Abstract: Three soil types including sandy soil, residual soil of weathered bedrock and sierozem were used to equip a device of controlling rainfall, record soil moisture content by an installed American HOBOU 30, and monitor the long-term dynamic change of soil moisture content. The purposes of this study were to research the spatial and temporal dynamic changes of moisture content of different soil types in desert steppe and its response to precipitation variation. The results showed that the temporal variation of volumetric moisture content of sand soil, residual soil of weathered bedrock and sierozem were affected by rainfall, and three peak values occurred. Rainfall change affected the peak values to appear sooner or later. There were two major types of vertical change of soil volumetric moisture content, i.e. the fluctuation type and reduction type. They were mainly affected by surface vegetation and soil physical properties. The variation coefficients under the normal situation and the rain-reduced treatment of sandy soil and residual soil of weathered bedrock were decreased from the surface to the deeper layer. The variation coefficients of volumetric moisture content of sierozem were 1.21%, 1.36% and 1.46% under the normal situation, rain-increased treatment and rain-reduced treatment respectively. Under the normal situation and rain-increased treatment, the total soil water storage was in an order of residual soil of weathered bedrock>sandy soil>sierozem; under the rain-reduced treatment, however, it was in an order of residual soil of weathered bedrock>sierozem>sandy soil.

Key words: desert steppe, soil moisture content, precipitation variation, soil type, Ningxia