Effects of forest vegetation on soil moisture and runoff of watershed in east China

hydrological effects of natural secondary forest ecosystem were studied from March to October in 2009. The results showed that soil moisture ranged from 14.24% to 22.55% in observation period. The monthly variation trend in soil moisture of top layers (5cm and 10cm) was similar to that of rainfall. Deep layers (20cm and 50cm) moisture became gradually stable as the depth increasing. The soil moisture of 10cm layer was obviously higher than that in other three layers. Runoff analysis showed that the annual runoff ratio in this research watershed is 68.5%, but the ratio for quick runoff, composed of direct runoff and surface runoff, is only 0.10%. The total watershed runoff during this period was 836.5 mm. It was shown that the amount of surface runoff increased with the increasing of precipitation, but having various tendencies for different precipitation intensity classes.