Figure legend
Fig. 1. (a) Trajectories by which phylogenetic isolation (PI) of a focal tree might affect litter decomposition and how to, tentatively, infer them. Trajectory 1 (T1, single arrow line): effects of PI on decomposition mediated via the abundance and diversity of decomposers. Tentatively inferred from the abundance/diversity terms in multiple regression analyses [abundance (or diversity) + PI + abundance/diversity * PI -> Decomposition]. Trajectory 2 (T2, double arrow line): effects of PI on decomposition mediatedvia the efficiency of decomposers. Tentatively inferred from the abundance/diversity * PI interaction terms in multiple regression analyses [abundance (or diversity) + PI + abundance (or diversity) * PI -> Decomposition]. Trajectory 3 (T3, triple arrow line): effects of PI on decomposition mediated via the physical conditions of decomposition. Tentatively inferred from the PI terms in multiple regression analyses [abundance (or diversity) + PI + abundance (or diversity) * PI -> Decomposition]. Positive effects on decomposition that are mediated via the biotic trajectories T1 and T2 may also increase the proportion of13C accumulated through the food chain. (b) Phylogenetically closely (left) and distantly related (right) neighbors may affect decomposition of litter of a focal tree via (i) above-ground processes affecting litter quality via abiotic and biotic mechanisms (microclimate, shared enemies, competition); and (ii) below-ground processes affecting the decomposition of a given litter quality via biotic and abiotic mechanisms (microclimate, decomposer community). (c) Experimental design: Transplantation litter between phylogenetically isolated and non-isolated trees permits to disentangle above-ground from below-ground effects.
Fig. 2. Effects of phylogenetic isolation aboveground and belowground (PIA and PIB) in multiple regression analysis on the mass loss, the C loss and the N loss of the oak litter (left panel); (b) the microbial biomass, the abundances of Acari and Collembola in the oak litter (right panel). Empty circle and dashed line stand for the effects of PIA, solid line and solid point stand for the effects of PIB. * indicates partial residuals. Significant effects (P < 0.05) are shown in regression line. r2 represents the explanatory power of each model.
Fig. 3. Effects of phylogenetic isolation aboveground (PIA) and belowground (PIB) on carbon isotopes (13C/12C) of oak litter after 8 and 14 months according to multiple regression analysis. Empty circle and dashed line stand for the effects of PIA, while solid line and solid point stand for the effects of PIB. * indicates the partial residuals. Significant effects (P < 0.05) was shown in regression line. r2 represents the explanatory power of each model.