Spatial patterns of two co-occurring savanna and forest tree species in a dense fi re-protected savanna fragment

Abstract

Savanna-forest transition under fi re-exclusion could be explained by diff erential competitive performance of savanna and forest species under shading/fi re-exclusion. Aiming to understand strategies related to either habitat affi nity, we investigated spatial patterns of a savanna and a forest species in a fi re-protected savanna. We predicted that: savanna species would have lower abundance than the forest species due to a restriction in the number of open microsites; segregation of size classes and a trend from clumping to regularity with size for forest species due to absence of microsite limitation and intra-specifc competition; and spatial association and increasing clustering with size for savanna species due to microsite limitation. To test these predictions, we described spatial patterns of plants in two size classes in three plots of 0.5 ha. We analyzed spatial patterns and associations of size classes using SADIE methodology. Diff erent from what we expected, both species were more abundant among the studied plots and exhibited an increasing aggregation from small to large size classes. We also found a positive spatial association between size classes of both. Th ese results suggest that both savanna and forest species produce similar spatial patterns independently of habitat affi nity. We discuss the possible processes responsible for the observed patterns.