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 – 1901-1996
Kalahari Rainfall – 1901-1996
Kalahari Rainfall – 1901-1996
Kalahari Rainfall – 1901-1996
Kalahari Rainfall – 1901-1996
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
DecreasingTree Cover
Grass Cover
Dispersed
Clumped
Depends on the
Prior History
is not equivalent to vnecessarily
A Landscape Vegetation Model
LeafPatch
Multi-Patch Structure
UMD Tree Cover Data
LiveNon-woody
LiveTree
Leaves
DeadNon-woody
DeadTree
Leaves
Could you tell me again where we’re going with
all this?
LeafPatch
Multi-Patch Structure
Regional Emissionsto 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
LiveNon-woody
LiveTree
Leaves
DeadNon-woody
DeadTree
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
is not equivalent to vnecessarily