A COMPARISON OF DYNAMIC AND STATIC CHAMBERS FOR METHANE EMISSION MEASUREMENTS FROM SUB-ARCTIC FENS

Methane emissions measured at three subactic fen sites by dynamic and static chambers were compared; in the dynamic chambers, the air was circulated at a wind speed of 1.9 m s-1. Emissions ranged from 7 to 214 mg CH4 m-2 d-1 and measurements from the two types of chamber were strongly correlated (r2 = 0.72), with no overall difference between the means (paired t-test, p = 0.34) and with only 4 of the 14 comparisons showing statistically different means (t-test, p < 0.25). The overall ratio of dynamic: static chamber fluxes was 1.24, but was highest (1.68) at the wettest, central site and lowest (0.74) at the driest, edge site. The coefficients of variation of chamber flux measurements at each site ranged from 0.13 to 1.77, with an overall average of 0.53; sampling with over 30 static chambers revealed approximately normal distributions at the edge and middle sites and a positively skewed distribution at the central site. Within both static and dynamic chambers, methane concentrations increased linearly through 24 h. These inexpensive, protable static chambers can be used to replicate methane emission measurements within a wide range of wetland sites.