Differential responses of soil hydrolytic and oxidative enzyme activities to the natural forest conversion.
soil microbial extracellular hydrolytic enzymatic activities (Hy-EEAs), soil oxidative enzymatic activities (Ox-EEAs), soil carbon (C), soil nitrogen (N), soil phosphorus (P)
natural forest conversion (NFC)
Changes in soil Hy- and Ox-EEAs, changes in soil organic C, available P, microbial biomass C and N
depletion of soil organic carbon, stimulated soil microbial secretion of Hy- and Ox-EEAs, soil total N scarcity, provoke soil microbial Hy-EEAs, soil total P dearth, quickened the soil Ox-EEAs, plenitude of soil available P, suppressed soil Hy- and Ox-EEAs
Abstract
Effects of natural forest conversion (NFC) on soil nutrient turnover are substantially mediated by soil microbial extracellular hydrolytic enzymatic activities (Hy-EEAs) and oxidative enzymatic activities (Ox-EEAs). Yet it remains largely unknown the indicative links between soil Hy- and Ox-EEAs and soil carbon (C), nitrogen (N) and phosphorus (P) supplies based on economic theories of microbial metabolism under NFC. Here we used a meta-analysis approach to synthesize the responses of the soil C-, N-, P-degrading Hy-EEAs and Ox-EEAs, soil microbial biomass, soil organic C, total N, P and available P parameters to natural forest conversion from 51 peer-reviewed studies. Our results showed that NFC notably decreased soil Hy-EEAs but statistically insignificant reduction of soil Ox-EEAs. The changes of soil Hy- and Ox-EEAs were significantly and positively associated with soil organic C, available P as well as microbial biomass C and N but significantly and negatively correlated with soil pH, whereas the changes of soil C/N impacted on soil Ox-EEAs remarkably but not for soil Hy-EEAs. The depletion of soil organic carbon stimulated soil microbial secretion of Hy- and Ox-EEAs. The soil total N scarcity only provoked soil microbial Hy-EEAs rather than Ox-EEAs. The soil total P dearth quickened the soil Ox-EEAs, however, the plenitude of soil available P suppressed soil Hy- and Ox-EEAs. Moreover, the eco-enzymatic stoichiometry of soil Hy-EEAs indicated that soil N and P nutrient limitation after NFC restricted soil microbial N- and P-acquiring enzymes secretion, which ultimately reduced resources availability for C acquisition. Altogether, the distinct responses of soil Hy- and Ox-EEAs depended on substrate availability peculiarly for soil N and P gains of microorganisms for further enzymatic ability on soil C decomposition and highlighted the abundant or absent supply of soil N and P for positive or negative enzymatic activities on metabolic requirement of soil edaphons.