Human activities have significantly increased atmospheric nitrogen emissions and nitrogen deposition, such that atmospheric nitrogen deposition has become a major focus of environmental science and policy. Because nitrogen deposition is a global problem, the effects of nitrogen deposition on forest plants have been widely studied. The effects of nitrogen deposition on carbon metabolism, distribution, and regulatory processes, however, have not been systematically analyzed.

In a research article recently published in the journal Science of the Total Environment, entitled "Canopy and understory additions of nitrogen change the chemical composition, construction cost, and payback time of dominant woody species in an evergreen broad-leaved forest", researchers from South China Botanical Garden of Chinese Academy of Sciences conducted researches on forest plant carbon metabolism dynamics under canopy and understory additions of nitrogen treatment.

They found that compared with the control, leaf chemical compositions of these plants were differentially changed by canopy and understory additions of nitrogen. These changes were accompanied by significant changes in maximum photosynthetic rates, construction costs, and payback time of different forest plants. Correlation analyses showed that the changes in protein and structural carbohydrate contents helped explain the changes in payback time.

This study further revealed that nitrogen deposition may increase carbon assimilation and allocation in shrubs and small trees, and large trees may require a longer period to increase carbohydrates, which may help explain the ongoing transformation of evergreen broad-leaved forests into shrublands.

For further reading, please refer to: https://doi.org/10.1016/j.scitotenv.2020.138738.