祁连山黑河上游多年冻土区不同植被类型土壤有机碳密度分布特征

山地多年冻土的异质性影响其植被类型的分布特征，且对有机碳的分布也具有重要影响。通过采集黑河上游多年冻土区三种典型植被类型（高寒沼泽草甸、高寒草甸、高寒草原）8个活动层的土壤样品，测定其土壤有机碳密度及其理化性质。结果表明：高寒沼泽草甸土壤有机碳密度最高（49.50 kg·m^-2），高寒草甸次之（11.22 kg·m^-2），高寒草原最低（7.30 kg·m^-2）。土壤有机碳密度的剖面垂直分布特征具有差异性，高寒沼泽草甸土壤有机碳密度随深度变化不明显，高寒草原和高寒草甸土壤有机碳密度随深度逐渐减小，存在显著的表层聚集性。有机碳密度与土壤含水率和细粒含量呈显著正相关，与pH值呈显著负相关关系。一般线性模型结果表明土壤含水率、pH值和土壤颗粒组成解释了96.39%的有机碳密度变异，其中土壤含水率贡献了81.53%，pH值和土壤粒度分别贡献了9.33%和4.75%。研究表明多年冻土区不同植被类型土壤有机碳密度分布特征具有明显差异，山地多年冻土土壤含水率是控制有机碳密度分布特征的重要影响因素。

Distribution features of permafrost organic carbon density on different vegetation types in the upper reaches of Heihe River,Qilian Mountains

The heterogeneity of mountain permafrost affects the alpine vegetation type and have an effect on the distribution of soil organic carbon (SOC). In this study, the SOC densities and soil physical and chemical properties were measured on soil samples, which sampled from eight active layers within three types of vegetation cover (swamp meadow, alpine swamp meadow and alpine steppe). It was found that the average SOC density was highest in alpine swamp meadow (49.50 kg·m^-2), following by alpine meadow (11.22 kg·m^-2), and in alpine steppe it was the lowest (7.30 kg·m^-2). In a vertical profile of SOC density, there was a slightly difference:no obvious variation in alpine swamp meadow, decreasing with depth in alpine meadow and alpine steppe, with a significant aggregation in surface. There were positive relationships between SOC density and soil moisture, silt and clay content, and a negative relationship between SOC density and pH value. General linear model result shows that the soil moisture content, pH value and soil particle composition are able to explain 96.39% of the organic carbon density variation, of which 81.53%, 9.33% and 4.75% are attributed to soil moisture, pH value and soil texture, respectively. It means that soil moisture plays a key role in distribution of SOC density in alpine permafrost regions.