East Asia has become one of the three largest nitrogen deposition centers in the world after Europe and North America. Excessive nitrogen is thought to be one of the drivers of biodiversity change across the globe, and nitrogen deposition can also cause acidification of soils and water. Consequently, it is important to study the carbon-nitrogen cycle in East Asia.

Prof. DAN Li from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences and his colleagues incorporated the full nitrogen cycle - including deposition, mineralization, immobilization, biological fixation, nitrification, denitrification, volatilization, and leaching of nitrogen - into a land surface model called Atmosphere-Vegetation Interaction Model (AVIM).

The model was designed and developed by Chinese scientists and was one of the earliest models to consider the dynamical process of vegetation. The latest version of AVIM has been run over China between 1979 and 2015 at a resolution of 10 km. The results were published in Atmospheric and Oceanic Science Letters.

According to this study, gross primary production and net primary production were simulated well by AVIM across China when compared to carbon flux data from MODIS and the ensemble mean data of Trends in Net Land-atmosphere Carbon Exchange (TRENDY).

The nitrogen deposition and biological fixation were also well simulated at the regional scale. However, the variation in carbon and nitrogen fluxes showed discrepancies in different datasets and in AVIM, which highlighted the complexity and importance of coupling nitrogen with the carbon cycle into land surface models in East Asian monsoon regions.

"The variation by standard deviation and anomaly will be the benchmark to improve the carbon-nitrogen interaction in the future, which can decrease the uncertainty in simulating the carbon-nitrogen flux and improve the land-air interaction at regional scales," said Prof. DAN.

The nitrogen cycle related to carbon flux in the Atmosphere-Vegetation Interaction Model (Image by IAP)