Influence of meteorological factors on the dynamic changes of soil moisture of natural grassland in the northern slopes of the Mountains Qilian

We conducted a field study by regression and correlation analysis to examine the relationships between soil moisture and meteorological factors for five kinds of grassland in the northern slopes of the Mountains Qilian;and soil moisture was collected from the study site along with synchronous meteorological data in 2004 for analysis.The results showed that(1) Dynamic change of soil moisture was determined by precipitation and its seasonal distribution,and regression equation between precipitation and soil moisture were set up.(2) The potential evapotranspiration of five types of grassland was analysed based on ASCE-PM model.The relationship between potential evapotranspiration and soil moisture in 0～20 cm soil layer was significant(P0.05).But there was no correlation between potential evapotranspiration and other soil layers.(3) Air temperature,soil temperature,relative humidity and near-ground wind speed exert an influence on soil moisture,and the responses of soil moisture to these factors were descending along the soil layer depth.