Browsing by Author "Ringrose, S."
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Moleele, N.; Ringrose, S.; Arnberg, W.; Lunden, B.; Vanderpost, C. (Taylor and Francis http://www.clas.ufl.edu/lueci/southworth/RS-class-advanced/Discussion-readings/Moleele%20et%20al%202001%20Assessment%20of%20veg%20indexes%20i.pdf, NaN, 2001)[more][less]
Abstract: Considerable signi® cance is placed on the mapping and monitoring of degraded areas in semi-arid regions of the world, including Botswana. Degraded areas include those suVering from bush encroachment, believed to result from heavy cattle grazing over a number of years. However, certain bush encroachment species have been found to be relatively nutrient-rich.The present work considers the extent to which a series of quanti® ed layers throughmainly bush encroachment canopies can be identi® ed using conventional and newly derived vegetation indexes and transforms based on Thematic Mapper (TM) imagery. Field work involved the strati® cation of green biomass into ® rstly the herbaceous cover layer; secondly the 0.3± 1.5m browse layer; then the 1.5± 2.5m browse layer; and ® nally the >2.5m browse layer. Biomass measurements from these layers were statistically associated with conventional vegetation indexes and transforms such as the NormalizedDiVerenceVegetation Index (NDVI), brightness and greenness values, and relatively newly derived darkening indexes involving the mid-infrared bands. When green biomass and transformed pixel data were averaged per classi® ed vegetation unit, weak negative correlations emerged between grass biomass and the transformed pixel data and no signi® cant correlations developed with the woody biomass (browse) layers. However, when point data were used in the analyses, results showed that most indexes and the brightness transform were signi® cantly correlated with the lower browse layer. Only the darkening indexes and brightness function were sensitive to the browse layers individually and the browse plus grass layers. This work shows the limitations of conventional indexes such as the NDVI in terms of browse and herbaceous layer assessment. New indexes for forage assessment based on relationships between the mid-infrared bands, such as those found in the new MODIS TERRA platform, are urgently required for semi-arid areas. URI: http://hdl.handle.net/10311/410 Files in this item: 1
Moleele_IJRS_2001.pdf (903.7Kb) -
Gobagoba, L.; Meyer, T.; Ringrose, S.; Kampunzu, A.B.; Coetzee, S. (Botswana Society, NaN, 2005)[more][less]
Abstract: Calcrete deposits of the Qangwa area, northwestern Botswana are evaluated on the basis of satellite imagery and sedimentological analysis. Enhanced Thematic Mapper imagery interpretation combined with field evidence has led to identification of the calcrete. This project aims at making a detailed surficial geology map accompanied by a report as a step in expanding the knowledge of calcretes. It also attempts to develop an understanding of the relationship in the timing of the late Quaternary wetter and drier phases. A digital map using GIS and remote sensing applications was developed from both analysed data and fieldwork. Data analysis revealed five types of calcretes and a calcareous soil. Hardpan calcrete along with brecciated and conglomeratic calcrete dominate the interfluves and are believed to predate the formation of nodular and honeycomb calcrete which occupy the valleys. The older hardpan associated types may have developed following regional wet/warm periods the last of which has been dated elsewhere as occurring c. 120,000. The younger valley calcretes show different mechanisms of formation, and are believed to have been developed following incision and palaeo-lake establishment, c. 25,000 years ago. URI: http://hdl.handle.net/10311/943 Files in this item: 1
Gobagoba 2005 calcrete mapping.pdf (2.409Mb) -
Huntsman-Mapila, P.; Kampunzu, A.B.; Ringrose, S.; Vink, B. (Elsevier www.elsevier.com/locate/sedgeo, NaN, 2005)[more][less]
Abstract: 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. URI: http://hdl.handle.net/10311/382 Files in this item: 1
Kampunzu2005OkavangoDeltasediments.pdf (1.941Mb) -
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) -
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) -
Aranibar, J.N.; Anderson, I.C.; Ringrose, S.; Macko, S.A. (Elsvier, www.elsevier.com, NaN, 2003)[more][less]
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 "non-crusty" soils under litter, moss, or sand. High values of 15N natural abundance (delta15N) indicated that processes other than N fixation were more important in the crusts than N fixation. For example, coupled and ammonia volatilization or atmospheric deposition of 15N-enriched nitrate or ammonium may have caused shifts in delta15N 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. URI: http://hdl.handle.net/10311/983 Files in this item: 1
Ringrose_Importance_of_Nitrogen_2003.pdf (2.069Mb) -
Ringrose, S.; Vanderpost, C.; Matheson, W.; Wolski, P.; Huntsman-Mapila, P.; Murray-Hudson, M.; Jellema, A. (Elsevier Ltd; www.elsevier.com/locate/jaridenv, January NaN, 2007)[more][less]
Abstract: This work seeks to determine whether riparian woody plant variables respond to drying and salinity regimes in the semi-arid distal Okavango Delta, northern Botswana. Structural and compositional variables were obtained from 47 field sites. Mapping using satellite imagery illustrated differences in the character of riparian zones in terms of species composition and provided data on flood frequency. Salinity data plots show increases downstream. Results imply that woody plant variables respond to desiccation-driven change due to water-table lowering (reduced recharge) and increased salinization through distinct changes in tree and shrub height, plant density and species richness. In the wetter, intermediate distributaries, key biotic indicators of ecosystem change comprise structural variables such as decreases in canopy cover per cent and tree height and increases of shrub height, which are indicative of mainly ground-water declines. Biotic indicators in the less frequently flooded receiver channels comprise plant density and species richness increases involving mainly brackish ground-water-tolerant and dryland species which are indicative of both ground-water declines and/or salinization. These indicators could provide useful parameters for use in long- and short-term monitoring aimed at assessing desiccation-driven change in different parts of the Okavango Delta and possibly other semi-arid wetlands. The indicators are important as a less-expensive alternative to drilling as a means of verifying ground-water declines and/or salinization. URI: http://hdl.handle.net/10311/161 Files in this item: 2
license.txt (1.998Kb)Ringrose_et_al_JAE_07.pdf (1.322Mb) -
Meck, M.L.; Atlhopheng, J.; Masamba, W.R.L.; Ringrose, S.; Diskin, S. (Bentham Open, http://www.benthamscience.com/open/tomj/index.htm, NaN, 2011)[more][less]
Abstract: This study set out to establish the major minerals at Dorowa and determine which of those are likely to host metals that may leach into surface and groundwater. This study comes after a preliminary assessment of the water quality in the Save River downstream of the Dorowa phosphate mine in Zimbabwe showed an increase in conductivity, iron content, manganese content, nitrates and hardness when compared to those taken before the mining area. X-Ray Diffractometry (XRD) was used to establish the major minerals at Dorowa whilst Inductively Coupled Plasma Mass Spectrometry (ICP- MS) was used to establish the chemistry of the rocks. The results from this study show that the major minerals in the rocks around Dorowa are feldspars, pyroxenes, apatite, magnetite and calcite. The metals hosted by the rocks include Ag, As, Be, Cd, Co, Cu, Pb, Hg, Ni, Sb, Se and Zn. The study concludes that the minerals likely to host metals are calcite and apatite. Metal hosting is higher in apatite minerals than in calcite. Metal hosting by the other minerals observed in the study area is low. URI: http://hdl.handle.net/10311/1109 Files in this item: 1
Atlhopheng_OMJ_2011.pdf (848.6Kb) -
Meck, M.; Atlhopheng, J.; Masamba, W.; Ringrose, S.; Diskin, S. (Bentham Open, NaN, 2010)[more][less]
Abstract: This study set out to establish the major minerals at Dorowa and determine which of those are likely to host metals that may leach into surface and groundwater. This study comes after a preliminary assessment of the water quality in the Save River downstream of the Dorowa phosphate mine in Zimbabwe showed an increase in conductivity, iron content, manganese content, nitrates and hardness when compared to those taken before the mining area. X-Ray Diffractometry (XRD) was used to establish the major minerals at Dorowa whilst Inductively Coupled Plasma Mass Spectrometry (ICP- MS) was used to establish the chemistry of the rocks. The results from this study show that the major minerals in the rocks around Dorowa are feldspars, pyroxenes, apatite, magnetite and calcite. The metals hosted by the rocks include Ag, As, Be, Cd, Co, Cu, Pb, Hg, Ni, Sb, Se and Zn. The study concludes that the minerals likely to host metals are calcite and apatite. Metal hosting is higher in apatite minerals than in calcite. Metal hosting by the other minerals observed in the study area is low. URI: http://hdl.handle.net/10311/932 Files in this item: 1
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Moleele, N.M.; Ringrose, S.; Matheson, W.; Vanderpost, C. (ScienceDirect, www.sciencedirect.com, NaN, 2002)[more][less]
Abstract: the cattle-dominated grazing areas of Botswana. Bush encroachment species – for instance Acacia tortilis, A. erubescens, A. mellifera, Dichrostachys cinerea, Grewia flava, and Terminalia sericea –are increasing in cover and density around foci points (e.g. water points and kraals) at the expense of the grass cover. A number of factors have the effect of encouraging the germination and survival of bush encroachment species. The practice of cattle husbandry and continual shifting of foci points within grazing areas have resulted in the spread of the distribution of bush encroachment species across the country. This is evidenced by the potential extent of 37 000 km2 (6 4% of Botswana) of darkened and near infrared (NIR) reflective bush encroached areas in 1994. This paper suggests that specific management strategies should be adopted to help overcome the bush encroachment problem, which is causing a significant reduction in the extent of Botswana’s high quality rangeland. These strategies may vary from the enforced reduction of grazing intensity in areas identified as being heavily bush encroached to the selective management of opportunistic (communal) grazing in better quality predominantly grassland areas. Further work is however required to update this analysis and especially to consider trends since 1994–1995. While some work on the extent of woody cover and the further causes of bush encroachment is being undertaken under the SAFARI2000 project, more research is needed in specific areas to pinpoint causes and responses to the bush encroachment problem. URI: http://hdl.handle.net/10311/985 Files in this item: 1
Moleele_ et al_More_Woody_2002.pdf (3.119Mb) -
Meck, M.L.; Masamba, W.R.L.; Atlhopheng, J.; Ringrose, S. (Elsevier Science Ltd, http://www.elsevier.com/locate/pce, NaN, 2011)[more][less]
Abstract: The objective of the study was to investigate the role played by the natural environment in protecting the transboundary Save River from the impacts of metals derived from phosphate mining at Dorowa. The study is a follow up study from a previous one that noted that there is natural attenuation at Dorowa. Water and sediment samples were collected in the Save River and the streams that drain the Dorowa dumps. Inductively coupled plasma mass spectrometry (ICP–MS) was used to analyze the cations (Na+, K+, Ca2+, Mg2+, Cu2+, Co2+, Fe2+, Ni2+, Zn2+, Pb2+, Sn2+, Mn2+, Cd2+) in the samples. Major anions Cl , SO2 4 and NO 3 were analyzed by standard chromatography whilst CO2 3 and HCO 3 were determined by titration. pH was measured on site. Geochemical modeling of the water composition was conducted with Visual Minteq. The results show that natural attenuation is being achieved through precipitation of solids from the water and subsequent deposition onto the sediments. Six of the metals are almost completely precipitated (Cu 99.99%, Fe 99.39%, Ni 91.24%, Pb 99.87%, Sn 99.99% and Zn 88.66%). However Mn, Co and Cd remain in solution. Thus the natural environment is protecting the Save River which is a transboundary river from the impacts of mining through precipitation of the metals. Users downstream of Dorowa mine are therefore not being affected by mining pollution. This study demonstrates that besides being a legitimate and important user of water, the natural environment can also play a significant role in protecting water quality by attenuating metals naturally. By analyzing costs incurred in several places where alternative methods are employed to remediate metal related pollution the study concludes that natural remediation at Dorowa is saving the nation in environmental costs. Therefore the paper advocates for appreciation of the role that the natural environment plays in protecting ecosystems from the impact of human developments and environmental costs. Subsequently, this calls for recognition of natural environment’s role in water resources management for the sustenance of ecosystems and peoples livelihoods. URI: http://hdl.handle.net/10311/963 Files in this item: 1
Atlhopheng_PCE_2011.pdf (630.3Kb) -
O'Halloran, L.; Shugart, H.; Wang, L.; Caylor, K.; Ringrose, S.; Kgope, B. (Elsevier, February 19, 2010)[more][less]
Abstract: The Kalahari Transect (KT) is an International Geosphere–Biosphere Programme mega-transect designed to examine hydrological and ecological patterns and processes throughout the savannas of southern Africa. The KT traverses a precipitation gradient ranging from w920 mm rain/year in the north to w260 mm rain/year in the south. Previous research shows a positive correlation between canopy cover and precipitation suggesting a water limitation on productivity. However, there has been minimal research on other possible sources of limitations, such as soil Nitrogen (N) and/or Phosphorus (P). We used a factorial in-situ experimental design to test for increased aboveground grass production (measured as peak season standing stock) under elevated soil P and Pþ N levels. Four sites along the KT precipitation gradient were used in this study: Mongu (Zambia), Pandamatenga (Botswana), Ghanzi (Botswana) and Tshane (Botswana). Soils at each site were amended with N and P fertilizers during the dry season. We extracted soil samples during the following growing season to analyze for plant available soil P. Vegetation samples were harvested from which we measured foliar P and aboveground grass biomass production. We saw differences in foliar P at the treatment and site level but not for the interaction between treatment and site. There were individual effects from site on biomass but not for any interactions with nutrient treatments. Despite higher levels of foliar P, we did not detect an increase in aboveground biomass. This may be explained by luxury uptake or allocation to below ground resources. URI: http://hdl.handle.net/10311/797 Files in this item: 1
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Kgathi, D.L.; Kniveton, D.; Ringrose, S.; Turton, A.R.; Vanderpost, C.; Lundqvist, J.; Seely, M. (Elsevier; www.elsevier.com/locate/jhydrol, NaN, 2006)[more][less]
Abstract: The Okavango basin comprises the Cuito and Cubango active catchment areas in Angola, in addition to the Kavango's Okavango non-active catchment in northern Namibia and Botswana. The Okavango River water and its ecosystem resources are critically important sources of livelihoods for people in the basin. Pressures from livelihoods and development are already impacting on the environment. These pressures may increase in the future due to the rapid increase in population, the peace process and associated resettlement activities in Angola, and major development initiatives in Botswana and Namibia. For instance, possible future increase in water abstraction from the Okavango River may affect the long-term environmental sustainability of the Okavango Delta by minimizing channel shifting and thereby reducing spatial biodiversity. The paper argues that while conservation of the natural environment is critical, the pressing development needs must be recognized. The reduction of poverty within the basin should be addressed in order to alleviate adverse effects on the environment. The paper recommends that the development of sustainable tourism and community-based natural resource management initiatives may be appropriate strategies for reaching the Millennium Development Goals of poverty alleviation and achievement of environmental sustainability in the Okavango Basin. These initiatives have a comparative advantage in this area as demonstrated by the performance of the existing projects. URI: http://hdl.handle.net/10311/154 Files in this item: 2
kgathi_j_hydrology_2006.pdf (6.004Mb)license.txt (1.998Kb) -
Ringrose, S.; Kampunzu, A.B.; Vink, B.W.; Matheson, W.; Downey, W.S. (John Wiley & Sons, Ltd. http://www3.interscience.wiley.com/journal/117935722/grouphome/home.html, NaN, 2002)[more][less]
Abstract: Quaternary sedimentation in the Moshaweng dry valley of southeastern Botswana is evaluated on the basis of geomorphological evolution and sedimentological analyses. Stratigraphic evidence reveals an 'upper surface (1095 m) containing abundant sil-calcrete, an intermediate surface (1085 m) in which sil-calcrete underlies nodular calcrete and lower (1075 m) surface in which sil-calcrete and nodular calcrete are interbedded. This subdivision is reflected in the geochemical composition of the sediments which show an overall trend of decreasing Si02 content (and increasing CaC03 content) with depth from the highest to the lowest surface levels. The calcretes and sil-calcretes represent modifications of pre-existing detrital Kalahari Group sand and basal Kalahari pebbles which thinned over a Karoo bedrock high. Modification took place during wet periods when abundant Ca++ -rich groundwater flowed along the structurally aligned valley system. With the onset of drier conditions, water table fluctuations led to the precipitation of nodular calcretes in the phreatic layer to a depth of about 20 m. A major geochemical change resulted in the preferential silicification of the nodular calcrete deposits. Conditions for silica mobilization may be related to drying-induced salinity and in situ geochemical differentiation brought about by pebble dissociation towards the top of the sediment pile. As calcretization and valley formation progressed to lower levels, silica release took place on a diminishing scale. Thermoluminescence dating infers a mid-Pleistocene age for sil-calcrete formation suggesting that valley evolution and original calcrete precipitation are much older. Late st~ge dissolution of CaC03 from pre-existing surface calcretes or sil-calcretes led to the formation of pedogenic case-hardened deposits during a time of reduced flow through the Moshaweng system possibly during the upper or late Pleistocene. URI: http://hdl.handle.net/10311/310 Files in this item: 1
Ringrose_ESPL_2002.pdf (3.095Mb) -
Ringrose, S.; Harris, C.; Huntsman-Mapila, P.; Vink, B.W.; Diskins, S.; Vanderpost, C.; Matheson, W. (Elsevier www.elsevier.com/locate/sedgeo, NaN, 2009)[more][less]
Abstract: Trace elements togetherwith some O and C isotope analysiswere undertaken on duricrust strandline deposits in the palaeo-Makgadikgadi sub-basin (PMSB) to provide insight into palaeo-climatic conditions through the interpretation of calcrete, silcrete–calcrete intergrade and silcrete deposits. Trace element content and relative abundance suggest that the duricrust origins are associated with the long-term weathering of the Karoo Large Igneous Province which underlies the PMSB. This work shows that duricrust origins are related to Ca2+ and Si (and associated trace elements) being transported mainly through the groundwater and then subsequently precipitated at different strandline elevations over time. Local groundwater feeding in towards the pan margin and accumulating in near-neutral pan-marginal pools, appears to facilitate Si concentration and permeation of pre-existing calcretes. The silica precipitates as the pH drops when renewed freshwater enters the pools. Hence the inferred palaeo-climatic regime for silcretisationmay be similar to that occurring in Botswana at present being dry semi-arid with lowseasonal rainfall. In contrast the extensive calcrete precipitation in the strandlines results from abundant Ca2+ in adjacent waters which appear to be derived from both local and regional sources. The arrival of Ca2+ from regional sources (shown by trace element evidence) infers heavy rainfall in the upper catchment suggesting a major humid event followed by regional drying. Palaeo-climatic inferences suggest the juxtaposition ofmajor humid events interspersedwithmore normal semi-arid palaeo-climateswith an exception obtained from isotope data, of drier and cooler conditions than usual for the region around 80–90000 years ago. Whereas trace element data can greatly assist in the interpretation of complex deposits such as duricrusts, care should be taken over the use of particular ratios (such as Yb/Gd ratio) which may produce spurious results. URI: http://hdl.handle.net/10311/560 Files in this item: 1
RINGROSE2009Makgadikgadi Pans.pdf (3.500Mb) -
Meck, M.L.; Atlhopheng, J.; Masamba, W.R.L.; Ringrose, S. (Elsevier. http://www.elsevier.com, August 20, 2010)[more][less]
Abstract: The study set out to determine the weathering and dissolution of metal hosting minerals at Dorowa for purposes of deducing pollution potential to the nearby Save River. Phosphate rock is mined at Dorowa for the production of phosphate fertilizer. The major minerals found in the ring complex are feldspars, pyroxenes, apatite, magnetite and calcite. Chemical analysis established that the rocks are associated with metals that include copper, lead, zinc, cobalt, nickel, tin and cadmium. Among the many minerals present apatite and calcite host metals more than the other minerals due to their crystal structure. This study investigated the weathering and dissolution of these two minerals. Both apatite and calcite dissolve in natural environmental conditions prevalent at Dorowa. From the analysis the study concludes that the potential availability of metals trapped in the calcite and apatite structures is high. The understanding of weathering and dissolution of metal hosting minerals is important in predicting quality of water around the study area, because most villagers use the Save River as their primary drinking water source. URI: http://hdl.handle.net/10311/833 Files in this item: 1
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Meck, M.L.; Atlhopheng, J.; Masamba, W.R.L.; Ringrose, S. (Elsevier Science Ltd, http://www.elsevier.com/locate/pce, NaN, 2010)[more][less]
Abstract: The study set out to determine the weathering and dissolution of metal hosting minerals at Dorowa for purposes of deducing pollution potential to the nearby Save River. Phosphate rock is mined at Dorowa for the production of phosphate fertilizer. The major minerals found in the ring complex are feldspars, pyroxenes, apatite, magnetite and calcite. Chemical analysis established that the rocks are associated with metals that include copper, lead, zinc, cobalt, nickel, tin and cadmium. Among the many minerals present apatite and calcite host metals more than the other minerals due to their crystal structure. This study investigated the weathering and dissolution of these two minerals. Both apatite and calcite dissolve in natural environmental conditions prevalent at Dorowa. From the analysis the study concludes that the potential availability of metals trapped in the calcite and apatite structures is high. The understanding of weathering and dissolution of metal hosting minerals is important in predicting quality of water around the study area, because most villagers use the Save River as their primary drinking water source. URI: http://hdl.handle.net/10311/1021 Files in this item: 1
Atlhopheng_PCE_2010.pdf (758.1Kb) -
VanderPost, C.; Ringrose, S.; Seely, M. (Botswana Society, NaN, 2005)[more][less]
Abstract: Image processing in the upper Okavango catchment resulted in ten generalised classes which may be used as base line data for monitoring future overall land-use/cover change assessments over the entire upper catchment. Specific work was undertaken using single images for more detailed land-use/cover mapping in a 10 km buffer along all tributaries of the upper Okavango in Angola and Namibia. In terms of the under-developed Angolan upper catchment there is relatively little land clearing at present, and impacts on water use and quality are expected to be minimal in the near future. This is a consequence of 20 years of civil war, while the return of refugees is being inhibited by the prevalence of land-mines. Much more extensive development is taking place in Namibia along the southern bank of the Kavango river. This area is likely to become more intensively used as Namibia attempts to develop greater food security. Further work is required to monitor the impacts from Namibian agricultural expansion. These are likely to be pervasive in terms of the ecology of both the Mahango Game Reserve in Namibia and the Okavango Delta in Botswana. URI: http://hdl.handle.net/10311/936 Files in this item: 1
VanderPost 2005 Prelim.pdf (2.370Mb) -
Caylor, K.K.; Dowty, P.R.; Shugart, H.H.; Ringrose, S. (November 23, 2011)[more][less]
Abstract: The observed variability in vegetation structure within landscapes was used as the basis for model estimates of the range of annual productivity of landscape patches at four sites along a moisture gradient in southern Africa ranging from 879 to 365 mm mean annual rainfall. Principal components of patch-scale variability in leaf area, woody biomass and vertical leaf profiles were derived from intensive characterization of the small-scale spatial structure of woody vegetation at each site. For each site, the mean and extremes of the principal component distribution parameterized an ecophysiology model of vegetation productivity. Vegetation was most heterogeneous at intermediate locations along the rainfall gradient. Variability in vegetation structure led to a range of annual productivity within one site (600 mm) that accounted for 68% of the total range in mean productivity across all sites. Patch-scale estimates of tree productivity were found to be primarily correlated to annual rainfall (r2=0.66, P=0.001) and not woody leaf area (r2=0.01, P=0.75), while grass productivity was found to be related to values of woody leaf area (r2=0.77, P<0.001) and not annual rainfall (r2=0.11, P=0.29). This result indicates that life-form interactions have a significant role in controlling vegetation productivity across the rainfall gradient. The findings of this study emphasize the importance of considering heterogeneity rather than mean structure when modeling productivity, particularly when considering dynamic vegetation structure, where differences between landscape patches may not be well represented in the mean structure. URI: http://hdl.handle.net/10311/933 Files in this item: 1
Caylor Ringrose 2004.pdf (1.770Mb) -
Neuenschwander, A.L.; Crawford, M.M.; Ringrose, S. (Taylor & Francis; http://www.tandf.co.uk/journals/titles/01431161.asp, October NaN, 2005)[more][less]
Abstract: The Earth Observing-1 (EO-1) satellite acquired a sequence of data in 2001 and 2002 that highlighted the annual flooding of the lower Okavango Delta. The data were collected as part of the calibration/validation programme for the Advanced Land Imager (ALI) sensor on the NASA EO-1 satellite. The primary purpose of this study was to compare the capability of ALI to that of Landsat ETM+ for large-scale mapping applications in the Okavango Delta. While the extent and inaccessibility of many areas of the Delta make application of remote sensing attractive, the availability of data with adequate spatial and spectral resolution has limited the characterization of the complex patterns of land cover and geomorphology in the Delta. Initial analysis of the ALI data via supervised classification clearly showed macro-flood features, delineation of downstream channel flow areas, and lateral-downstream inundation of the floodplain. These patterns and the proportions of flooding of the channel compared to that of the floodplain (impoundment) varied annually, from the wetter seasonal swamps through the drier seasonal and occasional swamps. Consistently higher classification accuracies achieved using ALI data relative to ETM+ data are attributed to the higher signal-to-noise ratio and the increased dynamic range of the ALI data. URI: http://hdl.handle.net/10311/169 Files in this item: 2
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