Decoding soil carbon and nitrogen dynamics: The integrated role of biotic and abiotic drivers in subtropical forests

Abstract

Accurate estimation of carbon (Scs) and nitrogen (Sns) stocks in forest soils is crucial. In subtropical forests, this storage is influenced by the interplay of various biotic and abiotic factors, including biological attributes such as plant diversity, litter characteristics, and microbial biomass, as well as abiotic attributes like climate, topography, and soil characteristics. However, the relative importance of these interplaying factors in influencing Scs and Sns in subtropical forests remains inadequately understood. In this study, we quantified the Scs and Sns across different soil layers in typical subtropical forests (coniferous, mixed coniferous-broadleaf, and broadleaf forests), and used partial least squares path modeling to determine the relative importance of biotic and abiotic factors on Scs and Sns. Results showed that Scs and Sns declined as soil depth increased, with no significant differences observed among the forest types. However, the driving factors varied significantly across forest types, with soil properties exerting the strongest impact on carbon and nitrogen sequestration. We observed a pronounced synergistic relationship between Scs and Sns. Among the biotic factors, plant diversity and litter characteristics indirectly modulated Scs and Sns by regulating soil water content (SWC) and pH levels. In terms of abiotic factors, elevated altitude and lower temperatures limited plant growth, slowed litter decomposition, and enhanced carbon and nitrogen accumulation. In contrast, adequate SWC and nutrient availability favored the accumulation of organic matter, while soil acidification could lead to carbon and nitrogen loss. In conclusion, forest management strategies that prioritize the optimization of SWC and nutrient conditions are instrumental in fostering carbon and nitrogen sequestration, thus contributing to climate change mitigation.