The horizontal distribution of root biomass in a South African winter-rainfall desert community

Abstract

We address the question of whether the spatial distribution of root biomass mirrors the highly clumped distribution of shoot biomass in two desert plant communities (short and medium strandveld) on the west coast of South Africa. Results indicate that this is generally not the case. In both communities, there was no significant difference between the fine root (< 2 mm diameter) biomass under clumps compared with gaps between clumps. In the short strandveld, this was also the case for structural root mass. The only exception to this general trend was in the case of structural roots in the medium strandveld where there was more biomass under vegetation clumps. These patterns suggest that strandveld plants are shaped by the trade off between advantages of clumping and the inevitable competition for water that this association brings. In these communities, the competitive disadvantages of clumping above-ground may be offset by root foraging between clumps. Fertile islands do not seem to be a feature of these communities.