The Areal Pattern of Burned Tree Vegetation in the Subarctic Region of Northwestern Canada

Vegetation and terrain analyses of 1312 air photos spanning the subarctic, low arctic, and portions of the adjacent high boreal region of northwestern Canada permitted geographic characterization of the areal pattern of burned forest and forest-tundra vegetation. In terms of its lower areal extent o...

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Bibliographic Details
Published in:Arctic 1991, Vol.44 (3), p.223-230
Main Authors: Timoney, K. P., Wein, Ross W.
Format: Article
Language:English
Subjects:
Boreal forests
Forest & brush fires
Forest cover
Forest ecology
Forest fires
Forest regeneration
Highlands
Subarctic regions
Trees
Tundras
Vegetation
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Summary:Vegetation and terrain analyses of 1312 air photos spanning the subarctic, low arctic, and portions of the adjacent high boreal region of northwestern Canada permitted geographic characterization of the areal pattern of burned forest and forest-tundra vegetation. In terms of its lower areal extent of burns, and lower frequency of air photos showing burns, the forest-tundra is distinct from both open crown and closed crown forest regions. Burns show a general decrease in areal coverage from the northwest(Mackenzie Riverto Great Bear Lake: 0-50% of the terrain)to the southeast(Great Slave Lake to Hudson Bay: 0-10%). In the northwest, the flat till plains, high cover of continuous mature forest, and scarcity of lakes, coupled with dominance of slowly regenerating white spruce (in the forest-tundra) may help to account for the extensive burned vegetation. In the eastern half of the study region, the northern limit of burns normally does not extend beyondthe line where tree cover equals upland tundra cover. In this eastern sub-region, tree cover decreases rapidly northward within the southern half of the forest-tundra, constraining the areal extent of individual burns. Burns extend about 25-75 km into the forest-tundra, decreasing in areal coverage with distance east of Great Slave Lake. Burn cover in the forest-tundra north of Great Slave Lake generally exceeds that east of Great Slave Lake. Weather patterns and an abundance of lakes may help to account for the lower cover of burns east of Great Slave Lake. Burns north of Great Slave Lake peak in cover in the low Subarctic along a NW-SE axis that lies NE of high fire risk and occurrence zones. Strong correlations were observed between burn cover and upland tundra cover(-r)and between burn cover and the tree: upland tundra cover ratio(+r). /// Des analyses de la végétation et du terrain faites à partir de 1312 clichés aériens pris en survolant le Subarctique, le bas Arctique et des portions de la région boréale extrême adjacente, dans le nord-ouest du Canada, ont permis de définir géographiquement le schéma de la surface recouverte d'une végétation composée de brûlis et de forêt-toundra. Si l'on considère sa superficie moins étendue recouverte de brûlis et le plus petit nombre de clichés aériens révélant des brûlis, la forêt-toundra est différente des régions boisées à voûte ouverte et de celles à voûte fermée. On constate une diminution générale de la superficie des brûlis en allant du nord-ouest(du Mackenzie
ISSN:0004-0843
1923-1245
DOI:10.14430/arctic1542