Decomposition of Leaf Litter in a U.S. Saltmarsh is Driven by Dominant Species, Not Species Complementarity

Abstract

To add to our understanding of species richness-effects on ecosystem processes, we studied the importance of species complementarity in driving decomposition in a saltmarsh in Georgia, USA. We studied pair-wise interactions of both detritivores and plant litter species and how they affect decomposition rates in an experiment located on the mid-marsh platform. Needle rush, Juncus roemerianus, had 2-3 times higher decomposition rates than cordgrass, Spartina alterniflora, or live oak, Quercus virginiana. Mixing litter types did not promote decomposition rates. Cordgrass decomposition was 1.5-times higher when periwinkles, Littoraria irrorata, were present than in detritivore-free controls. In contrast, neither coffee-bean snails, Melampus bidentatus, nor wharf crabs, Armases cinereum, increased cordgrass decomposition rates. Mixing detritivore species did not increase cordgrass mass loss beyond expected rates from an additive model. We conclude that in this system, species do not act complementarily with each other, but that decomposition rates are controlled by the dominant species of angiosperms and invertebrate detritivores.