Soil water distribution before and after a rainfall event at sand dune-interdunes in Horqin Sandy Land, Northern China

In this paper, a typical landscape unit, dune-interdune in Horqin Sandy Land was selected as study object, and the characteristics of soil moisture distribution and rainfall recharge along terrain before and after a moderate rainfall event(22. 6 mm) were analyzed. The results showed that, in the horizontal direction, there were significant differences among the mean soil moisture content(SMC) of 0-90 cm depth at different locations. Before rainfall, the order of SMC at different locations was interdune(10.30%), downslope(1.18%), dune top(0.98%)and upslope(0.75%); after rainfall, the rate of SMC increment was 2.33% for dune top, 3.50%for upslope, 1.77% for downslope and 0.34% for interdune. In the vertical direction, soil moisture distribution with depth before and after rainfall was related with locations. Before rainfall, surface SMC was quite low and mean SMC was slightly higher at 40-100 cm depth of dune top, and at 20-50 cm and 120-200 cm depth of upslope. At downslope and interdune, SMC increased with depth up to saturated values. After rainfall, soil water storage increased at 0-110 cm, 0-110 cm, 0-50 cm and 0-90 cm depth at dune top, upslope, downslope and interdune, which were 12.4%, 13.3%, 9.7% and 14.6% of rainfall, respectively. At 0-10 cm layer, soil water storage increment at interdune was significantly higher than that of dune top and upslope, and there were no significant differences at other layers among different locations(P0.05). During the period with no rain for long time, soil water at dune top and upslope was in deficit, and it is necessary to take measures to maintain a dynamic balance in soil water, which is good for vegetation restoration and desert reversal.