若尔盖退化高寒草甸土壤团聚体结合有机碳的变化

选取若尔盖沼泽化草甸及其不同退化程度为研究对象，利用湿筛法进行团聚体分级，并测定各组分有机碳含量，研究了高寒草甸退化对土壤有机碳(SOC,Soil Organic Carbon)、团聚体以及团聚体结合有机碳(OC,Organic Carbon)的影响，旨在从土壤团聚体及其内部组成的角度去解析SOC的变化特征及机制。结果显示：1)退化使大团聚体比例降低且内部组成改变，团聚体稳定性降低。2)退化使各粒级团聚体及大团聚体内部组分结合OC含量均显著降低。3)大团聚体及其内部粗颗粒有机质中OC储量减少是退化中土壤有机碳流失的主要形式，微团聚体、闭蓄态微团聚体和闭蓄态黏粉粒中OC储量随退化增加。4)退化显著降低了高寒草甸SOC含量和储量，表层(0—10 cm)SOC含量变化主要决定于微团聚体和大团聚体OC含量，亚表层(10—20 cm)SOC含量主要受大团聚体OC含量和团聚体平均重量直径(MWD)影响；对于SOC储量，团聚体MWD是表层SOC储量的最重要影响因素，而亚表层SOC储量取决于团聚体组成、土壤理化性质和大团聚体OC含量的综合作用。研究结果表明，改善土壤团聚体组成和稳定性，增加大团聚体有机...

Changes in soil aggregate-associated organic carbon of degraded alpine meadow in the Zoigê Plateau

Soil aggregate is a basic unit of soil structure. The physical isolation of soil aggregate is the most important mechanism for soil to protect organic carbon from being decomposed by microorganisms. The effects of soil aggregates to maintain the stability of soil organic carbon even exceed the decomposability of organic carbon itself. Meanwhile, the distribution of organic carbon in soil aggregates and the stability of soil aggregate are closely related to the magnitude and stability of soil organic carbon pool, thus they can explain the change in soil organic carbon pool under the changing environment. Zoigê wetland, the most typic plateau wetland in the world, is the birthplace of the Yangtze and Yellow Rivers and stores a large of soil organic carbon. Since the 1960s, the Zoigê wetland has undergone extensive degradation which led to the decomposition of peat and the acceleration of carbon release. However, there are few research on the changes in organic carbon distribution in soil aggregates and its relationship with the changed soil organic carbon pool under alpine meadow degradation. Therefore, we investigated the soil organic carbon (SOC), soil aggregate, and aggregate-associated organic carbon in an alpine meadow and its adjacent degraded sites under the degree of light degradation (LD), moderate degradation (MD), severe degradation (SD), and extreme degradation (ED) in the Zoigê Plateau to explain the mechanism of soil organic carbon pool change and support for the restoration and management of alpine meadow. Wet sieving was used to analyze soil aggregate. The results showed that 1) the aggregate stability and the mass proportion and internal composition of the macroaggregate decreased with degradation, 2) the OC concentration of all size aggregate particles and internal fractions of macroaggregate also decreased with degradation, 3) although the OC stocks in free microaggregate, occluded microaggregate and occluded silt and clay increased with degradation, the decreased SOC was mainly resulted from the decrease of OC stocks in macroaggregate and coarse particulate organic matter, 4) in the surface soil (0-10 cm), the decreased SOC concentration was mainly due to the changes of OC concentration of microaggregate and macroaggregate, while it was the OC concentration of macroaggregate and the aggregate mean weight diameter (MWD) dominating the changes of SOC concentration in the subsurface soil (10-20 cm). Moreover, the SOC stocks in the 0-10 cm soil depth was largely affected by aggregate MWD, but that in the 10-20 cm soil depth was the result of the combination of aggregate structure, soil physicochemical properties and OC concentration of macroaggregate. Overall, improving the composition and stability of soil aggregates and increasing the macroaggregate-associated OC could increase the nutrient supply for plants and the SOC stocks, and ultimately could restore the productivity and function of the degraded alpine meadow.