Spatial and temporal patterns of CH 4 and N 2 O fluxes in terrestrial ecosystems of North America during 1979-2008: application of a global biogeochemistry model Elevated CO2 Research View project Modeling microbial processes at multiple scales View project Spatial and temporal patterns of CH 4 and N 2 O fluxes in terrestrial ecosystems of North America during 1979-2008: application of a global biogeochemistry model

Abstract

Continental-scale estimations of terrestrial methane (CH 4) and nitrous oxide (N 2 O) 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 biogeochem-ical model, the Dynamic Land Ecosystem Model (DLEM), we quantified simultaneously CH 4 and N 2 O 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 = 10 12 g) of CH 4 , and 1.94 ± 0.1 T g N a −1 of N 2 O were released from terrestrial ecosystems in North Amer-ica. At the country level, both the US and Canada acted as CH 4 sources to the atmosphere, but Mexico mainly oxidized and consumed CH 4 from the atmosphere. Wetlands in North America contributed predominantly to the regional CH 4 source, while all other ecosystems acted as sinks for atmospheric CH 4 , of which forests accounted for 36.8%. Regarding N 2 O 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 N 2 O emission. The inter-annual variations of CH 4 and N 2 O 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 CH 4 flux, both mean annual temperature and annual precipitation were significantly correlated to annual Correspondence to: H. Tian (tianhan@auburn.edu) N 2 O flux. The regional estimates and spatiotemporal patterns of terrestrial ecosystem CH 4 and N 2 O fluxes in North America generated in this study provide useful information for global change research and policy making.