Objective Mt. Dinghu National Nature Reserve, located in Guangdong Province, is a transitional zone of tropics and subtropics. It provides a unique and important opportunity for climate change studies. The change of precipitation pattern affects the microclimate within a regional forest ecosystem. The research on the characteristics of hydrogen (δD) and oxygen (δ¹⁸O) stable isotope in precipitation and the source of regional atmospheric precipitation are theoretically and practically important to understand the water cycling and community succession in the forest ecosystem of Mt. Dinghu, and wisely use and manage regional water resources.

Method The precipitation δD and δ¹⁸O data in the period from August 2013 to August 2014 were analyzed to examine the relationship between the characteristics of δD and δ¹⁸O and their environmental factors. Furthermore, the air mass transmission pathway was determined and the regional water vapor sources were identified based on HYSPLIT model.

Result The meteoric water line equation is δD = 7.863δ¹⁸O + 9.664 (R² = 0.975, n = 108); the average δD value is-34.44‰, ranging from -118.26‰ to -15.52‰, and the average δ¹⁸O value is -5.58‰, ranging from -16.05‰ to 2.25‰. The atmospheric precipitation excess deuterium (d) follows a seasonal pattern with low value in winter and high value in summer. A "precipitation effect" exists significantly whereas the "temperature effect" is not obvious.

Conclusion There are obvious seasonal changes of δD and δ¹⁸O in atmospheric precipitation in Mt. Dinghu. In dry season, the air mass mainly comes from North China and Eurasia, as well as local evaporation, while in the wet season, the air mass mainly comes from the western Pacific Ocean, the South China Sea, and the Indian Ocean.