Disentangling the processes driving plant assemblages in mountain grasslands across spatial scales and environmental gradients

Habitat filtering and limiting similarity are well‐documented ecological assembly processes that hierarchically filter species across spatial scales, from a regional pool to local assemblages. However, information on the effects of fine‐scale spatial partitioning of species, working as an additional mechanism of coexistence, on community patterns is much scarcer. In this study, we quantified the importance of fine‐scale spatial partitioning, relative to habitat filtering and limiting similarity in structuring grassland communities in the western Swiss Alps. To do so, 298 vegetation plots (2 m × 2 m) each with five nested subplots (20 cm × 20 cm) were used for trait‐based assembly tests (i.e., comparisons with several alternative null expectations), examining the observed plot and subplot level α‐diversity (indicating habitat filtering and limiting similarity) and the among‐subplot β‐diversity of traits (indicating fine‐scale spatial partitioning). We further assessed variations in the ...