FIG 6.

Multiple regression on distance matrices (MRM) was used to estimate the relative proportions of variance explained by environmental factors in the turnover of nirK-type and nirS-type denitrifier communities along the altitudinal gradient (a) and the relative variation in nitrification potential explained by nirK-type and nirS-type denitrifier communities (b) in the low- and high-altitudinal sections, respectively. MAT, mean annual temperature; MAP, mean annual precipitation; PR, plant richness; TC, total carbon; TN, total nitrogen; Cond, conductivity. DBH represents the total diameter at breast height. DB, EB, and DC represent the percent representations of deciduous broadleaf trees, evergreen broadleaf trees, and dark coniferous trees, respectively, in total DBH. **, P < 0.01; ***, P < 0.001.