Spatial and temporal patterns of CH₄ and N₂O fluxes in terrestrial ecosystems of North America during 1979-2008: Application of a global biogeochemistry model

Continental-scale estimations of terrestrial methane (CH₄) and nitrous oxide (N₂O) fluxes over a long time period are crucial to accurately assess the global balance of greenhouse gases and enhance our understanding and prediction of global climate change and terrestrial ecosystem feedbacks. Using a process-based global biogeochemical model, the Dynamic Land Ecosystem Model (DLEM), we quantified simultaneously CH₄ and N ₂O fluxes in North America's terrestrial ecosystems from 1979 to 2008. During the past 30 years, approximately 14.69 ± 1.64 T g C a ^-1 (1 T g Combining double low line 10¹² g) of CH ₄, and 1.94 ± 0.1 T g N a^-1 of N₂O were released from terrestrial ecosystems in North America. At the country level, both the US and Canada acted as CH₄ sources to the atmosphere, but Mexico mainly oxidized and consumed CH₄ from the atmosphere. Wetlands in North America contributed predominantly to the regional CH₄ source, while all other ecosystems acted as sinks for atmospheric CH ₄, of which forests accounted for 36.8%. Regarding N₂O emission in North America, the US, Canada, and Mexico contributed 56.19%, 18.23%, and 25.58%, respectively, to the continental source over the past 30 years. Forests and croplands were the two ecosystems that contributed most to continental N₂O emission. The inter-annual variations of CH ₄ and N₂O fluxes in North America were mainly attributed to year-to-year climatic variability. While only annual precipitation was found to have a significant effect on annual CH₄ flux, both mean annual temperature and annual precipitation were significantly correlated to annual N₂O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH₄ and N₂O fluxes in North America generated in this study provide useful information for global change research and policy making.