We applied the technique developed by Flores-Flores and Yeaton (2000). This compares the asymmetry or distortion of canopies of trees that are growing in association with one another by means of an index,the coefficient of tree symmetry (TS) that indicates which individual of a pair of contiguous trees is competing more successfully for light.

We investigated the potential of an invasive alien tree to transform vegetation by quantifying the relative abilities of the alien tree Schinus molle and dominant native trees Acacia tortilis and Rhus lancea to compete for light when growing in association within a South African semi-arid savanna.