Forest fires in the northern boreal forests of Canada – soil carbon turnover on permafrost and non-permafrost areas.

Theme 1. Environmental protection
Session Name 1.10 Biogeochemical cycles in Arctic forests
Datetime Sep 07, 2018 02:00 PM - 02:15 PM (UTC +3)
Location Room 14
Presentation Type Oral
Presenter Kajar Köster
Author(s) Kajar Köster (University of Helsinki, Finland), Frank Berninger (University of Helsinki, Finland), Heidi Aaltonen (University of Helsinki, Finland), Egle Köster (University of Helsinki, Finland), Jukka Pumpanen (University of Eastern Finland, Finland)
Abstract text

Boreal forests, which cover 15% of the Earth, are a crucial part of the climate system as they contain 60% of the carbon (C) bound in global forest biomes and approximately 12–13% of the organic C stocks in the world’s soils. The turnover time of that C can range from several decades to millennia. Fire is the most important natural disturbance in the boreal forest, strongly influencing boreal forest structure and functions.


In this study, we characterize the post-fire C dynamics (CO2 efflux, soil C content, and soil C turnover times) along a fire chronosequences in northern boreal forests of north-western Canada - along the Klondike Highway (non-permafrost areas) and Dempster Highway (permafrost areas), in Northwest Territories and Yukon, Canada.


The fire chronosequence in permafrost areas consisted areas with last forest fire in years 2012, 1990 and 1969, and fire more than 100 years ago. The fire chronosequence in non-permafrost areas consisted areas with last forest fire in years 2013, 1969 and 1950, and fire more than 100 years ago.


The total soil C contents in the first 30 cm of the topsoil were lowest in newly burned areas and total soil C content was higher in areas with permafrost. Same trends were observed when soil CO2 effluxes (both field measurements and incubation study results) were analyzed. The areas with permafrost were shoving about 1.5x higher values than non-permafrost areas. Thus, all in all soil C turnover time had no significant difference when permafrost and non-permafrost areas were compared.

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