植被退化对高寒土壤水文特征的影响

The Impact of Vegetation Degeneration on Hydrology Features of Alpine Soil

在黄河源冻土严重退化地区,采用选择典型区域和样地进行实验和模型模拟的方法,对不同植被退化特征条件下高寒土壤的水分特征曲线、土壤饱和导水率、土壤入渗及土壤水分进行研究.结果表明:Gradner和Visser提出的经验方程θ=AS-B对该地区土壤水分特征曲线有良好的模拟性;不同植被盖度条件下土壤的饱和导水率和土壤入渗有明显的区别,表层0～10cm范围内,黑土滩的饱和导水率和入渗强度最强,30cm以下土层中土壤饱和导水率、入渗强度以及土壤含水量几乎不受植被的影响.随植被退化表层土壤含水量出现明显降低,退化越严重,水分流失越多,最多时能达到38.6%,植被根系最发达的10～20cm范围的土壤含水量流失对高寒草甸土壤环境影响最大,水分流失导致退化草甸恢复难度较大.通过比较研究,在黄河源地区考斯加科夫(Kostiakov)入渗公式f(t)=at-b更适用于该研究区域高寒草甸土壤水分入渗过程的研究.

Alpine soil infiltration process is an important part of hydrological features of the alpine soil in permafrost regions.The research is carried out in the source regions of the Yellow River,where permafrost is degrading severely,with the methods of choosing typical areas and quadrats to do experiment and simulation and then to study the soil water characteristic curves,soil saturated hydraulic conductivities,soil infiltrations and soil moistures under different characteristics of degraded vegetation.The results show that the empirical equation θ=AS-Bproposed by Gradner and Visser has a good simulation of the soil moisture characteristic curves;soil saturated hydraulic conductivity and soil infiltration have significant difference under different vegetation coverage：in the soil surface within 0～10cm in depth,the saturated hydraulic conductivity and infiltration intensity of the black beach are the maximum;in the soil layers 30cm below the surface,vegetation has almost no impact on the saturated hydraulic conductivity,infiltration intensity and soil moisture content.Remarkable reduction of soil moisture occurs in the soil surface with the degradation of vegetation.The more serious the degradation is,the more the water loss.The water loss can be up to 38.6% in the worst situation.The soil moisture in the depth between 10cm and 20cm,where vegetation root systems develop well,has the greatest impact on the soil environment.Thus the loss of moisture in the depth between 10cm and 20cm will induce restoring the degraded meadow hardly.Through a comparative study,it is found that Kostiakov infiltration equation f（t）=at-b is more applicable to study the process of soil moisture infiltration of the alpine meadow in the source regions of the Yellow River.