Eco-evolutionary outsiders: establishing in a distantly related neighbourhood delays and reorganizes nutrient recycling

Rapid environmental change forces long-lived plants like trees to
immigrate into zones still occupied by phylogenetically distantly related
species. Does such phylogenetic isolation (PI) change the trees’ ecosystem
functioning such as litter decomposition? We studied oaks (Quercus
petraea) of low and high PI, reciprocally transplanting their litters to
identify effect of aboveground litter quality and belowground decomposer
biota. Across 8 and 14 months we quantified decomposition (mass loss,
C-loss and N-loss), decomposer biota (Acari, Collembola, microbes)
and 13C/12C ratio. Across 14 months, aboveground PI retarded
decomposition (mass and C loss). Across 8 and 14 months, above- and
belowground PI extensively altered relationships between decomposition and
abundances/diversities of different soil biota, reduced microbial activity
and 13C/12C ratios. Overall, coexistence of trees with distant
relatives impedes and severely re-organizes C and N recycling. Such
negative ecosystem feedback might prevent trees from tracking and
conserving abiotic niches under environmental change.