若尔盖退化高寒草甸土壤团聚体结合有机碳的变化

Selecting the Zoige swampy meadow and its different degradation degrees as the research objects, using the wet sieving method for aggregate grading and determining the organic carbon content of each component, the impacts of alpine meadow degradation on soil organic carbon (SOC), aggregates and aggregate-bound organic carbon (OC) were studied, aiming to analyze the changing characteristics and mechanisms of SOC from the perspective of soil aggregates and their internal compositions. The results showed that: 1) Degradation decreased the proportion of macro-aggregates and changed their internal compositions, and the stability of aggregates decreased. 2) Degradation significantly decreased the OC content bound to each particle-size aggregate and the internal components of macro-aggregates. 3) The decrease in OC storage in macro-aggregates and their internal coarse particulate organic matter was the main form of soil organic carbon loss during degradation, and the OC storage in micro-aggregates, occluded micro-aggregates and occluded clay-silt increased with degradation. 4) Degradation significantly decreased the SOC content and storage in alpine meadows. The change in SOC content in the surface layer (0 - 10 cm) was mainly determined by the OC content of micro-aggregates and macro-aggregates, and the SOC content in the sub-surface layer (10 - 20 cm) was mainly affected by the OC content of macro-aggregates and the mean weight diameter (MWD) of aggregates; for SOC storage, the aggregate MWD was the most important influencing factor for the SOC storage in the surface layer, while the SOC storage in the sub-surface layer depended on the combined effects of aggregate composition, soil physical and chemical properties and the OC content of macro-aggregates. The research results indicated that improving the composition and stability of soil aggregates and increasing the organic carbon of macro-aggregates may be an important way to improve soil nutrient supply, increase the level of soil organic carbon, and thus restore the productivity and function of degraded grasslands.

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,增加大团聚体有机碳可能是提高土壤养分供应,提升土壤有机碳水平,从而恢复退化草地生产力和功能的重要途径。