Does spatial distribution of tree size account for spatial variation in soil respiration in a tropical forest?

Abstract

We explored the relationship between soil processes, estimated through soil respiration (R soil ), and the spatial variation in forest structure, assessed through the distribution of tree size, in order to understand the determinism of spatial variations in R soil in a tropical forest. The influence of tree size was examined using an index (I c ) calculated for each tree as a function of (1) the trunk cross section area and (2) the distance from the measurement point. We investigated the relationships between I c and litterfall, root mass and R soil , respectively. Strong significant relationships were found between I c and both litterfall and root mass. R soil showed a large range of variations over the 1-ha experimental plot, from 1.5 to 12.6 gC m−2 d−1. The best relationship between I c and R soil only explained 17% of the spatial variation in R soil . These results support the assumption that local spatial patterns in litter production and root mass depend on tree distribution in tropical forests. Our study also emphasizes the modest contribution of tree size distribution–which is mainly influenced by the presence of the biggest trees (among the large range size of the inventoried trees greater than 10 cm diameter at 1.30 m above ground level or at 0.5 m above the buttresses)–in explaining spatial variations in R soil .