How litter decomposition is (or isn’t) affected by species diversity

Background/Question/Methods

The rapid changes in biodiversity observed worldwide have the potential to greatly affect ecosystem processes such as primary production and decomposition. Decomposition plays a crucial role in both terrestrial and many aquatic ecosystems. However, assessments of diversity effects on decomposition have lagged behind investigations into effects on primary production. Here I use a recently accumulated body of experimental evidence to evaluate how common diversity effects are on plant litter decomposition and which mechanisms might be underlying them.

Results/Conclusions

Insightful lab and field experiments have provided strong evidence that the species richness of leaf litter, microbial decomposers and litter consuming detritivores can be important in determining decomposition rates. However, these effects are not universal, suggesting that context dependency is important. Elucidating the mechanisms behind diversity effects provides insights to understand context dependency. Two approaches have been taken towards this end: statistical analyses and experiments designed to test for specific mechanisms. The latter include selective foraging of detritivores, physical or microbially mediated transfer of nutrients and other cell constituents, complementary enzymatic tissue degradation, and interactive influences on habitat conditions. The rare experiments conducted to date to test for such mechanisms have in no case demonstrated a clear link between species richness and decomposition rate. Mechanistic understanding and generalization of diversity effects on decomposition thus remain a challenge.