Controls on extracellular enzyme activity throughout the top meter of soil
Consistently, MB, SOC, and fungi:bacteria were better predictors of EE activities per mass of soil than pH or clay concentrations (Table S2). This was generally consistent among surface soil- and subsoil-only datasets except for fungi:bacteria, which was only a strong predictor in the surface soil (Table S3).
Normalized by SOC or MB, soil pH was generally not a significant predictor of the assayed EE activities. The exception was LAP kg-1 SOC, which correlated positively with pH (p = 0.037; all other EEs: p > 0.05; Table S4), a pattern that was consistent among surface soil- and subsoil-only datasets (Table 2). In contrast, when EE activities were normalized per unit MB, clay concentrations and fungi:bacteria were generally correlated positively with EE activities (Table S4). When surface and subsoil EE data were analyzed separately, the effect of clay concentrations and fungi:bacteria on MB-normalized EE activities was more often significant in the subsoil (Table 2).