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TABLE OF CONTENTSROLE OF BOREAL SOIL'S METHANE CONSUMPTION READERS WRITE JAPAN-CANADA PANEL ON GLOBAL CHANGE AND THE NORTH PACIFIC NEW REPORT IDENTIFIES MAJOR WATER ISSUES FACING CANADA CANADIAN ENVIRONMENTAL ASSESSMENT AGENCY RECEIVES INTERNATIONAL AWARD ATMOSPHERIC CHANGE IN CANADA: ASSESSING THE WHOLE AS WELL AS THE PARTS THE CANADIAN CLIMATE PROGRAM: ACHIEVEMENTS 1990-1994 FINAL WORKSHOP PLANNED FOR THE MACKENZIE BASIN IMPACT STUDY SECOND LOICZ OPEN SCIENCE MEETING FREE-AIR CO2 ENRICHMENT EXPERIMENT IN FOREST CANADIAN CONTRIBUTIONS TO THE INTERNATIONAL HUMAN DIMENSIONS PROGRAMME INTER-AMERICAN INSTITUTE IS UP AND RUNNING FUTURE OF LONG-TERM ECOLOGICAL DATA QUESTIONNAIRE |
The opinions expressed in this newsletter are those of the writers, and do not necessarily represent those of the CGCP.
ROLE OF BOREAL SOIL'S METHANE CONSUMPTION
Nigel Roulet, Department of Geography and the Centre for Climate and Global Change Research, McGill University In the last issue of DELTA (Vol. 5, No. 4; Winter 1994) a few preliminary results of the Boreal Ecosystem Atmosphere Study (BOREAS) were reported. One of the results was incorrectly reported. In the article it was stated that "Although there are significant sources of methane emissions (i.e. fens and beaver ponds) regional emissions appear to be small as a result of uptake by upland soils". The results of BOREAS in fact show the opposite to be true. Because the application of the incorrectly reported results have serious ramifications in the development of national emissions inventories which ultimately affect policy, we feel it is important to attempt to set the record straight. Wetlands in the northern and southern study sites of BOREAS (i.e. bogs, fens and beaver ponds) were found to be large unit area sources of methane to the atmosphere. Tower and enclosure measurements from different groups working in many wetland types indicate methane fluxes in the range observed for other boreal regions. The remote sensing analysis to determine the actual areal extent of wetland in the BOREAS sites is not yet complete, but assuming wetlands comprise between 20 and 25 percent of the landscape (values reported in the National Atlas of Canada), then the wetland source of methane, based on observed fluxes, should be between 2 and 4 g mg CH4 m-2 yr-1 prorated over the entire landscape. This source strength is similar to values reported for other subarctic, boreal, and cool temperate region wetlands in Canada, the United States and Scandinavia. Prior to BOREAS several studies reported methane uptake by upland forest soils. The early results from BOREAS confirm that the uptake of methane by forest soils occurs most of the time, though the flux rates obtained were lower than observed elsewhere. The BOREAS studies also produced some unique observations. First, short, episodic fluxes of methane to the atmosphere from soils that normally consumed methane were noted. The mass of methane released during the short episodes appears to be large relative to the more persistent uptake rates. Second, while uptake is observed beneath the forest canopy, measurements above the canopy at some forest sites indicate some emission of methane. Using the range of uptake rates observed and ignoring the episodic release of methane, and assuming uplands comprise 50 to 60 percent of the landscape, the regional uptake of methane would be less than 0.5 g CH4 m-2 yr-1. Combining the preliminary observations of the regional sources and sinks of methane yields a net regional emission of between 1.5 and 3.5 g CH4 m-2 yr-1 to the atmosphere. BOREAS thus confirms the boreal forest biome as a significant global methane source.
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