Abstract: [Objective] In order to provide scientific evidences for understanding the process of water cycle of forest ecosystem and managing regional water resources under the varying precipitation pattern in Dinghushan National Nature Reserve in the south subtropical zone of China.[Method] In this study, the δ D of soil water and the potential water sources including precipitation and shallow underground water were analyzed to determine the source of soil water and the distribution of different intensity precipitation in the soil profile of the monsoon evergreen broad leaved forest in Dinghushan National Nature Reserve, using deuterium isotope technique. The contribution of precipitation in each layer of the soil profile was calculated by binary linear mixed model.[Result] The soil water δ D was found between those δ D values of precipitation and shallow underground water, indicating that precipitation and shallow underground water were the sources of soil water in the monsoon evergreen broad-leaved forest in Dinghushan National Nature Reserve. After a 5-day small rainfall (9.8 mm), the contribution rate to surface soil layer (0-10 cm) was the highest (31.2%-44.6%), followed by the layer of 10-40 cm (24.2%-32.0%) and the soil layer of 40-80 cm (8.3%-15.7%), and the soil layer of 80-100 cm was the lowest, close to zero. With a moderate rainfall event of 20.0 mm, the contribution rate to surface soil (0-10 cm) was the highest (63.3%-78.9%), followed by the soil layer of 10-40 cm (46.9%-74.0%) and the layer of 40-80 cm (37.9%-63.0%), and the soil layer of 80-100 cm was the lowest (35.8%-47.5%). The precipitation infiltrated the deep soil (>80 cm) and the contribution to the soil layer of 80-100 cm under heavy rainfall (>30 mm) was 94.1% during the same day either in the wet season or in the dry season.[Conclusion] The results showed that δ D of surface soil water (0-10 cm) was mainly controlled by rainfall δ D. The faster the precipitation moving from the soil surface to the deep soil, the more obvious the effect of soil δ D on the depth of 80-100 cm and the greater the rain contribution to the soil water at all levels with increasing the precipitation intensity. Deep soil water (80-100 cm) δ D value was basically kept stable under the small rainfall event of ≤ 20 mm. The results illustrated that vegetation structure of the monsoon evergreen broad-leaved forest in. Dinghushan National Nature Reserve played an significant role in regulation of the precipitation infiltration in the soil profile.

Key words: deuterium isotope, precipitation, soil water, monsoon evergreen-broad leaved forest, Dinghushan National Nature Reserve, water source