Functional identity regulates aboveground biomass better than trait diversity along abiotic conditions in global forest metacommunities

Although several studies have identified the effects of functional trait diversity (FTD) and/ or identity, i.e., the community-weighted mean (CWM) of a trait, on aboveground biomass (AGB) along abiotic conditions, these effects on AGB in global forest metacommunities are still largely unexplored. Here, we modelled the effects of abiotic (i.e., climate, soil and plot physical conditions) and biotic [i.e., FTD, CWM of conservative traits (CWMCT), CWM of acquisitive traits (CWMAT), and functional dominance (FunDom; based on CWM of plant maximum height or diameter)] factors on AGB in 76 forest metacommunities (from 24 studies). Using multiple linear regression models and piecewise structural equation modeling (pSEM), we tested the hypothesis that both abiotic and biotic factors regulate AGB, but that the mass ratio mechanism underpins AGB of metacommunities in global forests better than the niche complementarity mechanism. We found that abiotic and biotic factors contributed 45.39% and 54.0...