Spatial and temporal distribution of soil humidity in karst areas of Guizhou Province

The spatiotemporal distribution, the coefficient of variation of soil moisture and the relationship between soil layers(0-100 cm) in different agricultural climate zones are analyzed, using daily data of soil moisture precipitation and temperature extracted from 53 automatic observation stations in karst areas of Guizhou in the period of 2011 to 2015. The results show that，(1)the ranges of soil moisture in every region are slightly different. According to the 0-100cm deep soil layer’s difference in soil moisture, the soil can be divided into three types, i.e. persistent soil drought, seasonal soil drought and wet soil zones.(2)Similarly, based on the coefficients of variation, the distribution of the soil moisture at profile with the depth range of 0-100 cm in each region can also be divided into consistent variation, seasonal variation, and persistent variation zones. (3)The research on the relationship between 10-50 cm and the soil moisture in the lower layers in karst regions of Guizhou province suggests that upper soil moisture has an effect on the lower layer in warm humid, moderate wet and alpine regions, the upper soil layer has effect on the lower 20-40 cm soil layer but its lower 50-90 cm soil layer is relatively slight. From the sliding days, the days with the maximum correlation coefficients of 10-20, 30-50 and 60-100 cm layer increase with depth in each region, which are 3-10, 10-20, 20-30 days, respectively. (4)Comparing the distribution of soil moisture and its variation coefficient in each region shows that the low value region of soil moisture largely corresponds to the area of large variation coefficient. Besides the direct relationship with precipitation and temperature, the soil moisture may also be related to its soil water holding capacity and other factors.