Root-centric β diversity reveals functional homogeneity while phylogenetic heterogeneity in a subtropical forest

Root-centric studies have revealed fast taxonomic turnover across root neighborhoods, but how such turnover is accompanied by changes in species functions and phylogeny (i.e. β diversity), which can reflect the degree of community-wide biotic homogenization, remains largely unknown, hindering better inference of below-ground assembly rules, community structuring, and ecosystem processes. We collected 2480 root segments from 625 0–30 cm soil profiles in a subtropical forest in China. Root segments were identified into 143 species with DNA-barcoding with six root morphological and architectural traits measured per species. By using the mean pairwise (Dpw) and mean nearest neighbor distance (Dnn) to quantify species ecological differences, we tested the non-random functional and phylogenetic turnover of root neighborhoods that would lend more support to deterministic over stochastic community assembly processes, examined the distance-decay pattern of β diversity, and finally partitioned β ...