荒漠草原土壤水分时空变化对降水变化的响应

Response of Spatial and Temporal Variation of Soil Moisture to Precipitation Change in Desert Steppe

为了探讨荒漠草原土壤水分时空变化对降水变化的响应,以毛乌素沙地南缘荒漠草原为研究对象,利用人工遮雨棚和人工补水的方式模拟了5个不同的降水梯度处理(正常降水的33%,66%,100%,133%和166%),采用TDR技术监测0—200cm土层土壤含水量,系统研究了降雨变化对荒漠草原土壤水分滞留规律。结果表明:(1)各降水处理下土壤含水量均在7月份达到最大值,且正常降水处理的土壤含水量高于其他降水处理。(2)不同土层土壤含水量对降雨变化的响应不同,0—40cm土层含水量对降雨量最为敏感,40—80cm土层水分比较稳定,随着土层深度的增加含水量增加,在120—200cm土层水分值最大。(3)不同降水处理之间土壤水分变异系数波动范围较小,深层土壤含水量变异系数值相对较小。(4)降水增加提高了植被密度和生物量。(5)降雨量与土壤水分呈正相关关系;控雨处理下,大气温度与浅层土壤水分呈正相关。因此,全面探讨降水量对荒漠草原土壤水分时空变化的影响,需要考虑降雨季节与土层深度的交互作用,以及区域植被类型的特殊性。

In order to investigate the response of spatial and temporal variation of soil moisture to precipitation in desert steppe,the desert grassland in the southern Mu Us sandy land as the research object,we used the way of artificial awnings and artificial filling water to simulate the 5 different precipitation gradients(33%,66%,100%,133%and 166%of normal precipitation),to monitor soil moisture content in 0—200 cm soil layer by TDR technology,and to systematically examine effect of rainfall on change patterns of soil moisture retention in desert grassland.The results show that:(1)the soil moisture contents in all precipitation treatments reached the maximum values in July,and the soil moisture content in normal rainfall treatment was higher than that in other precipitation treatments;(2)soil moisture contents of different soil layers had different responses to rainfall changes,the moisture content of surface soil(0—40 cm)was the most sensitive to rainfall,soil moisture in 40—80 cm layer was relatively stable,with the increase of soil depth,the water content in the 120—200 cm layer was the largest;(3)the variation coefficient of soil moisture fluctuated in a small range between different precipitation treatments,while the variation coefficient of soil moisture content in deep layer was relatively small;(4)precipitation resulted in the increases of vegetation density and biomass;(5)there was a positive correlation between rainfall and soil moisture;under rain-controlled treatment,atmospheric temperature was positively correlated with shallow soil moisture.Therefore,in order to comprehensively explore the effects of precipitation on the spatial and temporal variation of soil moisture in desert steppe,it is necessary to consider the interaction between rainfall season and soil depth as well as the particularity of regional vegetation types.