Microbial biomass C:N:P as a better indicator than soil and ecoenzymatic C:N:P for microbial nutrient limitation and C dynamics in Zoige Plateau peatland soils

Abstract

Peatland soils are important carbon (C) sinks, and microbial nutrient limitation controls C storage or release through microbial metabolism under the available nitrogen (N) and phosphorus (P). Currently, soil, ecoenzymatic, and microbial biomass C:N:P are widely used stoichiometric indicators to reveal nutrient status. However, it is unclear whether these indicators are effective in revealing microbial nutrient limitation consistently and which one of them can better indicate nutrient limitation and C dynamics. Therefore, this study compared nutrient status using these C:N:P ratios in different types and depths of Zoige peatland soils and evaluated the relationships between various C:N:P ratios and soil organic C (SOC) contents. Results showed that soil and ecoenzymatic C:N:P ratios indicated P limitation, while microbial biomass C:N:P ratios suggested N limitation. The homeostasis index suggested that microbes were in strict homeostasis, implying that microbial biomass C:N:P stoichiometry was a better indicator for microbial nutrient limitation and status. In addition, it was found that the direct effect of microbial C:N:P ratio on SOC (44%) was higher than soil and ecoenzymatic C:N:P ratios (32%); N-acquiring enzymes and different N species were more closely related to SOC than the counterparts of P. Therefore, microbial biomass C:N:P ratio might be a better indicator to reveal C dynamics in the peatland ecosystem. With the microbial biomass C:N:P ratios, the nutrient status of the microbiomes and the dynamics of SOC under nutrient intervention (e.g., N deposition) can be delineated.