Hydrological and Nutrient Controls on the Structure and Function of Southern African Savannas K.K. Caylor, Paolo D’Odorico, Christelle Hély, Greg Okin, S.A. Macko, Natalie Mladenov, Lydia Ries, Susan Ringrose, T.M. Scanlon, H.H. Shugart, R.J. Swap, Matt Therrell, Lixin Wang and Robert Washington-Allen

Kalahari Transect Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation

Kalahari Transect Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation Detailed soil characterizations

Kalahari Transect Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation Detailed soil characterizations Instrumented long-term physical data records

Kalahari Transect Wet and dry season field campaigns for basic ecological process and detailed structural measurements of vegetation Detailed soil characterizations Instrumented long-term physical data records Field fertilization experiments with phosphorus and nitrogen and stable isotope analysis in experimental and spatially distributed contexts

Strong rainfall gradient, seasonal climate Uniform sandy soils – ‘Kalahari sands’ Heterogeneous vegetation; tree, shrub and grass in woodland, savanna, and shrubland mixtures. High net plant productivity, widespread biomass burning, high carbon turnover IGBP Kalahari Transect

Mean annual rainfall along the Kalahari Transect

Kalahari Rainfall –

Vegetation Patterns on the Kalahari Transect

Plant interactions dominate pattern Landscape interactions dominate pattern Spatial Variation in NDVI at Different Spatial Scales

Pattern and Process

Vegetation structural characteristics along the Kalahari Transect More Southerly and Drier Decreasing Tree Cover Grass Cover

Dispersed Clumped Depends on the Prior History

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A Landscape Vegetation Model Leaf Patch Multi-Patch Structure

UMD Tree Cover Data

Live Non-woody Live Tree Leaves Dead Non-woody Dead Tree Leaves

Could you tell me again where we’re going with all this?

Leaf Patch Multi-Patch Structure Regional Emissions to the Atmosphere or

WildfiresIndustrial Domestic Along with wildfires, there are other significant sources of emissions to the atmosphere.

WildfiresIndustrial Domestic We have some understanding of the contribution of these different sources.

WildfiresIndustrial Domestic Regional Emissions Transport Deposition

Live Non-woody Live Tree Leaves Dead Non-woody Dead Tree Leaves

Does this have any practical implications?

Grazing Pressure across Southern Africa

Grazing Impact across Southern Africa during a Wet Year.

Grazing Impact across Southern Africa in a Dry Year.

In wet versus dry years, the impact varies regionally Wet Dry

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