IDESSA

IDESSA

The increase in density of the woody savanna component is a common form of land degradation in South Africa with serious ecological and economic implications. The tree-grass ratio is determined by a range of interacting factors such as herbivory, fire and rainfall. Certain spatial and temporal combinations of these factors result in the suppression of the grass layer and promotion of woody growth. Related dynamics can be intensified by the regionally increasing atmospheric CO2-levels, which lead to competitive advantages of C3- over C4-plants. If land management does not accommodate these complex interrelated effects, savanna ecosystems loose resilience with a poorly reversible decrease in ecosystem functioning and productivity. At this stage, natural self-thinning processes as part of cyclical succession between open savanna and woody dominance are far beyond an economically feasible time horizon. Land-use practices to mitigate an increase in density of woody plants such as sophisticated spatio-temporal distribution of livestock or game, flexible stocking rates or prescribed burning may be ineffectual, and expensive chemical, mechanical or manual technologies need to be applied to control dense woody stands.

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Maximilian H.K. Hesselbarth
Computational ecologist

Ecological Modelling

Publications