In a recent paper, Schindler and Gessner (2009) tested how functional diversity of leaf litter explains litter diversity effects on decomposition. Their study builds on a large body of experimental evidence that decomposi tion rates of litter species mixtures are not simply predicted by the component species decomposing in isolation (Gartner and Cardon 2004, Hattenschwiler and Gasser 2005, Kominoski et al. 2007, Lecerf et al. 2007). Such litter diversity effects are thought to be explained by the presence of heterogeneous litter (in terms of leaf degradability) in mixtures, causing deviation (positive or negative) in decomposition of mixtures as compared to the average single-species decomposition of the component litter species (Gartner and Cardon 2004, Hattenschwiler et al. 2005). Func tional diversity represents a valuable framework for testing this hypothesis. Schindler and Gessner (2009) is the first published paper that addresses how functional litter diversity influences in-stream litter decomposition. Their manipulative experiment, with homogeneous and heterogeneous mixtures of litter enclosed in coarse and fine-mesh bags, tested for decomposition rates of individual litter species from monospecific and mixed species assemblages. Based on species-specific decay rates expected from published and unpublished data, they split up a set of nine litter species spanning a broad range of decay rates into three functional leaf groups (slow-, medium-, or fast-decomposing species). Homo geneous mixtures consisted of three litter species taken from a single functional group, and heterogeneous mixtures consisted of one species from each of three functional groups. The planned comparison of homo geneous versus heterogeneous mixtures was used to test for the effect of functional litter diversity on litter