Recently, the research project ‘Key nitrogen-use processes of forest plants and their responses to atmospheric nitrogen inputs’ organized by Prof. LIU Xueyan, was funded by Key Project of National Natural Science Foundation of China (NSFC, Grant No. 41730855). The grant period is from Jan. 2018 to Dec. 2022. This project focuses on the environmental issue that China is facing a serious atmospheric reactive nitrogen (Nr) pollution. Combined methods and theories of biogeochemistry, isotopic geochemistry and plant ecophysiology, based on forest ecosystems with different atmospheric N inputs in North China, the project aims at exploring how increasing atmospheric Nr inputs from regional anthropogenic N emissions alter N availability, processes and mechanisms of N utilization in natural plants. The results of this project will provide scientific evidences on evaluating the ecological and geochemical effects of anthropogenic N deposition from the atmospheric system to natural plant-soil systems.