Time Series Analysis of Spatial Variability of Soil Moisture in Loess Hilly Region

The seasonal spatial variability of soil moisture in loess hilly region was studied by using geo-statistic and classical statistic method. The results show that: (1) The spatial variability of soil moisture had middle variable characteristics in different periods. (2) The soil moisture of each layer shows strong fluctuation in rainy seasons: before or after the start of the rainy seasons, the soil moisture first increased and then decreased, which shows slight changes. (3) Before the rainy season, the spatial variability of soil moisture along northwest-southeast is the highest, while that along north-south is the highest in the rainy seasons. After the rainy seasons, the spatial variability of soil moisture along east-west was the highest and it has good autocorrelation. Soil moisture in different seasons presents zonal anisotropy. (4) The soil moisture has strong spatial correlation after the rainy season while that in the rainy seasons or before it is weak. (5) Land use type and soil bulk density has great effect in the spatial variability of soil moisture in sampling seasons. Besides, slope is major influential element in the rainy season and after it. (6) As seasons change, the draught center in Yanhe basin turns from surfaces to points in rainy seasons and turns from points to surfaces after rainy seasons. The soil moisture in Yanhe basin showed differences in south and north.