[1] Measurements of CH 3 Br exchange at two New Hampshire peatlands (Sallie's Fen and Angie's Bog) indicate that net flux from these ecosystems is the sum of competing production and consumption processes. Net CH 3 Br fluxes were highly variable and ranged from net emission to net uptake between locations within a single peatland. At Sallie's Fen, net CH 3 Br flux exhibited positive correlations with peat temperature and air temperature during all seasons sampled, but these relationships were not observed at Angie's Bog where flux varied according to microtopography. The major CH 3 Br production process at Sallie's Fen appeared dependent on aerobic conditions within the peat, while CH 3 Br production at Angie's Bog was favored by anaerobic conditions. There was evidence of aerobic microbial consumption of CH 3 Br within the peat at both sites. In a vegetation removal experiment conducted at Sallie's Fen with dynamic chambers, all collars exhibited net consumption of CH 3 Br. Net CH 3 Br flux had a negative correlation with surface temperature and a positive correlation with water level in collars with all vegetation clipped consistent with aerobic microbial consumption. Vegetated collars showed positive correlations between net CH 3 Br flux and air temperature. A positive correlation between net CH 3 Br flux and surface temperature was also observed in collars in which all vegetation except Sphagnum spp. were clipped. These correlations are consistent with seasonal relationships observed in 1998, 1999, and 2000 and suggest that plants and/or fungi are possible sources of CH 3 Br in peatlands. Estimates of production and consumption made on two occasions at Sallie's Fen suggest that peatlands have lower rates of CH 3 Br consumption compared to upland ecosystems, but a close balance between production and consumption rates may allow these wetlands to act as either a net source or sink for this gas.
[1] Field enclosure measurements of a temperate forest soil show net uptake of ambient methyl bromide (CH 3 Br), an important trace gas in both tropospheric and stratospheric ozone cycling. The net flux for 1999 was estimated to be À168 ± 72 mg CH 3 Br m À2 (negative indicates loss from the atmosphere). Individual enclosure flux measurements ranged from À4.0 to +3.3 mg CH 3 Br m À2 d À1 . Soil consumption of CH 3 Br was estimated from laboratory soil incubations. Production of CH 3 Br was calculated as the difference between net flux and predicted consumption. Fungi could be responsible for the production of CH 3 Br in this temperate forest soil.
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