Home-Field Advantage : a matter of interaction between litter biochemistry and decomposer biota

Home-Field Advantage (HFA) defines the way with which a plant litter may decompose faster in the habitat from which it derives (i.e. home) than beneath a different plant community (i.e. away from home). Recent studies, using plurispecific litter and involving several soil biota groups, failed to demonstrate a clear positive HFA effect. The interactions between different soil biota groups and different litter types may cause additive effect on decomposition process. Concomitantly, new hypothesis was raised which expects a continuum from positive to negative interactions between transplanted litter and host litter as both litters become increasingly dissimilar in quality, which has been called Substrate quality Matrix quality Interaction (SMI). Against this background, we aimed at testing the influence of both litter quality and soil organisms in determining the HFA and the SMI hypothesis. We used reciprocal plurispecific transplanting litter along a gradient of litter quality with three successional stages: early (S1), medium (S2) and late successional stage (S3), coupled with litterbags of different mesh size to select different decomposers communities. Furthermore, we analyzed litter quality in order to test the SMI hypothesis. Overall, we did not observe a general HFA or SMI effect. In micromesh litterbags, only S1 litter showed an HFA effect (+7%) while in mesomesh litterbags, only S2 litter presented an HFA effect (+8%). The contribution of each litter quality fraction to the HFA index allowed us to show that only highly labile fractions (i.e., solubles and hemicellulose) presented a positive HFA index, independently of the mesh size. Indeed, our findings corroborated the SMI hypothesis but for labile fraction only. Finally, our results highlighted a strong inertia between different soil decomposer groups for the attack of the most recalcitrant biochemical fraction (i.e. lignin) only in late stage, independently of the litter origin