How invasion by Ailanthus altissima transforms soil and litter communities in a temperate forest ecosystem

The invasive tree Ailanthus altissima (Mill.) Swingle (tree of heaven) is considered as an ecosystem transformer, which alters plant communities in open areas and forests. Nothing is yet known about its potential effects on forest soil biota and ecosystem functioning. We present here the first study assessesing the impact of A. altissima on soil and litter invertebrate communities in a temperate forest. We analyzed the effect of varying A. altissima densities in a forest of north-eastern France on soil microbial activity, diversity of various litter and soil invertebrate groups (Arthropoda, Lumbricidae, Gastropoda), diversity of functional groups (predatory, detritivorous, coprophagous, phytophagous), and trophic structure. Our study shows that increasing density of A. altissima is associated to lower soil microbial activity, decreasing abundance of litter detritivores (Acari and Collembola) and aboveground predatory Coleoptera, and decreasing species richness of terrestrial Gastropoda. In contrast, increased A. altissima density corresponded with greater abundances of litter Lumbricidae and aboveground coprophagous Coleoptera. We found an overall impact of A. altissima invasion on the soil food web structure that could accelerate the mineralization of organic matter and potentially favor nitrophilous plant species in understory plant communities.