Diversity and ecosystem functioning: Litter decomposition dynamics in the Atlantic Rainforest

The relationship between ecosystem functioning and species diversity is important for conservation and restoration management of endangered ecosystems. Here we experimentally analysed the effects of tree species richness and composition on the fundamental ecosystem process of leaf litter decomposition in the Brazilian Atlantic Rainforest. We measured the decomposition rates of leaf litter of eight broad-leaved, native tree species either individually or in mixtures of two, four, or six species. Additionally, we analysed the effect of macro- and meso-invertebrate exclusion using coarse- and fine-meshed litter bags. Species composition, but not species richness, significantly influenced litter decomposition rates. Invertebrate exclusion also influenced litter decomposition, although this effect varied between species and mixtures. Overall, litter decomposition dynamics was non-additive, i.e. observed decomposition rates of litter mixtures differed from what would be expected from the decomposition rates of their component species. However, there were also differences between mixtures, which could be at least partly attributed to the varying influence of invertebrates. We conclude that the relationship between the decomposition subsystem and species diversity in the Atlantic Rainforest follows the idiosyncratic response hypothesis and not the rivet hypothesis. For conservation or reforestation management, our results emphasise the need to maintain or restore the composition of locally native tree species communities rather than to maintain only a high tree species richness.

Research highlights▶ Leaf litter identity and not leaf litter richness influences litter decomposition. ▶ Mixing leaf litter often leads to non-additivity in litter decomposition. ▶ The litter decomposition process is highly idiosyncratic. ▶ Decomposition idiosyncrasy is driven in large part by invertebrate decomposers ▶ Reforestation Management should focus on tree species identity.