Methane and soil and plant community respiration from wetlands, KejimkujikNational Park, Nova Scotia: Measurements, predictions, and climatic change

A static, dark chamber technique was used weekly from mid-July to mid-Novem ber in 1995 and biweekly from mid-May to late November in 1996, to measure methane (CH4) flux and soil and plant community res ration of CO2 from 36 s ites in two wetlands In Kejimkujik National Park in south-central Nova Scot ia, Canada. Overall mean fluxes of CH4 were 43 mg m(-2) d(-1) in 1995 and 2 0 mg m(-2) d-1 in 1996. Respiration rates were 5.1 g CO2 m(-2) d(-1) in 199 5 and 3.2 g CO2 m(-2) d(-1) in 1996. Fluxes of CH4 and CO2 were related to microtopography and ecological grouping, depth to water table, and air and peat temperatures. Edge and hummock sites showed the lowest CH4 flux and th e highest respiration rate, while pools showed the highest CH4 and lowest r espiration rate. Gas emissions displayed a strong seasonal pattern with hig hest values occurring during the summer (June to August) and with a marked reduction in late fall. Depth to water table and air temperature explained 34 to 43% of the variance in CH4 flux and respiration from the sites over t he 2 years (n = 666 to 824). We developed algorithms relating the daily mea n flux of CH4 and respiration from the wetlands to an aspatial soil moistur e, water table, and temperature model (ForHyM2) applied to the wetland basi ns. We then applied this model to calculated May to October fluxes of CH4 a nd CO2 from 1966 to 1998. We estimated that CH4 fluxes ranged from 2.8 to 7 .4 g m(-2) with a mean of 3.7 g m(-2) and a standard deviation of 1.2 g m(- 2) over the 1966-1998 period. Respiration estimates ranged from 0.60 to 1.1 6 kg CO2 m(-2) with a mean of 0.74 kg CO2 m(-2) and a standard deviation of 0.11 kg CO2 m(-2). Application of a 2xCO(2) General Circulation Model scen ario to temperature and precipitation for this part of eastern Canada resul ted in increases of growing season CH4 emissions from 4.7 to 11.4 g m(-2) a nd respiration from 0.77 to 1.32 kg CO2 m(-2).