Determining Changes in Microbial Nutrient Limitations in Bamboo Soils under Different Management Practices Via Enzyme Stoichiometry

Moso bamboo (Phyllostachys edulis) is a plant species recognized for its extremely high carbon sequestration potential, and, along with soil microbes, play a key role in the carbon (C) cycle. Nevertheless, the metabolic constraints of soil microorganisms in the ecosystem have rarely been studied. We investigated changes in soil extracellular enzyme activities and microbial nutrients limitation in three different managed Moso bamboo plantations. The results showed that compared to nonmanagement (M0), extensive (M1) and intensive (M2) management significantly (p <= 0.05) decreased the activities of C- (13-1,4-glucosidase, BG) and N-acquiring (13-1,4-N-acetylglucosaminidase (NAG) and L-leucine aminopeptidase (LAP)) enzymes and significantly (p <= 0.05) increased the activity of soil P-acquiring enzymes (acid phosphatase, ACP). M1 and M2 exhibited significantly (p <= 0.05) decreased ratios of ln(BG):ln(ACP) and ln(NAG + LAP):ln(ACP) compared to M0. The ln(BG):ln(NAG + LAP) ratio in M2 was significantly (p <= 0.05) lower than in M0 bamboo plantations. M1 and M2 had a lower vector length and higher vector angle than M0, suggesting that management practices can reduce the microbial C and N limitations in bamboo plantations. In contrast, boosted activity of the C-acquiring enzyme, high levels of total organic C concentration, and increased microbial C constraint in M0 and M1 indicated that reducing disturbance benefits soil C stability and renders C hard to use by microorganisms. Random forest analyses indicated that total N and pH were the most important predictors of microbial C and N limitations in bamboo soils, respectively. This study revealed that the intensity of management practices markedly affected the balance between soil microbial nutrient requirements and C sequestration in Moso bamboo plantations.