Based on the data collected by Fuge`re et al. (2012) and some others, it would arguably be premature to conclude that stress plays either a minor or an important role in determining outcomes of biodiversity change on ecosystem processes. Given the multitude of possible interactions, especially when food-web and microbial interactions are added to the basic template of plant–plant interactions, it is likely that a complex interplay between species interactions, stress and resource availability changes the relative importance of each factor across environmental gradients (Ellison 1987; Callaway 1997). The type of stress, the way it is assessed, and variation in responses to a particular stress type and level across species are likely to complicate patterns further. As a result, the overall net effect of species interactions on ecosystem processes may be negative, neutral or positive, and different outcomes may be expected for different processes in a given system.