Impact of terrain factors on soil moisture in slopes of western Shanxi Province in loess area

The impacts of terrain factors on soil moisture in different slopes in the research area of the Caijiachuan Watershed, Jixian County, Shanxi Province were studied through deriving slope, aspect and elevation maps from Digital Elevation Model (DEM) and overlaying them with soil moisture maps (KRIGING interpolation approach). The main results from factor analysis showed that the effects of terrain factors on soil moisture at different depths of the soil profile varied. At a depth of 0--30 cm, the slope direction is the predominant factor, then elevation and the last factor is slope degree; but at 30--60 cm, slope is the most important factor, then elevation and aspect. Taking the main impact factors (slope and aspect) as an example: this paper analyzed the effects of these factors on soil moisture in detail, based on a single-factor analysis approach. The result shows that aspect impacts the soil moisture significantly; soil moisture is the highest at N337.50°, lowest at N202.50°(0-30 cm) and N191.25°(30--60 cm) and is closely correlated with aspect (twice simultaneous decline-increase). Soil moisture changes little with slope and shows a tendency of increase-decline-increase with an increase in slope.