Correlations between unweighted UniFrac distances and environmental parameters (Spearman rank correlations estimated using Mantel tests)a

Phylum (no. of soils)Correlation
Soil pHSoil moisture deficitC/N ratio% OCMAT (°C)Potential C mineralization rate (μg C-CO2 g soil−1 day−1)% Silt plus clay
Full community (88)0.790.500.
Acidobacteria (69)0.720.300.
Actinobacteria (66)0.630.400.
Alphaproteobacteria (69)0.700.370.
Beta/Gammaproteobacteria (69)0.530.340.
Bacteroidetes (57)0.370.450.
  • a Significant correlations are indicated in bold (P < 0.01). Other soil and site characteristics that were tested but were not included in this table because there were no significant correlations (P > 0.15 in all cases) include mean annual precipitation, extractable NH4+ and NO3 levels, total microbial biomass, potential evapotranspiration, and latitude. Multivariate correlations did not increase the correlation coefficients.