Abstract: Taking Yanhe basin as a case, this paper studied the relationships between soil moisture and environmental factors at slope surface, small watershed, and regional scales by using canonical correspondence analysis (CCA). In the basin, slope position and land use type were the main factors controlling soil moisture change at slope surface scale, slope and land use type were the dominating factors at small watershed scale, while evapotranspiration, precipitation, and land use type were the key factors at regional scale, which suggested that with the enlargement of studied spatial scale, the information contained by topographic factors (slope direction, slope position, and slope) gradually converted to climatic factors (evapotranspiration and precipitation), but the information contained by land use type was almost invariant. This study could have significance in studying soil moisture model and hydrological model and their extrapolation.

Key words: rice straw, soil microfauna, soil function, labile resource, greenhouse gas.