Résumé
1. At broad spatial scales, the factors regulating litter decomposition
remain ambiguous, with the understanding of these factors largely based on
studies investigating site-specific single litter species, whereas studies
using multi litter species mixtures across sites are rare. 2. We exposed
in microcosms containing single species and all possible mixtures of four
leaf litter species differing widely in initial chemical and physical
characteristics from a temperate forest to the climatic conditions of four
different forests across the northern hemisphere for one year. 3. Calcium,
magnesium and condensed tannins predicted litter mass loss of single
litter species and mixtures across forest types and biomes, regardless of
species richness and microarthropod presence. However, relative mixture
effects differed among forest types and varied with the access to the
litter by microarthropods. Access to the microcosms by microarthropods
modified the decomposition of individual litter species within mixtures,
which differed among forest types independent of litter species richness
and composition of litter mixtures. However, soil microarthropods
generally only little affected litter decomposition. 4. Synthesis. We
conclude that litter identity is the dominant driver of decomposition
across different forest types and the non-additive litter mixture effects
vary among biomes despite identical leaf litter chemistry. These results
suggest that across large spatial scales the environmental context of
decomposing litter mixtures, including microarthropod communities,
determine the decomposition of litter mixtures besides strong litter trait
based effects.