不同土地利用方式下黑土有机碳组分及稳定机制研究

Fully understanding the effect mechanism of soil organic carbon fractions and its stability is the key scientific issues to assess the dynamics and sequestration potential of soil organic carbon. However, the effect mechanism of different soil organic carbon fraction and its stability is still unclear at Mollisols under different land-use types. Soil samples were collected from different plots of grassland, cultivated land and bare land in a long-term field experiment in the black soil region of Northeast China to analyze the dynamics of soil organic carbon concentration and soil carbon fractions under different land-use types using different fractionation method and to study the effect of different land-use types on soil organic carbon stability and temperature sensitivity in different soil aggregates using wet sieving method in this project. Besides, this project also improve the physical and chemical fractionation method of Stewart’s for soil organic carbon to divide the different soil organic carbon fractions with different stability mechanism. Then this project tries to analyze the change trend of mineralization rate and temperature sensitivity of soil organic carbon through short term incubation experiment of obtained soil carbon fractions with different stabilization mechanism. The purpose of this project is to test the hypothesis that the liability of soil organic carbon is uniform across the different stabilizations mechanisms and their turnover times—all stabilize soil organic carbon that decomposes quickly once it is released from protection, and to assess the contributions of different stability mechanisms in stability of soil organic carbon. Results is helpful to promote the overall level of soil organic carbon dynamics and stability studies, and has a great means to evaluate the role of soil in the terrestrial ecosystems carbon cycling and clarify the internal mechanisms of soil organic carbon sequestration and decomposition.

正确认识与理解土壤有机碳稳定性及其影响机制是准确评估土壤碳库动态变化及存储潜力的关键科学问题。本项目针对不同土地利用方式下黑土有机碳组分及稳定性存在差异而影响机制不明确的科学问题，以典型黑土区长期定位试验处理下的草地、耕地和裸地三种不同利用方式的土壤为研究对象，对比分析不同土地利用方式下黑土有机碳含量和组分的差异；研究土地利用方式对不同粒径团聚体结合有机碳稳定性及温度敏感性的影响机理；利用一种改进的土壤有机碳物理-化学联合分组方法，分离出具有不同稳定机制的土壤有机碳组分，结合室内培养技术，对比分析具有不同稳定机制的土壤有机碳矿化速率及其温度敏感性的差异，验证“失去稳定机制的土壤有机碳组分均为不稳定有机碳”这一国际新假说，评估不同稳定机制对土壤有机碳稳定性的贡献。研究结果对阐明土壤有机碳积累和分解的内在控制机理及正确评价土壤在陆地生态系统碳循环中的作用具有重要意义。

土地利用和管理是人类影响土壤最重要、最直接的活动，它通过不同的利用方式和利用强度影响着土壤中众多的生态过程，进而导致土壤有机碳的组分和稳定性发生显著变化。本项目以不同土地利用方式下的土壤为研究对象，对比分析不同土地利用方式下土壤有机碳含量和组分的差异；研究土地利用方式对不同粒径团聚体结合有机碳组分、稳定性及温度敏感性的影响机理；采用物理-化学联合的土壤有机碳分组方法，分离出具有不同稳定机制的土壤有机碳组分，结合室内培养技术，对比分析具有不同稳定机制的土壤有机碳矿化速率的差异，探讨稳定机制对土壤有机碳稳定性的影响。结果表明：（1）各土地利用方式下，土壤有机碳含量及组分均随着土壤深度的增加呈显著（P < 0.05）的下降趋势。在四个土壤易氧化有机碳组分中，极不稳定有机碳组分占总有机碳含量的比例（40%左右）最高。土地利用方式对土壤有机碳含量和组分均具有显著（P < 0.05）影响，且对表层土壤有机碳含量和组分的影响大于下层土壤。（2）各土壤团聚体中，大团聚体（> 250 μm）结合有机碳及组分的含量要显著高于微团聚体（53-250 μm）和粉黏粒团聚体（< 53 μm）。与微团聚体和粉黏粒团聚体相比，大团聚体结合有机碳的矿化速率及累积矿化量明显较高。旱田中微团聚体和粉黏粒团聚体结合有机碳矿化的温度敏感性比水田分别增加了17.1%和13.8%，而全土和大团聚体中的差异较小。（3）稳定机制去除后土壤有机碳含量发生了显著变化，其中矿物机制的去除使各组分中土壤有机碳的含量提高了近8倍，而Fe机制的去除使各组分中土壤有机碳的含量降低了约22%。稳定机制去除改变了各土壤组分结合有机碳的矿化速率及累积矿化量，但不同利用方式下不同组分的影响程度有所区别。研究结果对阐明土壤有机碳积累和分解的内在控制机理及正确评价土地利用方式变化对土壤碳循环的影响具有重要意义。