Original Articles

A drought assessment model for Karoo rangeland

Published in: South African Journal of Plant and Soil
Volume 19, issue 2, 2002 , pages: 93–98
DOI: 10.1080/02571862.2002.10634445
Author(s): J.C. Venter, Republic of South Africa


The KAROO drought assessment model simplifies veld growth responses to rainfall variability by simulation of the growth and dieback of a hypothetical plant species. Soil water content is treated as a simple weighting factor which determines the plant's growth rate as a weighted average of two basic growth rates, viz. those under well- watered and dry soil conditions. Multiple growth stages of variable extent are postulated on the basis of evolutionary forcing by Karoo rainfall patterns. The model was fitted to growth data of a Karoo dwarf shrub species, assuming three growth stages which are initiated when the annual growth equals 0 (on day 1), 3 and 50% of that of an equivalent, well-watered plant. The averaging of basic growth rates needs further investigation in order to better simulate compensatory growth after drought.

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