Effect of land use and topography on spatial variability of soil moisture in a gully catchment of the Loess Plateau, China

Abstract

The Loess Plateau ecosystem in China is degraded owing to poor natural conditions and intense human activity. The intensity of soil erosion and deficit of soil moisture are the key factors that influence the ecological restoration and agricultural land productivity in this region. Analysis of the soil moisture dynamic and the relative importance of land use and topography for the spatial variability of soil moisture is the basis for guiding ecosystem restoration and agricultural development. We analysed the spatial variability of soil moisture for five land-use types within 44 sample plots (176 sample points) at the five depths (0-20, 20-40, 40-60, 60-80 and 80-100cm) in the Anjiagou catchment of the Loess Plateau from April to September 2002. The depth-averaged soil moisture of cropland was the highest among the five land-use types, followed by fallowland, woodland, shrubland and wasteland during high soil-water contents period (from 24 April to 23 June). The time-averaged soil moisture of all the five land-use types first decreased with depth during the wet moisture status and then increased with depth during the dry conditions (from 12 July to 9 August). The time-averaged soil moisture of fallowland, cropland and shrubland was decreased with depth, but both wasteland and woodland was decreased and then increased with depth in the medium moisture status (from 23 August to 18 September). Land use was the key factor that influenced the spatial variability of the time-averaged moisture of the four soil layers (20-40, 40-60, 60-80 and 80-100cm) during the wet and medium soil-water content condition. Land use had a weak influence on the spatial variability of the time-averaged moisture of all the five soil layers in the dry moisture status. Slope aspect had a significant influence on the time-averaged soil moisture of some soil layers in the wet and medium moisture statuses for wasteland, shrubland, woodland and fallowland. The other four topographic factors (slope profile curvature, slope position, relative elevation and slope gradient) all had weak influence on the time-averaged soil moisture of all the five land use types in the three water statuses. © 2011 John Wiley & Sons, Ltd.