青海湖区天然草地和农田土壤水分变化特征

Characteristics of soil moisture change in natural grassland and farmland in the region around Qinghai Lake

对环青海湖地区天然草地和农田土壤重量含水率年际、年代际和年内动态变化进行气候趋势系数法、气候倾向率法和变异系数法等分析,结果表明：环青海湖地区天然草地与农田同期土壤含水率年际变化趋势相反。1997年以来,0-50 cm土壤含水率年际变化农田呈显著或极显著增大趋势,增大幅度3.062%·10a-1-10.848%·10a-1;天然草地土壤含水率均呈减少趋势,减少速率中间土层快上下慢,但趋势不显著;20世纪末本世纪初和2004—2010年两个时段农田土壤含水率增大,天然草地土壤含水率减少趋势极显著体现在前一阶段,而近年来增减趋势不显著,各层次土壤含水率平均值均大于前一阶段,但牧草生长高峰期夏季变小。农田和草地土壤含水率年内变化相同,春季土壤含水率相对较高,其后极显著下滑,农田由于耕作性失墒等影响,土壤含水率下滑幅度大于草地。

The methods of climate tendency coefficient,climate tendency rate and coefficient of variation were adopted to analyze the interannual,interdecadal and annual dynamic changes of soil moisture content in natural grassland and farmland in the region around Qinghai Lake. The results showed that the annual variation trend of soil moisture content in natural grassland and farmland during same period was contrary. Since 1997,the annual variation of soil moisture content in 0 - 50 cm in farmland presented a significant or extremely significant increasing trend which ranged from 3. 062% ·10a-1to 10. 848% ·10a-1,while that in natural grassland presented an insignificant decreasing trend whose rate was high at the middle stage and low at the early and late stage. The soil moisture content was increased at the turn of 20th and 21st century and during the years from 2004 to 2010. The decreasing trend of soil moisture content in natural grassland was remarkably reflected in the previous stage,and there was no obvious increase or decrease in recent years. The average value of soil moisture content in various depths was wholly greater than that in the previous stage,but it became small in summer when was the growth peak period of grass. The seasonal change of soil moisture content in grassland and farmland was the same. It was relatively high in spring and then became decreased obviously. The decreasing range of soil moisture content in farmland was larger than that in grassland because of cultivability loss of water.