THE BOG LANDFORMS OF CONTINENTAL WESTERN CANADA IN RELATION TO CLIMATE AND PERMAFROST PATTERNS

In continental western Canada, discontinuous permafrost is almost alwa ys restricted to ombrotrophic peatlands (bogs). Bogs occur mostly as i slands or peninsulas in large, often complex fens or are confined to s mall basins. Permafrost may be present in extensive peat plateaus (or more locally as palsas) and was preceded by a well-developed layer of Sphagnum that served to insulate the peat and lower the pore water tem peratures. Air photo interpretation reveals the occurrence of bogs wit h five types of surface physiography. Concentrated to the south are bo gs without internal patterns that have never had permafrost. Dominatin g the mid-latitudes are bogs with internal lawns and fens with interna l lawns (mostly representing former bogs) that had permafrost lenses i n the past that have recently degraded. Concentrated in the northwest are peat plateaus without internal lawns or distinct collapse scars, b ut with permafrost; dominating in the northernmost area are peat plate aus with extensive permafrost and collapse scars. Relationships are ap parent between the current - 1-degrees-C isotherm and the southern occ urrence of peat plateaus and between the 0-degrees-C isotherm and the southern edge of bogs and fens with internal lawns. We interpret bogs and fens with internal lawns to represent areas where permafrost degra dation is currently occurring at a greater rate than aggradation, seem ingly in response to warmer regional climate, although fire frequency may also be of local importance.