Impact of Gully on Soil Moisture of Shrubland in Wind-Water Erosion Crisscross Region of the Loess Plateau*1

The most serious erosion on the Loess Plateau of China exists in the wind-water erosion crisscross region where the annual precipitation is about 400 mm, the ecological environment is very fragile, and water is the key limiting factor for improving the environment. In this study, changes of soil moisture content for Caragana korshinskii Kom. shrubland in the gully bank of the Loess Plateau were studied using the methods of soil sampling and neutron probe. A typical gully (75 m long, 28 m wide, and 10 m deep) was selected, and six neutron probe access tubes (6 m long) were installed at points 50, 100, 200, 300, 400, and 500 cm from the gully border for obtaining soil moisture data from July to October 2004 at approximately 10 d intervals. Soil samplings were simultaneously carried out for moisture determination at the six points. Results showed that the soil moisture of the shrubland in the gully bank significantly varied between 300 and 400 cm in the horizontal direction and up to 600 cm in vertical direction of the gully. Seasonal changes in soil moisture revealed a curve with a single peak that occurred at the end of August or early September. A linear regression equation was fit for soil water storage and the distance from the gully border, with coefficients depending on rainfall characteristics, sampling point, and time of measurement.