Methyl bromide and methyl chloride fluxes from temperate forest litter

Abstract

Methyl halide fluxes were measured from fine (nonwoody) litter samples in a temperate deciduous forest site in Scotland on 16 occasions over more than a year and from a coniferous forest site. The resulting mean (+/-1 sd) CH3Br and CH3Cl fluxes were 4.1 +/- 3.7 ng kg-1 h-1 and 0.98 +/- 0.62 µg kg-1 h-1, respectively, for dry mass leaf litter and 5.7 +/- 6.3 ng kg-1 h-1 and 0.47 +/- 0.14 µg kg-1 h-1 for dry mass needle litter. Temporal variations of net fluxes from leaf litter were significantly greater than spatial variations suggesting seasonality in the fluxes. The mean CH3Cl/CH3Br mass ratio of fluxes was ~200, an order of magnitude larger than the ratio of their estimated global turnovers. Temperate forest litter may be a moderate net source of CH3Cl globally but a negligible source of CH3Br. These statements refer to the nonwoody litter component only.