A facilitation between large herbivores and ants accelerates litter decomposition by modifying soil micro-environmental conditions

1. Large herbivores and insects commonly coexist and play important functional roles in grassland ecosystems. The interactive effects of these two animal groups in shaping ecosystem processes and functioning are poorly understood. In a semi-arid grassland of northeastern China, we previously found a reciprocal facilitation between large herbivores (cattle; Bos tarurs) and ants: cattle grazing led to a two-fold increase in ant mound abundance compared with ungrazed sites, while the presence of ant mounds, in turn, increased the foraging of cattle during the peak of the growing season. 2. Here, by using a large-scale, 4-year (2010-2013) manipulative experiment, we further investigated how such a facilitation between large herbivores and ants can affect a key ecosystem process, litter decomposition. Using a set of small-scale reciprocal translocation litterbag experiments, we separated the effects of litter quality and soil micro-environmental factors altered by cattle and ants on litte...