Is decomposition of woodland leaf litter influenced by its species richness?

Abstract

Decomposition of leaf litter was surveyed during the first nine months of decomposition in the field. At three woodland sites that differ with respect to leaf litter species richness, as well as to microbial activity and the abundance of terrestrial isopods, being the most numerous representatives of the saprophagous macrofauna at these sites, changes in the chemical composition of the mixed leaf litter were monitored on a three-monthly basis. Six out of seven leaf litter compounds exhibited changes in their contents that were positively correlated with high microbial activity and/or high isopod abundance during decomposition. Further, site characteristics other than soil pH, water holding capacity (WHC) or percent sand, significantly explained the variance in decomposition of five different chemical compounds, as well as the overall mass loss of leaf litter. These site characteristics include the site-specific species richness of the litter layer. At the site with low microbial activity and low isopod numbers but a leaf litter mixture of nine species, decomposition did not proceed more slowly than at that site with high microbial activity and high isopod abundance but leaf litter made up by only five species. From these results, I hypothesize that a diverse vegetation, resulting in leaf litter of high species richness, promotes decomposition processes, and thus nutrient recycling.