三江源区高寒草甸不同退化演替阶段土壤有机碳和微生物量碳的变化

Changes in Soil Organic Carbon and Microbial Biomass Carbon at Different Degradation Successional Stages of Alpine Meadows in the Headwater Region of Three Rivers in China

以野外样地调查和室内分析法研究了三江源区高寒小嵩草草甸不同退化演替阶段群落中土壤有机碳和微生物量碳的变化．结果表明，放牧活动明显地影响了土壤有机碳和微生物量碳的含量．不同退化演替阶段期间，高寒小嵩草草甸土壤有机碳、微生物量碳含量在0～10cm土层明显较高，且随着退化程度的加剧，分布在0—40cm土层的土壤有机碳、微生物量碳含量明显降低；不同退化演替阶段，高寒小嵩草草甸由于家畜过度的啃食与践踏，不仅使得植物群落发生了逆向演替，而且土壤的肥力水平显著地下降，土壤向退化方向发展；高寒草甸的退化将使土壤有机质大量流失，氮素损失严重．随着退化演替过程的进行，高寒草甸土壤质量和土壤营养的持续供给能力逐渐退化，土壤有机碳和土壤微生物量碳含量也随放牧强度增加而迅速降低；相关分析表明，土壤有机碳和土壤微生物量碳与土壤含水量、土壤有机质、土壤速效氮呈显著正相关关系（P〈0．05），说明土壤微生物量碳可作为衡量土壤有机碳变化的敏感指标，而土壤有机碳和微生物量碳含量可作为衡量土壤肥力和土壤质量变化的重要指标。

Alpine meadow ecosystem is one of the important grassland resources for grazing on the Tibetan Plateau. The methods of field survey and experiment analysis were applied to detect the changes in soil organic carbon （SOC） and soil microbial biomass carbon （MBC） of alpine meadows at different degradation successional stages in the headwater region of three rivers. The results showed that the contents of SOC and MBC were higher in 0 - 10 em soil layer at different degradation successional stages, the contents of SOC and MBC in 0 -40 em soil significantly decreased with aggravating degradation of the meadows the and the percent vegetation cover and biomass percent of palatable herbage were correspondingly shown to decrease across meadows in the region. Soil quality and soil nutrition were decreasing with the increasing of soil degradation, SOC and MBC contents decreased rapidly with increasing grazing density. There was significant correlation between the two indices on soil organic matter, soil moisture and soil available N, indicating that both SOC and MBC could be used as the important indicators to measure the changes of soil quality. Fig 2, Tab 4, Ref 29