Relative performance of clumped vs. experimentally isolated plants in a South African winter-rainfall desert community
We conducted a factorial removal experiment in the arid strandveld on the west coast of South Africa to test the hypothesis that perennial species with a "preference" for occurring in multi-species clumps should derive benefits from their association into clumps. Contrary to our hypothesis, we obtained evidence of competition for water in the clumped non-succulent species studied in the form of depressed water potentials. We were not able to detect any effect on leaf water contents associated with isolation, suggesting that clumped plants are able to compensate physiologically in response to competitive stress. We also found that isolating individuals had no effect (positive or negative) on branch growth. Finally, we showed that isolating individuals exposed them to a far greater risk of damage by wind or animals. In light of these results we conclude that the spatial arrangement of plants in this community does suggest a situation where the benefits associated with occurring in clumps exceed any competitive costs.