Emissions of nitrous oxide (N2O) from soil surfaces and their historical changes in East Asia: a model-based assessment

This study assessed historical changes in emissions of nitrous oxide (N2O), a potent greenhouse gas and stratospheric ozone-depleting substance, from the soils of East Asia to the atmosphere. A process-based terrestrial ecosystem model (VISIT) was used to simulate the nitrogen cycle and associated N2O emissions as a function of climate, land use, atmospheric deposition, and agricultural inputs from 1901 to 2016. The mean regional N2O emission rate in the 2000s was estimated to be 2.03 Tg N2O year(-1) (1.29 Tg N year(-1) approximately one-third from natural ecosystems and two-thirds from croplands), more than triple the rate in 1901. A sensitivity analysis suggested that the increase of N2O emissions was primarily attributable to the increase of agricultural inputs from fertilizer and manure. The simulated N2O emissions showed a clear seasonal cycle and interannual variability, primarily in response to meteorological conditions and nitrogen inputs. The spatial pattern of the simulated N2O emissions revealed hot spots in agricultural areas of China, South Korea, and Japan. The average N2O emission factor (emission per unit nitrogen input) was estimated to be 1.38%, a value comparable to previous estimates. These biogeochemical modeling results will facilitate identifying ways to mitigate global warming and manage agricultural practices in this region.