Additive effects of experimental climate change and land use on faunal contribution to litter decomposition

Litter decomposition is a key process determining the cycling of nutrients in ecosystems. Soil fauna plays an essential role in this process, e.g., by fragmenting and burrowing surface litter material, and thereby enhancing microbial decomposition. However, soil fauna-mediated decomposition might be influenced by interacting factors of environmental changes. Here we used a large-scale global change field experiment to test potential interacting effects between land-use type (croplands and grasslands differing in management intensity) and projected climate change on litter decomposition rates over a period of two years. For that, climate and land-use treatments were orthogonally crossed: (1) two climate scenarios: ambient vs. future; and (2) five land-use regimes: conventional fanning, organic farming, intensively used meadow, extensively used meadow, and extensively used pasture. Litterbags with two mesh sizes (5 mm and 0.02 mm) were used to differentiate contributions of microbes and fauna to the mass loss of standardized crop residues. Soil fauna accounted for more than 68% of surface litter mass loss. Future climate treatment decreased decomposition rates as a result of reduced precipitation and elevated temperature during summer months. Litter decomposition and the contribution of soil fauna to it were significantly higher in croplands than in grasslands, but did not differ due to management intensity within these land-use types. In grasslands, faunal contribution to decomposition decreased under future climate. There were no interacting effects between climate change and land use on decomposition rates. These findings indicate that predicted changes in precipitation patterns and temperature will consistently decelerate litter decomposition across land-used types via both microbial and faunal effects.