Figure 7 . Correlation between environmental factors and the top 20 most abundant bacterial communities at the phylum level. The X and Y axes represent horizontal and vertical angular environmental factors (species composition), respectively. HC, humus content; GS, specific gravity of solid particles; AP, available phosphorus; TOC, total organic carbon; SOM, soil organic matter; N, soil total nitrogen; C, soil total carbon; NO3–N, nitrate-nitrogen; EC, soil electric conductivity; TDS, total dissolved solid; AK, available potassium; SMC, soil moisture capacity; AN, available nitrogen; NO2–N, nitrite nitrogen; NH4–N, ammonium nitrogen. The red shades represent positive correlation, and the blue shades represent negative correlation. Darker shades represent stronger correlation. (Depth and slope positon (n = 9), forest type (n = 12); *P< 0.05, **P < 0.01, ***P < 0.001.)