气候变化领域集成服务门户

A process-based dynamic ecosystem model of TRIPLEX-GHG was used to estimate the spatial and temporal patterns of N2O fluxes from global forest and grassland ecosystems under the effects of global warming and elevated CO2 concentrations. From 1992 to 2015, the estimated average N2O emissions from forests and grasslands were 3.62 +/- 0.16 Tg N yr(-1) and 1.40 +/- 0.03 Tg N yr(-1), respectively. Tropical regions made large contributions (83.9% for forests and 74% for grasslands) to the total N2O budgets, which were due to the larger N2O flux values and large natural forest and grassland areas. The regional variations in N2O emissions mainly resulted from the differences in the spatial distributions of climate characteristics, especially the precipitation patterns. In addition, anomalous years when N2O emissions were relatively low/high were mainly due to the changes in climate patterns, which may have been induced by El Nino/La Nina events with different strengths and frequencies. Soil N2O emissions from forests showed a positive effect on the atmospheric N2O concentrations during June to November (R-2 : 0.14(similar to)0.28), while those from grasslands showed a positive effect during the growing seasons (R-2 : 0.17(similar to)0.28). Although natural N2O sources (forests and grasslands in this study) showed slightly increasing trends, with 9.9 Gg N increment per year for forests and 2.1 Gg N increment per year for grasslands, they were not the main contributors to the elevated N2O concentrations.