Table 2. The correlation between environmental attributes and microbial community functional structures by Mantel tests.

Environmental attributes	r	P
pH	0.08	0.215
Organic matter	−0.11	0.788
Moisture content	0.11	0.144
Relative humidity	0.27	0.007a
Total N	0.03	0.365
Available N	0.39	0.002
NO3−	0.00	0.455
NH4+	0.27	0.013
Total P	0.24	0.038
Available P	0.34	0.003
Total K	0.20	0.050
Available K	0.17	0.108
Precipitation	0.21	0.029
Annual temperature	0.26	0.008
Grain	0.25	0.043
Maize biomass	0.37	0.009
CO2 efflux	0.58	0.001
Nitrification potential	0.35	0.002

Abbreviations: K, potassium; N, nitrogen; P, phosphorus.

^aLetters in bold are statistically significant (P<0.050).