Tree Species Diversity Regulates the Contribution of Microbial Necromass to Soil Organic Carbon Accumulation in a Subtropical Forest

Abstract

Higher plant diversity has a consistent positive effect on long-term soil organic carbon (SOC) storage in the forest ecosystem. Shifts in plant-derived organic matter into SOC are dominated by soil microorganisms, yet the interactions among tree species diversity (TSD), soil properties, microbial physiology parameters, and microbial necromass carbon (MNC) accumulation in forest SOC storage remain poorly understood. In the present study, we examine changes in soil biotic and abiotic variables induced by increased TSD and the effects of these variables on the MNC and SOC contents in a typical subtropical forest in southwest China. Our results demonstrate that TSD exerts positive effects on microbial growth, biomass, and necromass. We determine that the microbial biomass C and the MNC contents are strongly and positively related to SOC storage. TSD is shown to significantly enhance the soil substrate and the soil water content, which could enable faster rates of microbial growth and turnover owing to greater plant-derived organic matter inputs for MNC formation. In addition, TSD positively affects mineral protection, which directly promotes MNC accumulation. Collectively, the TSD effect on MNC and its contribution to SOC storage is determined by variations in soil properties and microbial factors. Our findings exhibit microbe-dependent linkage between TSD and the forest C cycle process and emphasize the importance of microbial necromass in the Earth’s climate system for accurate prediction of soil C dynamics under global climate change.

Keywords: tree species diversity, microbial necromass C, soil organic carbon, microbial physiological parameters, mineral protection, subtropical forest