<b>Tree species diversity reduces </b><b>priming effects</b><b> in a subtropical forest</b>

Soil organic carbon (SOC) is an important terrestrial C pool and increasing it contributes to global climate change mitigation. While tree planting can increase soil C content through new plant C inputs to soil, it may also enhance the mineralization of native SOC, and counterbalance net soil C sequestration. It has been often shown that high tree species diversity can result in increased plant productivity and, subsequently high C inputs to soil. However, whether this translates into net SOC accumulation or increased decomposition (‘priming’) of existing SOC remains unclear. Here, we determined the influence of tree species diversity on SOC priming in a subtropical forest by conducting ¹³C–glucose labeling experiments. Priming of SOC decreased as tree species diversity increased, indicating that soil microbial communities in species–rich forest preferentially mineralized added glucose rather than SOC. Priming was driven by microbial community assemblages with low growth yields and high C degradation-related gene abundance, which were more dominant in species-poor forest. We further reveal an interaction with soil mineralogy, as lower priming in species-rich forest was accompanied by greater relative abundance of mineral–organic associations, offering protection of SOC from mineralization. Our results demonstrate that plant diversity can result in linked feedbacks on soil microbial communities and soil mineralogy, thereby modulating priming and ultimately determining soil C sequestration.