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| Titel |
Integrating hydrology and biogeochemistry in drylands: the Kalahari Transect as a model ecosystem |
| VerfasserIn |
L. Wang, K. Caylor, S. Macko, H. Shugart |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250021849
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| Zusammenfassung |
| In dryland ecosystems patterns of both nutrient and water availability limit the spatial and
temporal dynamics of plant growth. Traditionally, water and nutrient (e.g., nitrogen) have
been explored separately in terms of the individual constraints they place on ecosystem
function within water-limited ecosystems. We demonstrate that integrating hydrology and
biogeochemistry in arid environments leads to better understanding of ecosystem patterns and
processes across a wide range of dryland environments. Our presentation is based on the
synthesis of a set of extensive field data and experiments on soil biogeochemistry (e.g., soil
available nutrient concentrations, soil isotope compositions), hydrological parameters (e.g.,
soil moisture, rainfall) and vegetation structure (e.g., tree heights, tree spacing distances)
from a homogenous mega-transect (the Kalahari Transect) in southern Africa, The synthesis
shows that water availability determines nitrogen availability across regional rainfall
gradients, but that these patterns are strongly mediated at local scale by vegetation
patchiness, which plays an important role in nitrogen re-distribution and availability.
In addition, we show that both water and nitrogen availability contribute to the
maintenance of tree/grass composition within dryland ecosystems. Specifically, the
consistently higher foliar δ15N and lower soil δ15N of C3 plants compared to C4 plants
suggests that C4 plants are superior competitors for nitrogen, while differing C3
and C4 foliar δ13C relationships with rainfall for C3 plants and C4 plants indicates
that C3 plants are superior competitors for water. Finally, we show that spatial and
temporal patterns of water availability determine the forms of nitrogen dominance
with impacts on subsequent plant adaptations. Our synthesis demonstrates that
integrating ecohydrological and biogeochemistry observations are necessary to provide
holistic views of the complex processes governing dynamics of dryland ecosystems. |
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