Coniferous-to-broadleaved forest conversion in subtropical coastal sandy lands enhances soil component respiration: coupled driving effects and mechanisms for improved carbon sequestration stability.

Introduction: Coniferous_to_broadleaved forest conversion reshapes soil carbon cycling in coastal sandy ecosystems, yet its regulation on component soil respiration and thermal sensitivity remains poorly quantified. To explore the regulatory effects and underlying mechanisms of such vegetation shift on soil carbon cycling in subtropical coastal sandy lands, we carried out this comparative field study. Methods: We investigated the conversion from Results: Results showed that the conversion significantly increased total soil respiration (by 25.52%), root respiration (by 62.74%), and heterotrophic respiration (by 9.01%). This promotion was driven by the coupled effects of improved litter quality (low C/N ratio and lignin content), a sharp increase in fine root biomass (by 272.5%), and enhanced microbial activity. It also notably reduced the temperature sensitivity ( Discussion: This conversion achieves a virtuous cycle of "high carbon turnover and high carbon sequestration", clarifying the above_belowground coupling mechanism of soil carbon dynamics. Our findings thereby provide important scientific support for the optimization of coastal protection forests and the enhancement of carbon sequestration capacity in fragile coastal ecosystems.