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TitleEighteen year record of forest fire effects on ground thermal regimes and permafrost in the central Mackenzie Valley, NWT, Canada
AuthorSmith, S L; Riseborough, D W; Bonnaventure, P P
SourcePermafrost and Periglacial Processes 2015 p. 1-15,
Alt SeriesEarth Sciences Sector, Contribution Series 20140259
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS95; 96; 105; 106
AreaMackenzie Valley
Lat/Long WENS-130.0000 -124.0000 67.0000 64.0000
Subjectssurficial geology/geomorphology; freezing ground; ground ice; permafrost; thermal regimes; thermal history; Cenozoic; Quaternary
Illustrationslocation maps; tables; plots
ProgramLand-based Infrastructure, Climate Change Geoscience
AbstractGround thermal conditions following a 1994 forest fire, were investigated along a slope adjacent to a pipeline right-of-way in the central Mackenzie Valley. The intensity of the burn and damage to the forest and organic layer were more severe in the upper part of the slope compared to the bottom. Analysis of ground temperature records between 1995 and 2012 indicates that post fire changes to the surface altered the ground temperature regime by allowing more snow to accumulate on the ground as interception by coniferous trees is no longer possible, as well as decreasing albedo and evapotranspiration in summer. Active layers at the affected site effectively doubled between 1995 and 1998 before stabilizing for the remainder of the observation period. Permafrost degradation has likely occurred at the top of the slope where burning was more severe. Towards the end of the study period ground surface temperatures in the upper portion of the slope are now lower then they were post fire (1997) whereas the surface temperatures are currently higher in the lower portion of the slope with no change observed for the Unburnt site. These changes are attributed to the increased reestablishment of aspen willow and tamarack in the upper part of the transect. It appears that permafrost is recovering at all sites, with the exception of the Top of the slope, in response to ongoing vegetation succession which will be important for maintaining cryotic conditions over the long-term as expected climate warming continues in the region.
Summary(Plain Language Summary, not published)
This paper investigates the impact of a forest fire in 1994 on permafrost for a slope adjacent to a pipeline right-of-way in the Mackenzie Valley. Results from an 18 year record of ground temperatures indicate the loss of vegetation and changes in surface characteristics associated with the fire resulted in warming of the ground and increases in summer thaw depth. Where burning was more severe, degradation of permafrost is occurring. These alterations in the surface conditions also increase the sensitivity of permafrost to climate warming so it is unlikely that even with re-establishment of vegetation, that re-fire permafrost conditions will be re-established. These changes in the permafrost conditions resulting from natural disturbances can have implications for landscape stability and infrastructure integrity in adjacent transportation/transmission corridors.