Simulating browse production and response of Acacia karroo to defoliation. I. Model discription and sensitivity analyses.

The model is aimed at synthesizing existing data to enhance the understanding of this data and explore the consequences of possible browse management strategies. It gives a good reproduction of the shoot and leaf growth responses used to develop it and a reasonable prediction of leaf growth when tested against independent data. The prediction of shoot growth against independent data was poor. Sensitivity analysis indicate that five parameters have a very strong influence on the output of the model. These are moisture, soil depth, the magnitude and duration of growth stimulation following defoliation, how soon growth is initialized and how favourable growing conditions are in spring. Plant size and the carry-over of growth stimulation from one year to the next had a moderate influence.Keywords: acacia karroo; browse production; defoliation; eastern cape; goats; growth response; growth stimulation; leaf growth; leaves; management strategy; model; sensitivity analysis; shoot growth; simulation model; soil depth; south afric