Differential linkages between soil respiration components and microbial community structures under long-term forest conversion

Purpose Soil respiration (Rs) can be significantly impacted by land-use change (LUC). This study aimed to determine the response of Rs components (i.e., heterotrophic respiration (Rh) and autotrophic respiration (Ra)) to long-term forest conversion and explore their associations with soil microbial community (SMC) structures. Materials and methods Three plantations converted from natural forest 36 years ago were investigated: Cryptomeria fortune (CF), Cunninghamia lanceolata (CL), and Metasequoia glyptostroboides (MG), with the control of an adjacent natural forest (NF). In each forest site, Rh and Ra were measured using the root trenching method during the growing season. SMC structures in trenched and rhizosphere soils (0-10 cm depth) were analyzed. Results We observed an evident differentiation between SMC structures in trenched and rhizosphere soils across forest types. SMC structural dynamic in trenched soil was primarily driven by the ratio of dissolved organic carbon (c) to dissolved organic nitrogen (DON) and bulk density, whereas that in rhizosphere soil was primarily driven by DON and pH. During the growing season, both Rh and Ra were greater in MG than in NF, but they showed non-significant differences among NF, CF, and CL. The Rh pattern was primarily modified by the SMC structure (e.g., arbuscular mycorrhizal fungi (AMF)) and soil temperature, whereas the Ra pattern was primarily modified by the SMC structure in rhizosphere soil (e.g., gram-positive bacteria (GP)) in addition to fine root quality and soil temperature. Conclusions Rh and Ra patterns were jointly modified by SMC structure and microenvironment over long-term forest conversion, emphasizing the underlying roles of plant community attributes and forest management in soil C emission into the atmosphere.