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

A static, dark chamber technique was used weekly from mid-July to mid-November 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 sites in two wetlands In Kejimkujik National Park in south-central Nova Scotia, Canada. Overall mean fluxes of CH4 were 43 mg m(-2) d(-1) in 1995 and 20 mg m(-2) d-1 in 1996. Respiration rates were 5.1 g CO2 m(-2) d(-1) in 1995 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 the highest respiration rate, while pools showed the highest CH4 and lowest respiration rate. Gas emissions displayed a strong seasonal pattern with highest 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 the 2 years (n = 666 to 824). We developed algorithms relating the daily mean flux of CH4 and respiration from the wetlands to an aspatial soil moisture, water table, and temperature model (ForHyM2) applied to the wetland basins. We then applied this model to calculated May to October fluxes of CH4 and 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 1.16 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 scenario to temperature and precipitation for this part of eastern Canada resulted in increases of growing season CH4 emissions from 4.7 to 11.4 g m(-2) and respiration from 0.77 to 1.32 kg CO2 m(-2).