Methane Emissions from Natural Wetlands in the United States: Satellite-Derived Estimation Based on Ecosystem Carbon Cycling

Abstract

Wetlands are an important natural source of methane to the atmosphere. The amounts of methane emitted from inundated ecosystems in the United States can vary greatly from area to area. Seasonal temperature,

Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM

“…Once these competitive interactions have been accounted for, Eq. (1) is solved using a Crank-Nicholson solver (Press et al, 1989) (Appendix A). Two methane balance checks are performed at each timestep to insure that the diffusion solution and the time-varying aggregation over inundated and non-inundated areas strictly conserves methane molecules (except for production minus consumption) and carbon atoms.…”

“…Previous regional and global CH 4 emission models have applied wetland distribution estimates from Matthews and Fung (1987) (e.g., Zhuang et al, 2004;Walter et al, 2001a;Cao et al, 1996), Landsat (Potter et al, 2006), or the IGBP soils database (Wania et al, 2010). However, these static distributions do not allow for prognostic analysis of changes in surface hydrology that may affect CH 4 emissions over the 21st century.…”

“…Grant and Roulet (2002) and Wania et al (2010) described a hierarchy of extant bottom-up ecosystem CH 4 biogeochemical models. Briefly, this hierarchy includes (1) relatively simple regressions of net CH 4 fluxes based on soil properties and climate (Frolking and Crill, 1994;Bellisario et al, 1999;Moore and Roulet, 1993;Christensen et al, 1996;Kaplan, 2002); (2) models that estimate daily fluxes dependent on water chemistry, temperature, and estimates of the C flux moving through the soil system (Potter, 1997); (3) models applied at site, regional, and global scales that include aqueous and gaseous transport, competition between processes affecting CH 4 concentrations, and simple representations of the effects of pH and redox potential (Zhang et al, 2002;Walter et al, 2001a;Wania et al, 2010;Zhuang et al, 2004;Cao et al, 1996;Petrescu et al, 2010;Tian et al, 2010); and (4) models that include details of the various microbial populations that produce and consume CH 4 in the column and their interactions with substrates, pH, and redox potential, in addition to some treatment of the geometry of the rhizosphere and soil horizontal heterogeneity (Grant, 1998(Grant, , 1999Segers et al, 2001;Segers and Leffelaar, 2001a, b). An important further distinction in model characterization is the extent to which they are applicable to regional and global scale simulations, where it is often difficult to specify system properties (e.g., redox potential, pH).…”

Spatial and temporal patterns of CH<sub>4</sub> and N<sub>2</sub>O fluxes in terrestrial ecosystems of North America during 1979–2008: application of a global biogeochemistry model

“…Bridgham et al (2006) estimated that CH 4 emission in North America's wetlands is 9 T g CH 4 a −1 . Using a satellite-derived modeling approach, Potter et al (2006) estimated that the CH 4 emission from the natural wetlands in the conterminous US is 5.5 T g CH 4 a −1 . Several studies also reported the fluxes of N 2 O in terrestrial ecosystems at global and regional scales using empirical approaches .…”

Observation of CH4 and other Non-CO2 Green House Gas Emissions from California

“…CH 4 emissions from crop agriculture were assumed to follow emissions from the DNDC model for an average climate year with high irrigation as described by Salas et al (2006). CH 4 emissions from wetlands in California were assumed to follow the NASA-CASA estimates from Potter et al (2006). Although some of these sources are expected to vary on a seasonal basis, they do not incorporate temporal variation in current study, which may cause the a priori emissions to be slightly overestimated or underestimated.…”