The covariation between soil microbial communities and multidimensional fine‐root economics space

Fine‐root traits play important roles in various ecosystem processes, including carbon and nitrogen cycling, and thus relate to the structure and function of soil microbial community. The fine‐root economics space (RES) represents plant growth strategies along multidimensional axes showing the ‘conservation’ and ‘collaboration’ gradient. Based on the theory that plant growth strategies associate with life strategies of soil microbial communities, we hypothesized that the biomass, structure and diversity of soil microbial communities would correlate with the multidimensional RES. We measured root exudation and other chemical and morphological fine‐root traits across 15 tree species in a tropical common garden in southwestern China. We used phospholipid fatty acid analysis and high‐throughput amplicon sequencing to estimate the fungal‐to‐bacterial ratio and diversity of bacterial community in the soils to corresponding target trees. The dissimilarity of fine‐root traits explained 28% of the variation in the dissimilarity of soil microbial communities across 15 tree species. The varimax‐rotated dim 1 and dim 2 of a principal component analysis reflected the ‘conservation’ and ‘collaboration’ axes of the multidimensional RES, respectively. The ‘conservation’ axis correlated negatively with the fungal‐to‐bacterial ratio and bacterial Shannon index. The ‘collaboration’ axis showed no correlations with microbial indices. Yet, root diameter ranked as the second trait of relative importance in explaining the differences in microbial communities among tree species. Root exudation rate had similar loadings on the root nitrogen concentration side of the ‘conservation’ axis (loading = 0.32) and the specific root length side of the ‘collaboration’ axis (loading = 0.33). It negatively correlated with bacterial OTU richness and the Chao1 index, while it showed no correlation with microbial biomass. Synthesis . Our study highlights that roots of fast‐growing species associate with bacteria‐dominated soil microbial communities showing fast‐growth strategies. The traits on the ‘collaboration’ axis and root exudation were also coupled with soil microbial communities but their relations within the multifunctional RES were complicated. The coupled multidimensional RES and soil microbial communities improve our understanding of plant and soil integration.