- To assess management implications, a model was used to simulate the response of Acacia karroo to a wide range of different climatic patterns and defoliation regimes. The model predicts that if poor growing conditions initiate growth later in spring than normal, total season growth and harvest is significantly reduced. In comparison, cooler overall temperatures throughout the season reduce growth less markedly. Results indicate that increasing the number of camps in a pastoral system increases the total amount of A. karroo that can be harvested. The model illustrates, in general terms, the limits and constraints of increasing the number of camps, varying the length of stay in each and varying the length of the rest period before the next occupation at different stocking rates. It also indicates the increases in A. karroo harvests that can be expected with different management strategies. The most important prediction of the model was the large increase in productivity that could be expected by sparing or very light use early in the growing season. Even if it is possible to reduce stock in times of drought, this was shown to be of very little benefit. 1990 Taylor & Francis Group, LLC.