高寒森林凋落物季节性输入对土壤有机质动态的作用

The return and decomposing process of plant litter have important value to the balance of soil organic matter from decomposition of plant litter and its mineralization to inorganic carbon. Affected by climate and environment factor, the existing theories about the relationship between litter and soil organic matter is not clear. Therefore, to study the correlation between litter and soil organic matter, we here hypothesized that litterfall would accelerate the accumulation of soil organic matter, and is regulated by the seasonal freeze-thaw. Based on the work foundation and research platform of our team, alpine forests in the western Sichuan will be taken as study subject. Combined with plant litter substrate quality and environmental factors, the soil respiration, soil organic matter leaching, soil carbon component pool and soil humus composition during different stages (early winter, early spring and summer) will be measured. We will comprehensively analyze all environmental factors and measuring parameters, and delve into the dynamic relation of litter decay and soil organic matter. This project may be helpful to understand the accumulation process of soil organic matter in alpine forest, provide scientific support to maintain soil fertility and improve forest quality.

凋落物的归还和腐解一方面可以促进土壤有机质的积累，另一方面也可能产生“施肥效应”激发土壤有机质的矿化，且受气候和环境因素的影响使得已有关于凋落物与土壤有机质关系的理论并不清晰。因此，以受季节性冻融作用显著的高寒森林为研究对象，依托团队已有的工作基础和研究平台，提出“凋落物输入促进土壤有机质累积，且受季节性冻融调控”的科学假设，通过野外原位控制实验，针对不同关键时期（秋末，春初和夏季）凋落物产量和质量差异，从凋落物输入、土壤呼吸和土壤有机质的淋溶流失等过程研究高寒森林土壤有机质贮量；分析土壤活性碳库、惰性碳库和缓性碳库等有机质稳定性；揭示土壤腐殖质组分的功能碳结构动态。结合凋落物基质质量和环境因子动态，探讨凋落物归还和腐解过程与土壤有机质动态平衡的维持机制，以期更加清晰地认识高寒森林土壤有机质累积与“自肥”机制提供科学依据。

依托前期工作基础，本项目围绕“高寒森林凋落物季节性输入对土壤有机质动态的作用”这一核心目标，在研究区域内选取了针叶林、针阔混交林和阔叶林等三种不同类型的森林，研究了凋落物季节性输入的特征，及其对土壤有机碳和组分、土壤呼吸、微生物群落和腐殖质含量的影响。结果发现，在三种林型中，凋落物自然输入普遍降低了土壤碳组分和腐殖质含量，但提高了土壤呼吸通量；而凋落物自然输入对土壤微生物影响不显著。同时，培养时间显著影响了三种林型土壤碳组分、呼吸通量和腐殖质含量，同样对微生物的影响相对较小。这些结果深入认识了高寒森林土壤有机质的动态过程，丰富了土壤肥力等物质循环理论，为森林可持续经营和管理提供一定的理论基础。