Seasonal Patterns and Controls on Methane and Carbon Dioxide Fluxes in Forested Swamp Pools

Abstract

We measured seasonal patterns in the fluxes of CH4 and CO2 in a forested wetland in central New York State from 1992 to 1995. The site was a red maple-hemlock swamp with permanent pools (~30cm deep), except when the pools dried during severe drought in 1995. Annual CH4 emissions from the pools to the atmosphere averaged 4.3 (+/- 2.4) mol m-2 during 1993 to 1995 and ranged from 1.9 mol m-2 in 1993 to 6.7 mol m-2 in 1995. CO2 emissions from the pools during 1993 and 1994 were 10.5 and 11.9 mol m-2, accounting for 84.6% and 75.6% of the gaseous carbon export during 1993 and 1994, respectively. A combination of temperature and carbon availability influenced seasonal CH4 and CO2 fluxes more than other environmental factors (temperature, water column depth, O2, CH4, dissolved organic carbon, NH4+, or dissolved inorganic carbon). Based on an observed 12 C threshold temperature, linear regression models explained from 31% to 77% of seasonal gas flux variability. Compared with other forested wetlands, this site produced substantially greater CH4 fluxes, and the CH4 flux accounted for a greater proportion of the total carbon flux from the system.

Keywords:

• Greenhouse Gases;Methane;Wetland