基于超声能量法研究凋落物分解与土壤团聚体作用机制

Soil aggregates control the movement and storage of water, air, heat and nutrients in soils. The effect mechanic of litter decomposition on soil aggregate is an important theoretical basis for restoration and reconstruction of soil ecosystem under vegetation restoration. To uncover the effect mechanic, this study will incubate Liaodong oak soil under laboratory / field in-situ condition with litter amendment. Considering the effect of soil initial organic carbon in forming soil aggregate, both surface soils rich in carbon and deep lean soils in low carbon will be investigated comparably. During incubation, the changed of soil aggregates, including their relative strength (RSA), particle distribution, and mean weight diameter (MWD), will be assessed by ultrasonic dispersion and wet-sieving. These will illustrate the mechanical of forming aggregate together with the change of soil microbe (biomass, enzyme, diversity, etc.) and function group monitored. Moreover, a hypothesis of "adaptive formation of aggregates" will be proposed with evidences in coexistence of multi-level agglomeration and reverse-agglomeration theory. The study will promote to exploring aggregate formation theory, and theoretically support the protection, restoration and reconstruction of soil ecosystem under vegetation restoration.

土壤团聚体控制着土壤水、肥、气、热的保持和运移。凋落物分解与团聚体作用机制是植被恢复下土壤生态系统修复与重建的重要理论基础。鉴于该机制不明确及现有团聚体评估技术的局限性，本项目拟采选用辽东栎凋落物作为外源碳，通过控制其输入（质和量），在室内和野外原位条件下分别培育有机碳含量不同的表层土和深层贫瘠土，采用超声能量法建立团聚体相对稳定指数（RSA），并结合粒径分布和平均重量直径（MWD）量化团聚体稳定性变化特征，进而综合有机碳官能团和微生物（生物量、酶、多样性等）变化指标，从物理、化学和微生物过程阐述凋落物分解与土壤团聚体作用机制；此外，获取多级团聚理论和反向团聚学说并存证据，提出团聚体“环境自适应形成”假说，从而为系统研究土壤团聚体形成理论提供参照和科学数据，为研究植被恢复下土壤生态系统的保护、恢复及重建工作提供科学依据。

窥探土壤团聚体形成机制的关键是对团聚体稳定性的定量评价。对比分析了Yoder改进法、Le Bissonnais法和超声能量法在评价黄土高原不同植被覆盖下土壤团聚体稳定性的差异，研究了黄土高原人工林的适宜性与可持续性；在此基础上，基于超声能量法提出了团聚体相对稳定性RSA指数和表征土壤抗破坏能力的表观能量EA指数，两者互为倒数关系。对比分析透射、衰减全反射和漫反射三种傅里叶红外光谱方法的理论与技术特点后，阐明了漫反射红外光谱方法在土壤有机碳官能团定量分析的技术可行性；通过室内土壤培育实验研究植被残体分解中土壤团聚体稳定性和土壤典型基团/官能团的变化特征，阐明了影响团聚体稳定性的主要基团/官能团。给合三年的子午岭原位土壤培育实验研究了辽东栎凋落物分解中土壤团聚体的形成过程，阐述了培育期间土壤表观能量指数的变化特征，阐明了影响团聚体稳定性的主要化学性质和微生物群落组成。本研究可为土壤团聚体形成机制的探索研究提供方法参照和科学数据，为植被恢复下土壤生态系统的保护与重建提供理论依据。