Interactive effects of temperature, phosphorus and forest floor structure on Enchytraeidae communities (Annelida, Clitellata)

Soil fauna plays a key role in shaping the structure of forest floors, and vice versa, the structure of forest floors also exerts a significant influence on shaping soil animal communities. Enchytraeidae (Annelida, Clitellata) are a major component of the soil mesofauna, but their response to variations in the structure of forest floors and environmental gradients remains poorly studied. We investigated the effects of temperature and soil phosphorus on Enchytraeidae communities across forest floor layers using DNA metabarcoding. We identified 51 species across 12 genera. Community composition was significantly affected by temperature, phosphorus and layer, as well as their interactions. Additional environmental drivers were fungal phospholipid fatty acids (PLFAs) and substrate-induced respiration that significantly shaped community composition. Abundance and biomass of Enchytraeidae generally peaked in the Of/Oh layer exceeding 45,000 ind. m -2 and 3 g fresh mass m -2 . Biomass in the Of/Oh and Ah layers was similar and exceeded that in the Ol layer by factors of about four and three, respectively. In contrast to abundance and biomass, species richness peaked in the Ah layer. Community-weighted mean body length also varied in an interactive way with temperature and phosphorus and peaked at sites with high temperature and intermediate phosphorus levels. Our results show that temperature and soil phosphorus interactively drive the abundance, biomass, species richness and community composition of Enchytraeidae, with distinct responses across forest floor layers. Moreover, at high temperature, communities in phosphorus-rich sites had the greatest overlap with the other communities along the phosphorus gradient. The results demonstrate the complex interplay of abiotic factors and habitat structure in shaping Enchytraeidae communities in forest floors, with potential consequences for the ecosystem processes they support. Integrating functional traits of Enchytraeidae into future studies will help to understand how such changes in community composition affect ecosystem functioning.