Characteristics of Soil Moisture Response to Rainfall under Different Land Use Patterns at Red Soil Region in Southern China

Purpose Studying the response of soil moisture (theta) to rainfall is highly significant for comprehending water transport and balance. Nevertheless, the response of theta to rainfall in pristine forest land and farmland after forest reclamation in the Chinese red soil region is rarely compared.Methods In this study, the theta dynamics and the response characteristics of theta to rainfall in upland field (UF), paddy field (PF), and forest land (FL) were revealed, with continuous and high-frequency theta monitoring data at 5, 10, 20, 40, and 70 cm depths, respectively.Results The results showed that the average theta in PF (0.418 cm(3) cm(-3)) was much higher than that in UF (0.317 cm(3) cm(-3)) and FL (0.291 cm(3) cm(-3)). Meanwhile, the longest lag time (16.8 h) and largest required rainfall amount (16.4 mm) for triggering theta response (RRSR) were observed in FL as compared with UF (11.3 h, 10.2 mm) and PF (12.6 h, 8.7 mm). The maximum increment of theta was significantly positively correlated with the rainfall amount (P < 0.01). The RRSR exhibited significant negative correlations with root density, saturated hydraulic conductivities, and the soil pores content with a diameter > 0.1 mm (P < 0.01). Furthermore, the cumulative increment of soil water storage in FL (190.1 mm) was larger than that in UF (160.6 mm) and PF (143.8 mm).Conclusions The land use conversion from FL to UF and PF reduced the rainfall infiltration capacity and may increase runoff potential.