20 research outputs found
Evaluating Ecohydrological Theories of Woody Root Distribution in the Kalahari
The contribution of savannas to global carbon storage is poorly understood, in part due to lack of knowledge of the amount of belowground biomass. In these ecosystems, the coexistence of woody and herbaceous life forms is often explained on the basis of belowground interactions among roots. However, the distribution of root biomass in savannas has seldom been investigated, and the dependence of root biomass on rainfall regime remains unclear, particularly for woody plants. Here we investigate patterns of belowground woody biomass along a rainfall gradient in the Kalahari of southern Africa, a region with consistent sandy soils. We test the hypotheses that (1) the root depth increases with mean annual precipitation (root optimality and plant hydrotropism hypothesis), and (2) the root-to-shoot ratio increases with decreasing mean annual rainfall (functional equilibrium hypothesis). Both hypotheses have been previously assessed for herbaceous vegetation using global root data sets. Our data do not support these hypotheses for the case of woody plants in savannas. We find that in the Kalahari, the root profiles of woody plants do not become deeper with increasing mean annual precipitation, whereas the root-to-shoot ratios decrease along a gradient of increasing aridity
Fire‐induced albedo change and surface radiative forcing in sub‐Saharan Africa savanna ecosystems: Implications for the energy balance
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On the effects of wildfires on precipitation in Southern Africa
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On the effects of wildfires on precipitation in Southern Africa
Appendix C. Individual statistics for excavated trees.
Individual statistics for excavated trees
Appendix B. Extrapolation procedure for missing roots.
Extrapolation procedure for missing roots
Left: Fire frequency from 2000 to 2011 calculated from the MODIS Burned Area Product (MCD45) [<b>72</b>] in yr<sup>−1</sup>.
<p>White areas experienced no fires during this period. Right: Average fire frequency (in yr<sup>−1</sup>) calculated along a longitudinal transect (21.3°) using a moving box of approximately 100×100 km.</p
Coordinates, mean annual precipitation (MAP), and plant community composition of the study sites.
<p>Information on precipitation includes mean annual precipitation (MAP) ± the standard deviation of annual precipitation and (in parentheses) the minimum annual precipitation recorded in 1971–2006. Because rainfall data from Kuke do not exist, the values reported are from Ghanzi.</p
Root diameter distribution along the soil profile across the Kalahari's rainfall gradient.
<p>The error bars indicate the minimum and maximum data values, unless outliers are present (shown as circles). The black line indicates the median, while the box boundaries are the lower and upper quartiles. Based on a set of 60 soil profiles sampled at each site.</p