*, **, and *** indicate significant differences at P < 0.05, P < 0.01, and P < 0.001 respectively.

ANOVA was used to compere the effects of different N application on soil microbial biomass under different ecosystems and multiple comparisons were performed using the LSD method. The small letters in rows are the comparison of the effects of different N types on soil microbial biomass for each ecotype; the capital letters in columns are the comparison of soil microbial biomass in different ecotypes for each N type.

The same letter means no statistically significant difference among the treatments under the level of P < 0.05.

The details were shown in Supplemental Information 7 .