Spatial variability of soil moisture on hillslope in typical karst peak-cluster depression areas

The study area is located in Guilin, Guangxi, with a land area of approximately 3,000 m2. The area is characterized by humid subtropical monsoonal climate, with the average annual temperature 18.7 ℃ and the average annual rainfall of 1，785.2 mm; and it’s rainy season is generally from April to September, which belongs to the typical karst peak-cluster depression landforms. The study area include the hillslopes and the below terraces, and the terraces were previously transformed from hillslopes and used by villagers for the orangery and vegetable gardens. The exposed rate of rock in the middle of the hillslopes is more than 70%; and a large amount of exposed rock divide their soil into patches in the form of "rock gap soil" and "stone bowl soil" while retaining the upper native shrub. In order to reveal the spatial variability characteristics of surface soil moisture in typical karst peak-cluster depression hillslopes with strong artificial disturbance and land use diversity, selecting the slopes of the typical peak-cluster depressions and using grid method to measure the soil moisture content in the dry season (December) and the rainy season (May)， the spatial variability of soil moisture on hillslopes was analyzed by geostatistics. The results show that,(1) Compared with the slope of single land use，the surface soil moisture of the typical peak-cluster hillslopes is that undisturbed natural vegetation area located above the slope is significantly higher than artificial transformation of the region located below the slope，soil water content of sloping woodland(32.8%)that locating on top of the slope and undisturbed was significantly higher than terraced fields (24.2%) , terraced orange garden (20.0%)，terraced vegetable garden (22.0%) and bare land (23.5%) during the dry season. In rainy season，bare land (30.2%) and terraced origin garden (32.1%) had increased obviously and the terraced fields were drastically reduced (17.8%)，while sloping woodland (32.2%) remained the highest；(2)The spatial structure ratio is 21.0% and 8.7% during the dry and rainy season, respectively, indicating that the spatial correlation of the rainy season is better；the coefficient of variation of the surface soil moisture was 20.1% and 31.7% during dry season and rainy season，which are both belonging to moderate spatial variability；the range of surface soil moisture during the rainy season (77.5 m) was significantly higher than that of dry season (8.0 m), which can be seen that the spatial variation structure of rainy season is better； (3)The change of soil moisture in the surrounding space of bare stone decreases with the increase of distance；soil moisture in the surrounding space of terrace bank is decreasing with increasing distance.