highly significantp < 0.001
Similar patterns for community differences across the sites were observed for nirK , nirS , nosZ , nifH and archaeal amoA functional genes, as indicated by the Procrustes analysis, with highly significant goodness-of-fit measures (M 2 ranging from 0.31 to 0.55; p < 0.001 in all cases, except between nirS and archaeal amoA genes (p < 0.01)) (Supplementary Table 4 ).