Rangeland production: use of models incorporating aggregated knowledge and fuzzy construction

This work reports on a method using fuzzy membership functions to construct an aggregated interaction matrix in which the summation of variables is scaled according to the way rainfall and soil variables affect water availability to plants and hence influence rangeland productivity. Aggregation of the variables gives a comprehensive value which can be used to predict production. The model increases the predictability of production to 81% compared to models using rainfall alone and a multiplicative parametric one which give predictabilities of 61 and 67% respectively. The results showed that (1) the importance of rainfall in determining production was most important at lower rainfalls i.e. < 350 mm; (2) soil texture and particularly slope were important throughout the rainfall range (149–700 mm) investigated; and (3) soil depth was only important at the higher > 350 mm rainfalls. The aggregated interaction matrix gives a measure of land productive capability.