Since the Industrial Revolution, human activities have significantly increased atmospheric nitrogen emissions and nitrogen deposition back to the earth surface. With the rapid advancement of industrialization and urbanization, South China has experienced one of the highest rates of global nitrogen deposition. In addition to experiencing a very high nitrogen deposition rate, South China is the main distribution area of evergreen broad-leaved forests in the world. However, how does nitrogen addition affect the carbon and nitrogen metabolism of understory dominant plant species have not been systematically analyzed.

In a research article published in the journal Science of the Total Environment, entitled "Understory and canopy additions of nitrogen differentially affect carbon and nitrogen metabolism of Psychotria rubra in an evergreen broad-leaved forest", researchers from South China Botanical Garden of Chinese Academy of Sciences conducted researches on carbon and nitrogen metabolism and especially flavonoid metabolism in P. rubra under canopy and understory additions of nitrogen treatment.

This study showed that the understroy addition of nitrogen treatment had a greater effect on photosynthesis, amino acid metabolism, and flavonoid biosynthesis than the canopy addition treatment. Most importantly, this research indicated that understory application of nitrogen in experiments may incorrectly estimate the effects of nitrogen deposition on nitrogen and carbon utilization by P. rubra and perhaps by other understory woody plants in the evergreen broad-leaved forests in South China as well.

For further reading, please refer to: https://doi.org/10.1016/j.scitotenv.2020.138183.