土壤固碳效率差异机制分析－以红壤为例

Soil carbon sequestration is crucial to improving soil fertility and addressing global warming. Application of organic amendments, including straw, green manure, manure, and composts, is the most effective way to enhance carbon storage of agricultural soils. Previous studies indicated that carbon sequestration efficiencies of different organic amendments are quite different and contradictory results were even reported. Soil carbon sequestration efficiencies are also different when organic amendments were applied at different rates. These phenomena could not be explained by traditional theories of soil carbon sequestration. Based on our preliminary investigation on soil microstructure and binding agents at aggregate scale, we proposed the assumption: Organic amendments with different properties effects soil aggregation progress differently and formed different microhabitat, which in turn mediate microbial activities and physically protect soil carbon; the sequestered organic carbon will further benefit soil aggregation and finally formed a positive feedback among soil organic matter – aggregate microstructure – soil binding agent. To verify this assumption and quantify their relationships, we will use the synchrotron-based micro-CT and other cutting-edge techniques to investigate the interaction between soil aggregate, soil organic matter and soil binding agents at aggregate scales. We aim to illustrate the reason of the discrepancies in carbon sequestration efficiencies and propose efficiency ways to improve soil organic carbon content based on our theory.

土壤固碳是提高土壤肥力、应对全球气候变化的重要途径。在农业生产中，提高土壤有机碳的主要方法是施用有机添加物。前期研究发现，施用不同数量有机添加物的固碳效率不同，而传统的土壤固碳理论并不能解释这些现象。基于对不同处理团聚体微结构和土壤胶结物的初步分析，我们提出假设：不同类型/数量有机添加物条件下团聚体发育速度不同，从而形成不同的微生境，影响微生物结构和有机质周转，进而对有机质形成不同程度的物理保护。而有机质的积累速率不同又会影响团聚体发育速度，形成“团聚体发育－有机质积累”的正反馈。同时，有机质与胶结物质具有“协同增加”的效应，促进团聚体发育和有机碳固定。我们拟基于典型红壤长期定位实验，利用同步辐射显微CT等先进技术，从团聚体微结构、有机质和土壤胶结物三个角度开展研究，分析它们的相互关系和相互作用，希望能够阐明土壤固碳效率差异的原因，提出土壤高效固碳的培肥措施，为农业生产提供一些理论参考。

土壤固碳是提高土壤肥力、应对全球气候变化的重要途径。在农业生产中，提高土壤有机碳的主要方法是施用有机添加物。前期研究发现，施用不同数量有机添加物的固碳效率不同，我们提出假设：不同类型/数量有机添加物条件下团聚体发育速度不同，从而形成不同的微生境，影响微生物结构和有机质周转，进而对有机质形成不同程度的物理保护。而有机质的积累速率不同又会影响团聚体发育速度，形成“团聚体发育－有机质积累”的正反馈。本研究基于典型红壤长期定位实验，利用X射线显微CT等先进技术，从团聚体微结构、有机质和土壤胶结物的角度开展研究，分析它们的相互关系和相互作用；同时基于室内培养试验，研究土壤团聚体和土壤孔隙结构对有机碳周转的影响。结果发现不同有机物用量下土壤团聚体发育为不同的结构，高量有机肥处理土壤团聚体大孔隙度提高，小孔隙度降低，团聚体稳定性增加。同时，长期施用有机肥提高了颗粒有机碳（POM C）及矿物结合态有机碳（MAOM C）的含量，施用有机肥降低了SOC的化学稳定性，芳香碳含量及芳香度降低，而烷氧碳含量增加，TG-T50（有机质燃烧一半时对应的温度）降低幅度为10.7~12.0℃，表明长期施用有机肥并非增强了SOC自身的难分解程度，而是主要增强了对SOC的物理保护和化学保护，从而固定SOC。通过室内模拟试验发现，团聚体大小分布对SOC矿化量有显著影响，随着团聚体粒径减小，SOC矿化量显著增加；SOC矿化量与总孔隙度、大孔隙度、充水孔隙度以及充气孔隙度之间存在显著的非线性关系；而土壤孔隙结构也显著影响添加有机物的分解过程。本研究结果表面土壤结构是土壤固碳的重要因素，影响着土壤有机碳周转的各个过程。