青海海晏县西海镇沙柳林地土壤水分研究

Soil moisture of Salix psammophila land at Xihai Town in Haiyan County,Qinghai Province

根据对西海镇土壤含水量、孔隙度与粒度测定，研究了沙柳树林土壤含水量和水循环等问题。结果表明，研究区在丰水年土壤上部含水量丰富，土壤0．1～1．0m的平均含水量为21．3％，1．0m以下水分明显不足，土壤水分具有在上部滞留的特点。大约1m深度处土层开始出现轻度干层，1．3～1．6m出现了中等干层，1．6m深度以下出现了严重干层。干层发生原因一是降水量少，二是沙柳林的蒸腾消耗。该区土壤干层的发育阻隔了大气降水向地下深处的入渗，属于异常水分循环类型。该区土壤水分处于负平衡状态，指示当地正常年的降水量并不能充分满足沙柳林生长的需要。西海镇土壤蓄水量较少，易于发生生态环境的退化。该区土层0．1—1．0m以粉砂为主，1．0m以下是细砂为主的中砂细砂土。

By soil moisture content, porosity and particle composition experiments at Xihai Town, we studied the soil moisture changes of Salix psammophila land. The result shows that, the soil moisture content in upper layers is high, the average moisture content between 0.1 m and 1.0 m is 21.3%, but there are serious water shortage in lower layers with the characteristics that soil moisture is stranded in the upper layers. There exist mild dried layer at about lm depth, medium dried layer at about 1.3 m to 1.6 m and severe dried layer below 1.6 m. The poor precipitation in Xihai Town is the main reason for medium and partially severe dried layers, besides, the transpiration consumption of Salix psamrnophila is another reason for that. The developing of dried layer cut off the infiltration of rainfall into lower soil layers, which belongs to abnormal moisture cycling types. The negative water moisture balance indicates that the rain water can not meet the need for forest development and afforestation. The poor water storage capacity of soil at Xihai Town may result in degenerating of ecoenvironment. The upper soil layers between 0.1 m and 1.0 m is mainly composed of silty sand, below 1.0 m is composed of fine and medium sand, mainly is fine sand.