Humans are profoundly affecting global biodiversity, which potentially has consequences for biogeochemical processes and the benefits afforded to humans by ecosystems (Naeem, Duffy & Zavaleta 2012). Concern regarding these consequences has spurred intense research over the past two decades to assess the impact of changing biodiversity on the rates at which resources are captured and processed by biological communities (Cardinale et al. 2012). Much of this research has focused on plant communities, where long-term studies (Reich et al. 2012) and meta-analyses (Hooper et al. 2012) consistently show that increasing species richness enhances plant productivity. The prevalence of similar effects on plant litter decomposition is, however, less clear (Gessner et al. 2010; Hooper et al. 2012). This suggests that environmental context plays an important role in determining the influence of biodiversity loss on decomposition (e.g. McKie et al. 2009; Gessner et al. 2010; Kominoski et al. 2010).