Soil moisture response to environmental factors following precipitation events in a small catchment

Abstract

Moisture variation in upper soil layers following a precipitation event is recognized as an important process in the conversion of rainfall to soil water. To understand the variability of topsoil moisture following a period of precipitation, we explored changes in soil moisture after 12 precipitation events at 38 sampling locations in the Wulongchi catchment (1.92km2) located in the Danjiangkou Reservoir Area, China. Our results indicated that variation in soil moisture increased with decreasing soil moisture following each of the 12 precipitation events. Using a two-way indicator species analysis (TWINSPAN), the soil moisture measurement periods following each event were classified into three discrete groups: humid periods, moderate periods, and dry periods. For the humid periods, the total variance of soil moisture that could be explained by redundancy analysis was more consistent than those of the moderate and dry periods. For the humid periods on the first axis, soil thickness was the main significant factor, and the topographic wetness index, slope position and aspect were also significant environmental factors. For the moderate and dry periods, however, the effect of aspect on soil moisture decreased, whereas the effect of relative elevation increased. Each environmental factor that was tested for its influence on topsoil moisture variation presented different effects throughout all three of the studied soil moisture periods.