不同退化程度高寒草甸土壤团聚体及其有机碳分布特征

为探究退化对高寒草甸土壤质量的影响，在甘肃省天祝藏族自治县金强河高寒草甸范围内设置未退化、轻度退化、中度退化、重度退化4个退化梯度，采用干筛法研究了不同退化程度高寒草甸0～30 cm土层土壤团聚体及其有机碳分布特征。结果表明：粒径>5 mm的团聚体含量随退化加剧显著降低，<0.25 mm粒级团聚体含量随退化加剧显著升高。大团聚体含量、平均重量直径及几何平均直径随退化加剧逐渐降低。团聚体有机碳含量随退化加剧呈先增加后降低趋势，大团聚体中0.25～0.5 mm粒级团聚体有机碳含量最高，各粒级团聚体有机碳含量均随土层加深而降低。未退化草地对有机碳的贡献率主要是> 5 mm粒级的团聚体，退化加剧，<0.25 mm的微团聚体对有机碳的贡献率逐渐升高。双因素分析表明退化程度与土壤深度的交互作用对团聚体分布、团聚体有机碳含量及有机碳贡献率有显著影响。草地退化导致土壤结构稳定性下降，大团聚体占比降低，对有机碳的贡献率减小。研究结果可从土壤团聚体及有机碳角度对退化草地的治理及可持续利用提供理论指导。

Distribution Characteristics of Soil Aggregates and its Organic Carbon with Different Degradation Degrees in Alpine Meadow

To explore the effects of different degradation degrees of alpine meadows on soil quality,four degradation gradients of no degradation,light degradation,moderate degradation and severe degradation were set up in Jinqianghe meadow in Tianzhu County,Gansu Province. We used dry-sieving method to study the soil aggregates and organic carbon distribution characteristics of different degraded alpine meadows of the 0~30 cm soil layer. The results showed that degradation of alpine meadows reduced the content of the size of >5 mm aggregates,while increased the content of the size of<0.25 mm aggregates.The differences between no degraded and degraded meadows were significant. With the increase of degradation,the proportion of large agglomerates (R_0.25),mean weight diameter (MWD) and geometric mean diameter (GWD) all gradually decreased. The organic carbon content in soil aggregates tended to increase and then decrease with the increasing degradation. The highest organic carbon content of aggregates was found at the 0.25~0.5 mm granular aggregates.,The organic carbon content of aggregates in different degradation gradients decreased with deepening of the soil layer. A similar pattern of variation existed between the contribution of soil agglomerates to organic carbon and the distribution of agglomerate content. Two-way AVOVA showed that the interaction between degradation degree and soil depth had significant effects on the aggregate distribution,aggregate organic carbon content and organic carbon contribution rate,but had no significant effects on the aggregate stability. Grassland degradation led to the decline of soil structural stability,the proportion of large aggregates decreased,and the contribution rate of organic carbon decreased. The results provide some theoretical guidance for the restoration and sustainable development of degraded grasslands.