中文摘要：

揭示干旱、半干旱地区生态系统土壤水分动态对于进一步认识生态系统过程与功能机制,提出应对气候变化影响的途径均具有重要意义。以小针茅草原为对象,基于连续4 a逐时监测的土壤含水量（地表以下15 cm）与降雨数据,结合邻近气象站过去50 a的降雨资料,探讨了荒漠草原土壤水分动态规律及其对降雨的响应。结果表明：①受降雨分布格局的影响,荒漠草原土壤水分动态存在单峰型和双峰型两种模式;②地表以下15 cm处的土壤水分对5 mm以下降雨事件没有响应,18 mm以上的降雨对该土层土壤水分才具有较强的补充作用,土壤所需的降雨量比沙地和荒漠区更高;③降雨量越大、降雨强度越大或降雨前土壤含水量越高,土壤水分对降雨的响应就越迅速。未来气候变化可能对荒漠草原区浅根型植物生长不利,从而对畜牧业生产产生重要影响。

英文摘要：

It is crucial to further understanding the mechanism of ecosystem process and functions,and proposing the ways to cope with the effects of climate change through revealing the dynamic change of soil moisture content in arid and semiarid ecosystems. In this study,the dynamic change of soil moisture content and its response to rainfall were explored using the precipitation data in recent 50 years from a nearby meteorological station based on the data of soil moisture content（ 15 cm in depth） and of precipitation in recent continuous 4 years in a steppe. The results are as follows：① Affected by precipitation distribution pattern,the curves of dynamic change of soil moisture content in the steppe were unimodal and bimodal; ② There was no response of soil moisture content to rainfall less than 5 mm. However,the soil moisture content could be significantly increased when rainfall was more than 18 mm.Moreover,rainfall needed by soil was higher than that by sandy land and desert; ③ Response of soil moisture content to rainfall was rapid when rainfall and its intensity was high or soil moisture content was high before rainfall.Climate change in the future will possibly be disadvantageous for the growth of shallow rooting plants,thus it will impact seriously the animal husbandry.