Interannual, seasonal, and retrospective analysis of the methane and carbon dioxide budgets of a temperate peatland

Abstract

Three years (2009-2011) of near-continuous methane (CH₄) and carbon dioxide (CO₂) fluxes were measured with the eddy covariance (EC) technique at a temperate peatland located within the Marcell Experimental Forest, in northern Minnesota, USA. The peatland was a net source of CH₄ and a net sink of CO₂ in each year with annual carbon budgets of -26.8 (±18.7), -15.5 (±14.8), and -14.6 (±21.5) g Cm^-2 yr^-1 for 2009-2011, respectively. Differences in the seasonal hydrometeorological conditions among the three study years were most pronounced during 2011, which was considerably warmer (+1.3°C) and wetter (+40mm) than the 30 year average. The annual CH₄ budget was +11.8 (±3.1), +12.2 (±3.0), and +24.9 (±5.6) g Cm^-2 yr^-1 for the respective years and accounted for 23%-39% of the annual carbon budget. The larger CH₄ emission in 2011 is attributed to significant warming of the peat column coupled with a high water table position throughout the entire growing season. Historical (1991-2011) CH₄ emissions were estimated based on long-term hydrometeorological records and functional relationships derived from our 3 year field study. The predicted historical annual CH₄ budget ranged from +7.8 to +15.2 (±2.7) g CH₄-Cm^-2 yr^-1. Recent (2007-2011) increases in temperature, precipitation, and rising water table at this site suggest that CH₄ emissions have been increasing, but were generally greater from 1991 to 1999 when average soil temperature and precipitation were higher than in recent years. The global warming potential (considering CO₂ and CH₄) for this peatland was calculated based on a 100 year time horizon. In all three study years, the peatland had a net positive radiative forcing on climate and was greatest (+187 g Cm^-2) in 2011. The interannual variability in CH₄ exchange at this site suggests high sensitivity to variations in hydrometeorological conditions.

Citation

Olson, D.M.; Griffis, T.J.; Noormets, A.; Kolka, R.; Chen, J. 2013. Interannual, seasonal, and retrospective analysis of the methane and carbon dioxide budgets of a temperate peatland. Journal of Geophysical Research: Biogeosciences. 118(1): 226-238.