丛枝菌根和外生菌根树种对亚热带常绿阔叶林土壤有机碳的影响及其调控机制

准确评估和预测森林土壤碳动态，对于评价森林碳汇功能、减缓气候变化意义重大。尽管树木菌根类型在理论上被认为能有效地表征森林土壤碳循环，但在亚热带地区，不同菌根类型树种占优势的森林土壤有机碳库及其分布格局、主要形成途径和稳定机制是否一致，目前仍然是不清楚的。本项目拟以江西省九连山常绿阔叶林作为研究对象，分别选取丛枝菌根和外生菌根树种占优势的森林（优势度>0.80），比较不同菌根类型森林土壤有机碳库和垂直分布格局的差异，采用13C稳定同位素技术解析土壤有机碳组分的来源，揭示不同菌根类型森林土壤有机碳库形成的主要途径，并运用氨基糖生物标志物技术研究微生物残体对矿物结合有机碳的贡献，明确不同菌根类型森林土壤有机碳的主要稳定机理。基于以上研究内容，明确树木菌根类型对亚热带森林土壤有机碳分布格局、形成过程和稳定机制的影响及其驱动因素，不仅有助于理解森林土壤有机碳动态，也可为区域碳汇林业建设提供理论指导。

Assessing and predicting forest soil carbon (C) dynamics are of great importance to evaluate forest C sink and mitigate climate change. According to the mycorrhizal-associated nutrient economy, tree mycorrhizal type is commonly thought to an integrated index that can effectively indicate soil C cycle in forests. However, whether the mycorrhizal association of trees can reflect soil organic C pool and its distribution pattern is still elusive in subtropical regions due to the lack of empirical studies. Moreover, it remains unclear whether the primary formation pathways and stabilization mechanisms of soil organic C are consistent in forests with contrasting tree mycorrhizal associations. In this proposed project, we will establish 12 pairs of arbuscular mycorrhizal and ectomycorrhizal tree-dominant stands (dominance >0.80, and 20 m×20 m in size) in the typical subtropical evergreen broadleaf forests in the Jiulianshan Mountain, Jiangxi Province. First, we will compare the differences in soil organic C pool and its vertical distribution pattern in arbuscular mycorrhizal and ectomycorrhizal tree-dominated stands. Second, using the 13C stable isotope technique, we will uncover the effect of tree mycorrhizal types on the primary formation pathways of soil organic C pool by tracing the sources of soil organic C and fractions in these forests. Third, using the microbial residue biomarker (amino sugars), we will assess soil organic C stabilization mechanisms by measuring the contribution of soil microbial necromass C to mineral-associated organic C in these ecosystems. Based on these studies, we will reveal the effect of tree mycorrhizal types on the distribution patterns, formation processes, and stabilization mechanisms of soil organic C pool and their driving factors in subtropical evergreen broadleaf forests. The results from this project will not only help to understand the dynamics of soil organic C pool in forest ecosystems, but also provide the reference for tree species selection during the construction of C sequestration forestry at the regional scale.