Tree canopy shapes and buffers detritivore invertebrate responses to soil temperature variability

Abstract Soil fauna are fundamental components of terrestrial ecosystems, supporting organic matter decomposition, nutrient cycling, and soil formation. Among soil invertebrates, earthworms (Annelida) and springtails (Collembola) play key and complementary functional roles, yet their responses to climate are strongly mediated by soil conditions and vegetation structure. Due to their limited dispersal capacity and reliance on soil temperature and moisture, these taxa are expected to be highly sensitive to ongoing climatic change. Using a large-scale dataset spanning the Northern Hemisphere, we investigated how soil properties and climate-related factors interact with the vegetation canopy to shape patterns of Annelida and Collembola species richness. We combined biodiversity data with gridded soil temperature, precipitation, and snow-related variables, and analysed richness using negative binomial mixed models, explicitly testing interactions between environmental drivers and tree canopy, while accounting for spatial clustering. Soil pH emerged as an important driver of richness in both taxa, but its effect was strongly mediated by canopy, being most pronounced in closed-canopy habitats and attenuated or absent in more exposed systems. Climate-related variables showed marked, canopy-dependent effects. For Annelida, thermal conditions and water availability exerted contrasting influences across habitats, with open and non-forested sites being particularly sensitive to thermal instability and moisture limitation, whereas closed-canopy forests buffered these effects. Collembola displayed a more restricted response pattern, with richness primarily benefiting from stable and buffered microclimates under closed canopies, while exposed habitats showed negative responses to climatic variability. Overall, our results demonstrate that belowground biodiversity is shaped by the interaction between soil properties, climate, and vegetation structure. Vegetation canopy acts as a critical mediator of climatic impacts on soil fauna, highlighting its key role in buffering future climate effects on soil biodiversity by strong interactions between the green food web and the brown food web.