Browsing Okavango Research Institute (ORI) by Subject "Kalahari"

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Groundwater investigation in semi-arid developing countries, using simple GIS tools to facilitate interdisciplinary decision making under poorly mapped conditions: The Boteti area of the Kalahari region in Botswana

VanderPost, C.; McFarlane, M. (Elsevier www.elsevier.com/locate/jag, NaN, 2007)

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Abstract:

Locating additional long-term groundwater resources in semi-arid regions of developing countries with growing populations is an expensive undertaking. Simple geographic information system (GIS) techniques can be utilised to facilitate efficient application of expensive geophysical techniques and test-drilling by functioning as an interdisciplinary integration and decision-making tool, especially in data-poor and poorly mapped environments where more sophisticated GIS techniques are not applicable. The paper demonstrates this in the context of the search for groundwater alternatives to the dwindling river water supply in the Boteti area of the Kalahari region in Botswana.

URI:

http://hdl.handle.net/10311/573

Files in this item: 1

VanderPost2007GroundwaterInvestigation.pdf (3.243Mb)

Importance of nitrogen fixation in soil crusts of southern African arid ecosystems: acetylene reduction and stable isotope studies

Aranibar, J.N.; Anderson, I.C.; Ringrose, S.; Macko, S.A. (Elsvier, www.elsevier.com, NaN, 2003)

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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)

Looking for progenitors: a molecular approach to finding the origins of an invasive weed

Bond, J.M.; Veenedaal, E.M.; Hornby, D.D.; Gray, A.J. (Kluwer Academic Publishers, http://www.springerlink.com, November 28, 2002)

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Abstract:

One of the major problems in determining the origin of invasive species is that often their arrival is unnoticed. Only when population levels increase is their presence noticed but by this time determining the point of arrival is confounded by the extensive spread of the species. Here we use molecular markers (ISSRs) to determine the origin of an invasive weed in the Kalahari region, a species for which several origins could be possible. We show that molecular markers can be useful tools in determining the origin of invasive species.

URI:

http://hdl.handle.net/10311/1025

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Bond_2002.pdf (2.049Mb)

Nutrient limitations on aboveground grass production in four savanna types along the Kalahari Transect

O'Halloran, L.; Shugart, H.; Wang, L.; Caylor, K.; Ringrose, S.; Kgope, B. (Elsevier, February 19, 2010)

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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

Nutrient limita ... alahari Transect.doccx.pdf (674.4Kb)

Woody vegetation resource changes around selected settlement along aridity gradient in the Kalahari, Botswana

Sekhwela, M.B.M. (Elsevier Science Ltd, http://www.elsevier.com/locate/cag, July 22, 2002)

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Abstract:

This paper investigated changes in economically important woody vegetation resources around seven settlements located along an aridity gradient in the Kalahari. Available data at different rainfall levels were analysed for different vegetation aspects. Total woody plant density and number of species at each site increased with increasing rainfall level, while individual species density differed at each site irrespective of rainfall, due to other factors, for example, land use as indicated by high stump densities around old and high population settlements. Drought resulted in high mortality of certain species, increasing availability of fuelwood resource in the form of dead wood. However, prolonged drought from climatic changes could result in browse shortage, a vital resource in the Kalahari. There was generally low wood resource availability throughout the studied gradient, without any distinct relation to rainfall, reflecting the influence of other factors such as soils, land use and natural variability.

URI:

http://hdl.handle.net/10311/1024

Files in this item: 1

Sekhwela M.B.M_2002.pdf (552.9Kb)

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Browsing Okavango Research Institute (ORI) by Subject "Kalahari"

Browsing Okavango Research Institute (ORI) by Subject "Kalahari"

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