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| Titel |
Topo-edaphic controls over woody plant biomass in South African savannas |
| VerfasserIn |
M. S. Colgan, G. P. Asner, S. R. Levick, R. E. Martin, O. A. Chadwick |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 5 ; Nr. 9, no. 5 (2012-05-23), S.1809-1821 |
| Datensatznummer |
250007031
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| Publikation (Nr.) |
 copernicus.org/bg-9-1809-2012.pdf |
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| Zusammenfassung |
| The distribution of woody biomass in savannas reflects spatial patterns
fundamental to ecosystem processes, such as water flow, competition, and
herbivory, and is a key contributor to savanna ecosystem services, such as
fuelwood supply. While total precipitation sets an upper bound on savanna
woody biomass, the extent to which substrate and terrain constrain trees and
shrubs below this maximum remains poorly understood, often occluded by
local-scale disturbances such as fire and trampling. Here we investigate the
role of hillslope topography and soil properties in controlling woody plant
aboveground biomass (AGB) in Kruger National Park, South Africa. Large-area
sampling with airborne Light Detection and Ranging (LiDAR) provided a means
to average across local-scale disturbances, revealing an unexpectedly linear
relationship between AGB and hillslope-position on basalts, where biomass
levels were lowest on crests, and linearly increased toward streams (R2 = 0.91). The observed pattern was different on granite substrates, where AGB
exhibited a strongly non-linear relationship with hillslope position: AGB
was high on crests, decreased midslope, and then increased near stream
channels (R2 = 0.87). Overall, we observed 5-to-8-fold lower AGB on
clayey, basalt-derived soil than on granites, and we suggest this is due to
herbivore-fire interactions rather than lower hydraulic conductivity or clay
shrinkage/swelling, as previously hypothesized. By mapping AGB within and
outside fire and herbivore exclosures, we found that basalt-derived soils
support tenfold higher AGB in the absence of fire and herbivory, suggesting
high clay content alone is not a proximal limitation on AGB. Understanding
how fire and herbivory contribute to AGB heterogeneity is critical to
predicting future savanna carbon storage under a changing climate. |
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