While soil ecosystems undergo important modi cations due to global change, the e ect of soil properties on plant distributions is still poorly understood. Plant growth is not only controlled by soil physico-chemistry but also by microbial activities through the decomposition of organic matter and the recycling of nutrients essential for plants. A growing body of evidence also suggests that plant functional traits modulate spe- cies’ response to environmental gradients. However, no study has yet contrasted the importance of soil physico-chemistry, microbial activities and climate on plant species distributions, while accounting for how plant functional traits can in uence species- speci c responses.

Using hierarchical e ects in a multi-species distribution model, we investigate how
four functional traits related to resource acquisition (plant height, leaf carbon to nitro-
gen ratio, leaf dry matter content and speci c leaf area) modulate the response of
44 plant species to climatic variables, soil physico-chemical properties and microbial 100 decomposition activity (i.e. exoenzymatic activities) in the French Alps.

Our hierarchical trait-based model allowed to predict well 41 species according to the TSS statistic. In addition to climate, the combination of soil C/N, as a measure of organic matter quality, and exoenzymatic activity, as a measure of microbial decom- position activity, strongly improved predictions of plant distributions. Plant traits played an important role. In particular, species with conservative traits performed bet- ter under limiting nutrient conditions but were outcompeted by exploitative plants in more favorable environments.

We demonstrate tight associations between microbial decomposition activity, plant functional traits associated to di erent resource acquisition strategies and plant dis- tributions. is highlights the importance of plant–soil linkages for mountain plant distributions. ese results are crucial for biodiversity modelling in a world where both climatic and soil systems are undergoing profound and rapid transformations.