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).