HR: 1340h
AN: B43B-0161    [Abstracts]
TI: Episodic spring release of CH4 through complete snow cover at a boreal mire as measured with micro-meteorological gradient technique
AU: * Klemedtsson, L
EM: leif.klemedtsson@botany.gu.se
AF: Botanical Institute, G”teborg University, P.O. Box 461, G”teborg, SE 405 30 Sweden
AU: Nilsson, M
EM: Mats.B.Nilsson@sek.slu.se
AF: Department of Forest Ecology, Swedish University of Agricultural Sciences, Ume†, SE-901 83 Sweden
AU: Wagner-Riddler, C
EM: cwagnerr@uoguelph.ca
AF: Department of Land Resource Science, University of Guelph, Guelph, N1G 2W1 Canada
AU: Weslien, P
EM: per.weslien@botany.gu.se
AF: Botanical Institute, G”teborg University, P.O. Box 461, G”teborg, SE 405 30 Sweden
AB: Methane flux was monitored by the micrometerological gradient method and a tunable diod laser at a boreal mire in northern Sweden from late thaw to late spring (April 17th to May 24ht). The part of the mire monitored is dominated by oligotrophic low sedge lawns, with a limited area of carpets with pools and also one sector dominated by ridges and flarks. The snowmelt period was characterized by high episodic release (hourly values, 5-15 mg CH4 h-1 m-2) with daily averages up to 5 mg CH4 h-1 m-2. High episodic release during snowmelt occurred from lawn areas with ten centimeter or more snow on top of the standing water. At the pool area the snow cover was thin with standing water close to the snow surface, the hourly methane flux rates from this area being <2 mg CH4 h-1 m-2. After snowmelt, a period of about thirty days followed without any episodic release and daily averages normally between 0.6 - <2 mg CH4 h-1 m-2. From May 20 to May 24 the daily average flux increased from <2 mg CH4 h-1 m-2 to 8 mg CH4 h-1 m-2, with hourly values up to 13 mg CH4 h-1 m-2. Not only the flux rates changed during the five week period monitored, but also the diurnal methane flux pattern varied considerably both with time period but also due to the particular mire area monitored by the mast. During snowmelt, the hourly flux rate peaked at night between 20 and 02 hours. During the following periods distinct diurnal variation in methane flux rates occurred from areas dominated by vascular plants while the methane flux from areas with less dense vascular plant vegetation was lower and constant during the day. The diurnal amplitude increased from 1.5 mg CH4 h-1 m-2 (1 mg CH4 h-1 m-2 at night and 2.5 mg CH4 h-1 m-2 during the day) at late April to 7 mg CH4 h-1 m-2 (2 mg CH4 h-1 m-2 at night and 9 mg CH4 h-1 m-2 during the day) in late May.
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting