Leaf litter quality coupled to Salix variety drives litter decomposition more than stand diversity or climate

Aims Decomposition of leaf litter is influenced by litter quality as determined by plant genotype and environment, as well as climate and soil properties. We studied these drivers of decomposition in communities ofSalixvarieties, hypothesizing that decomposition rates would increase under warmer climate, in more diverse communities, and with increasing litter quality of the individual varieties. Methods Litter from fourSalixvarieties was incubated in three field trials across a latitudinal gradient from Central to Northern Europe. Litter and stand properties were measured and used as predictors of decomposition. Results No significant site differences in remaining mass or nitrogen were found. Instead, effects of initial leaf litter quality on decomposition were stronger than climatic effects. Litter quality of individual varieties strongly affected decomposition, while increasing litter diversity did not. Conclusions Decomposition was controlled by variety identity depending on site, indicating that local soil conditions affect litter quality (and thus decomposition) more than macroclimate. In mixed communities, varieties producing fast-decomposing litter enhanced the litter decomposition of other components producing slow-decomposing litter, and vice versa. This implies that site conditions partly determine which varieties affect community-level decomposition and nutrient release.