Fig. 3: Environmental factors and ecological processes shaping microbial community structure.

a Associations of the microbial community structure (determined by Bray-Curtis distance) with environmental factors (determined by Euclidean distance) using the partial Mantel test. Partial Mantel’s r values are indicated by the edge width, while the statistical significance is denoted by the edge color. Pairwise correlations of environmental variables are depicted with a color gradient reflecting Spearman’s correlation coefficient. b The relative contribution of each ecological process driving microbial community assembly within the layer based on null model analysis (n = 231). c The difference in the relative importance of ecological processes among three soil layers (n = 231). Different lowercase letters in box plots indicate significant differences for the ecological processes with soil depth (determined by two-sided Wilcoxon test, P < 0.05). SUR surface layer, SUB subsurface layer, PL permafrost layer, MAT mean annual air temperature, AI aridity index, NDVI Normalized Difference Vegetation Index, SR plant species richness, HF human footprint index, LCP1 labile carbon pool I (mainly polysaccharides), RCP recalcitrant carbon pool. Central line and whiskers in each box represent the median and 1.5 times the interquartile range, respectively. Boxes indicate the interquartile range between 25th and 75th percentile. Single points are outliers. Source data are provided as a Source Data file.