MEASUREMENTS OF CH4 AND N2O FLUXES AT THE LANDSCAPE SCALE USING MICROMETEOROLOGICAL METHODS

Flux gradient, eddy covariance and relaxed eddy accumulation methods w ere applied to measure CH4 and N2O emissions from peatlands and arable land respectively. Measurements of N2O emission by eddy covariance us ing tunable diode laser spectroscopy provided fluxes ranging from 2 to 60 mu mol N2O m(-2) h(-1) with a mean value of 22 mu mol N2O m(-2) h( -1) from 320 h of continuous measurements. Fluxes of CH4 measured abov e peatland in Caithness (U.K.) during May and June 1993 by eddy covari ance and relaxed eddy accumulation methods were in the range 70 to 120 mu mol CH4 m(-2) h(-1) with means of 14.7 mu.mol CH4 m(-2) h(-1) and 22.7 mu mol CH4 m(-2) h(-1) respectively. Emissions of CH4 from peatla nd changed with mater table depth and soil temperature; increasing fro m 25 mu mol CH4 m(-2) h(-1) at 5% pool area to 50 mu mol CH4 m(-2) h(- 1) with 30% within the flux footprint occupied by pools. A temperature response of 4.9 mu mol CH4 m(-2) h(-1) degrees C-1 in the range 6-12 degrees C was also observed. The close similarity in average CH4 emiss ion fluxes reported for wetlands in Caithness, Hudson Bay and Alaska i n the range 11 to 40 mu mol CH4 m(-2) h(-1) suggests that earlier esti mates of CH4 emission from high latitude wetlands were too large or th at the area of high latitudes contributing to CH4 emission has been se riously underestimated.