Study on Soil Hydrothermal Property in Semi-Humid Region of Loess Plateau

Soil hydrothermal property and ground energy balance in semi-humid region of loess plateau were evaluated by utilizing the quality controlled data from Pingliang experimental station.The research indicates that the soil temperature changes from storage type before August and September to expenditure type after August and September,it reverse before and after February.Dry soil layer is found before March2010at 40cm depth,it disappeared after April 2010.This obvious seasonal shallow dry soil layer is the difference with other places.Comparing with Dunhuang in arid desert region and Dingxi in semi-arid region of loess plateau,the net radiation of Pingliang is much higher than Dunhuang,it also a little higher then Dingxi,this suggests that the solar radiation absorptive capacity of Pingliang is larger than that of Dunhuang and Dingxi,it is beneficial to vegetation.Diurnal albedo variation in typical clear day of four seasons shows that change range in winter is the smallest,the summer is the biggest,spring and autumn is between winter and summer.