Permanent Swamp and Seasonal Swamp. We studied temporal and spatial variations in fluorescence index (FI) and specific UV absorbance (SUVA) of DOM to identify DOM sources and fate during the flood. Dissolved organic carbon (DOC) concentrations ranged from 2 to 25 mg C L21 in channels of the Delta, with seasonal floodplains having consistently higher concentrations. Chemical indices, such as DOC concentrations, conductivity, specific UV absorbance (SUVA), fluorescence, total dissolved nitrogen, and chlorophyll a, were analyzed for channel and floodplain sites in the Seasonal Swamp. DOC concentrations increased during the rising limb of the flood in the Seasonal Swamp. SUVA of whole water samples and fluorescence index (FI) of fulvic acids isolated from channel and floodplain sites changed in a manner indicating the release of DOM by leaching of plant litter during the flood. After the flood receded, DOC concentrations and fulvic acid content decreased, and microbially-derived sources of organic matter dominated. Along two river reaches, measuring over 400 km each, variations in DOC concentrations were primarily due to geomorphology, with the effects of the annual flood overprinted atop the spatial controls. Increasing downstream DOC concentrations were found to be a product of inundation of DOC-rich seasonal floodplains and evaporation-enriched waters downstream. Increasing SUVA, dissolved nitrogen, and fulvic acid content, and decreasing FI downstream suggested microbial processing of terrestrial DOM and possible release of nutrients incorporated in the DOM. URI: http://hdl.handle.net/10311/526 Files in this item: 1
Mladenov2005FLOODynamics.pdf (2.529Mb) -
Brooks, C.; Bonyongo, C.; Harris, S. (Wildlife Society http://joomla.wildlife.org/index.php?option=com_content&task=view&id=43, NaN, 2008)[more][less]
Abstract: Global Positioning System (GPS) collars are increasingly being used to study fine-scale patterns of animal behavior. Previous studies on GPS collars have tried to determine the causes of location error without attempting to investigate whether the accuracy of fixes provides a correspondingly accurate measure of the animal's natural behavior. When comparing 2 types of GPS collar, we found a significant effect of collar weight and fit on the rate of travel of plains zebra (Equus burchelli antiquorum) females in the Makgadikgadi, Botswana. Although both types of collar were well within accepted norms of collar weight, the slightly heavier collars (0.6% of total body mass [TBM]) reduced rate of travel by >50% when foraging compared with the collar that was 0.4% of TBM. Collar effect was activity specific, particularly interfering with grazing behavior; the effect was less noticeable when zebras crossed larger interpatch distances. We highlight that small differences in collar weight or fit can affect specific behaviors, limiting the extrapolation of fine-scaled GPS data. This has important implications for wildlife biologists, who hitherto have assumed that collars within accepted weight limits have little or no effect on animal movement parameters. URI: http://hdl.handle.net/10311/628 Files in this item: 1
Brooks_JWM_2008.pdf (1.039Mb) -
Siele, M.P.; Mubyana-John, T.; Bonyongo, M.C. (Global Science Books http://www.globalsciencebooks.com/index.php?page=shop.product_details&category_id=1&flypage=shop.flypage&product_id=5&option=com_virtuemart&Itemid=56&vmcchk=1&Itemid=56, NaN, 2008)[more][less]
Abstract: Soil cover influences soil biological and chemical processes in various ways. The effects of soil cover (bare soil without litter, litter cover, Mopane tree canopy and grass cover) on soil respiration and microbial population at four sites in the Mopane woodland of north western Botswana were investigated. Soil respiration rates were measured using an infrared gas analyzer. Nitrifying bacterial populations were quantified by MPN on ammonium and nitrite calcium carbonate media, oligotrophs on 1% nutrient agar, actinomycetes on starch casein agar, bacteriovorous protozoans by MPN on sodium chloride agar baited with Enterobacter, and fungal biomass carbon using buried slides were also determined. Soil respiration in different habitats was significantly influenced by type of cover, diurnal temperature variations and soil moisture. Soils under cover showed significantly higher soil respiration than the bare soils. Autochthonous bacterial populations in the Mopane woodland soils consisted mostly of oligotrophs which varied insignificantly between seasons. Fungi were the most dominant microorganisms in all the Mopane woodland soils, with biomass of 162.05 to 282.14 μg C/g soil in the wet season and 11.84 to 44.16 μg C/g soil in the dry season. Microscopic observation of buried slides revealed that fungi play a vital role in holding soil particles together in these soils. The results showed a strong positive relationship between changes in fungal biomass and fluctuation of soil respiration. However, no clear correlation was observed between the variation of soil respiration and other microbial populations (oligotrophic bacteria, actinomycetes, and nitrifying bacteria). Overall these results indicate that in soils under Mopane tree canopy, fungi contribute significantly to soil structure and soil respiration. Other microbial populations consist mostly of oligotrophs which show minimal seasonal variations. Soil moisture significantly influences seasonal fluctuation in soil respiration. URI: http://hdl.handle.net/10311/292 Files in this item: 1
The Effects of Soil Cover.pdf (6.625Mb) -
Mbaiwa, J.E.; Stronza, A.M. (Routledge (Taylor & Francis) www.routledge.com, January 19, 2010)[more][less]
Abstract: The Community-Based Natural Resource Management (CBNRM) program in Botswana aims to achieve biodiversity conservation and rural development in rich biodiversity areas like the Okavango Delta. CBNRM assumes that if rural communities derive benefits from natural resources, they will be obliged to use such resources sustainably. Using the sustainable livelihoods framework, this study analyzes the effects of tourism development through CBNRM on rural livelihoods at Khwai, Sankoyo and Mababe in the Okavango Delta, Botswana, using primary and secondary data sources. Results of long-term surveys and in-depth interviews indicate that the three communities have forgone traditional livelihood activities such as hunting and gathering, livestock and crop farming to participate in tourism through CBNRM. Livelihoods in these villages have been improved as a result. Basic needs such as shelter, employment and income and social services like water supply systems, transportation, scholarships and payment of funeral expenses are now provided to community members and funded with income from CBNRM. Social capital has been built up in order to agree, manage and develop the CBNRM process. These results show that tourism development in these villages is achieving its goal of improved livelihoods, contradicting claims that community development projects are failing to achieve rural development. URI: http://hdl.handle.net/10311/960 Files in this item: 1
-
Mbaiwa, J.E.; Mbaiwa, O.I. (International Journal of Wilderness; http://ijw.wilderness.net/, December NaN, 2006)[more][less]
Abstract: This article examines the effects of veterinary fences on wildlife populations in the Okavango Delta, Botswana. Using data from secondary data sources, findings indicate that the existence of veterinary fences in the Okavango Delta contributes to the decline of wildlife species in Botswana. Veterinary fences are erected to control the spread of livestock diseases in order to protect the European Union beef market where Botswanaâ s beef is largely exported. Migratory wildlife species such as wildebeests, zebras, giraffes, buffalo, and tsessebes have their migratory routes blocked by veterinary fences and hence die from dehydration and entanglements in the fence. Those that get trapped by the fence often become easy kill targets for poachers. Some of the animals have been observed walking along the fence trying to cross. The erection of veterinary fences indicates that the expansion of livestock production into wildlife areas threaten the survival of wildlife in Botswana. To address the problem, an integration of wildlife production with other sectors such as agricultural development should be made a priority at national and local policy levels. This means that the principles of sustainability should be given priority in the erection of veterinary fences in wildlife areas. URI: http://hdl.handle.net/10311/28 Files in this item: 2
license.txt (1.998Kb)mbaiwa_int_j_wilderness_2006.pdf (338.1Kb) -
Mmopelwa, G.; Mosepele, K.; Mosepele, B.; Moleele, N.; Ngwenya, B. (Blackwell Publishing, http://www.blackwellpublishing.com, NaN, 2009)[more][less]
Abstract: The hydrological regime of the Okavango River Basin is the main driver of ecological change in the delta. The delta supports a small-scale fishery which is a source of livelihood for communities within its fringes. The fish resource is particularly important to subsistence fishers, who have limited access to socio-economic opportunities. However, fish availability is subject to ‘concentration and dilution’ effects because of the hydrological regime. As a copying strategy, fishers use a variety of fishing methods to effectively harvest the delta’s fish community across all its trophic levels. This exploitation regime helps to maintain the delta’s species diversity and only reduces fish biomass proportionally across the different trophical levels. Furthermore, fishers have developed different fish-processing techniques to preserve their harvest for low fishing season periods to cope with low food availability. The aim of this paper therefore, was to explore spatio-temporal variations in fish availability and to show how the delta’s subsistence fishers cope with this dynamicity. URI: http://hdl.handle.net/10311/862 Files in this item: 1
-
Heinl, M.; Frost, P.; Vanderpost, C.; Sliva, J. (Elsevier; http://www.elsevier.com/wps/find/journaldescription.cws_home/622855/description#description, May 8, 2006)[more][less]
Abstract: Satellite imagery derived fire history data for the southern Okavango Delta, Botswana from 1989 to 2003 were used to analyse the temporal and spatial distribution of fires and to assess changes in fire activity. Maximum fire activity was encountered for 1997 with 24.1% of the study area burned. The annual extent of the burned area fluctuated considerably, but there appeared to be a regular oscillation apparently induced by floodplain fires. The main fire activity on drylands is in September at the end of the dry season, while most floodplains burn earlier in the year. Both burning of floodplains and drylands appear to peak prior to floods and rainfall-events, respectively. Areas with highest fire frequency were outlined and spatial analyses showed that fires on the drylands are largely due to burning of adjacent floodplains. The floodplains were therefore identified as the centres of fire activity, being the regions with the highest fire frequency and serving as source of fires spreading into drylands. Floodplains showed higher fire frequencies compared to drylands, but no increase in fire activity was detected over the study period for both floodplains and drylands. Description: The study was part of the project 'Fire regime and vegetation response in the Okavango Delta, Botswana' funded by the Volkswagen Foundation, Germany and carried out by the Chair of Vegetation Ecology, Technische Universitaet Muenchen, Germany in collaboration with the Harry Oppenheimer Okavango Research Center (HOORC, University of Botswana) and University of Pretoria, South Africa. Financial support was also given by Conservation International Botswana and the German Academic Exchange Service (DAAD). URI: http://hdl.handle.net/10311/151 Files in this item: 2
heinl_j_arid_env.pdf (392.9Kb)license.txt (1.998Kb) -
Mubyana-John, T.; Wutor, V.C.; Yeboah, S.O.; Ringrose, S. (Academic Journals. http://www.academicjournals.org/SRE, NaN, 2007)[more][less]
Abstract: The influence of wild fires on microbial community structure, soil organic matter, sulphur oxidising and nitrifying microbial populations in the floodplains of the Okavango Delta of Botswana was assessed. Microbial community structure was assessed by phospholipids ester-linked fatty acids (PLFA) quantification while microbial sulphur oxidisers were assessed by Most Probable Number (MPN). Community structure assessment showed that burning shifted the microbial community structure from single cellular bacteria being the dominant groups to filamentous fungi and actinomycetes being the most dominant groups. Generally burning increased the fungal component (18:2 w6) matrix from 3.40 to 8.35 while the actinomycetes and sulphur reducing bacterial (10 Me 16:0) component also increased from 1.02 to 1.70 mostly in the floodplains. Generally, the organic matter content declined with burning. However, the influence of burning on soil pH was non conclusive. Soil microbial biomass carbon increased slightly after the fire. The number of heterotrophic and nitrite-oxidizing and sulphur reducing bacteria increased. Overall, these results indicate that burning significantly alters the microbial community structure as large above ground losses of nutrients during and after burning often results in low quantities of nutrients released into the soil. URI: http://hdl.handle.net/10311/349 Files in this item: 1
Fire and.pdf (2.461Mb) -
Omari, K.; Mubyana, T.; Matsheka, M.I.; Bonyongo, M.C.; Veenendaal, E. (South African Journal of Botany http://www.elsevier.com/wps/find/journaldescription.cws_home/707238/description#description, NaN, 2004)[more][less]
Abstract: Effects of flooding on soil nitrogen (N), and asymbiotic nitrogen fixing bacterial (diazotroph) populations of the Okavango Delta were investigated. Diazotrophs from the rhizosphere of dominant annual and perennial grasses of the Okavango Delta were isolated on N-free composite media and identified applying morphological and biochemical criteria and Restriction Fragment Length Polymorphism (RFLP). Azotobacter species were found associated mostly with the grasses Andropogon guyanus and Vetevaria nigritiana (103CFU g–1 rhizosphere soil). Annual grasses such as Eragrostis inamoena, Setaria sphacelata as well as perennials showed insignificant populations (<101CFU g–1 soil). On the contrary, Azospirillum spp. was found associated with most of the grasses. Highest population densities (above 104MPN g–1 soil) were observed in rhizospheres of E. inamoena, Cympogon excavatus, Sporobolus acinifolis, Eragrostis lapila and Eragrostis rigidor and lowest population densities (below 102MPN g–1 soil) in rhizospheres of Andropogon guyanus and Panicum repens. Flooding increased the Azotobacter populations, while Azospirillum spp. populations were significantly reduced. Nitrogen-fixing sulphur reducers were observed in the rhizosphere of annuals (A. guyanus and P. repens) and only in perennials growing in flooded soils. No Beijerinckia species were found associated with any of the grasses. The highest soil nitrogen levels were detected in flooded soils (<0.20% N) while no N was detected in the rhizosphere soil of grasses growing in very dry soils (<5% moisture content). The results indicate that in the Okavango Delta, total soil nitrogen varies with flooding regime. With flooding, the diazotroph population shifts towards Azotobacter and Nfixing sulphur reducers while Azospirillum spp. are widespread in non-flooded soils. RFLP analysis of the 1 450bp amplicon using the restriction endonuclease Alu1, showed three different banding profiles, suggesting the occurrence of three different species of Azospirillum. URI: http://hdl.handle.net/10311/294 Files in this item: 1
Flooding and its influence.pdf (2.253Mb) -
Gumbricht, T.; Wolski, P.; Frost, P.; McCarthy, T.S. (Elservier, www.elsevier.com, NaN, 2004)[more][less]
Abstract: The pristine Okavango Delta wetland of northern Botswana is potentially under threat due to water abstraction from its tributaries. We have developed a statistical model which makes it possible to predict the extent of wetland loss which will arise from water abstraction. The model also permits prediction of the maximum area of flooding, and its spatial distribution, three months in advance of the flood maximum. The model was calibrated using maximum areas of seasonal inundation extracted from satellite imagery covering the period 1985-2000, which were correlated with rainfall and total flood discharge. A technique was developed to translate the modelled flood area into a flood map. The methodology can predict maximum area of flooding and its distribution with better than 90% accuracy. An important, although relatively minor, source of error in the spatial distribution of the flood arises from a secular change in flood distribution in the distal Delta which has taken place over the last 15 years. Reconstruction of flooding history back to 1934 suggests that the Delta may be subject to a quasi 80 year climatic oscillation. If this oscillation continues, the extent of flooding will increase in the coining decades. URI: http://hdl.handle.net/10311/948 Files in this item: 1
Gumbricht JOH 2004.pdf (2.449Mb)