Forest fires in Canadian permafrost region : the combined effects of fire and permafrost dynamics on soil organic matter quality

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Aaltonen , H , Koster , K , Koster , E , Berninger , F , Zhou , X , Karhu , K , Biasi , C , Bruckman , V , Palviainen , M & Pumpanen , J 2019 , ' Forest fires in Canadian permafrost region : the combined effects of fire and permafrost dynamics on soil organic matter quality ' , Biogeochemistry , vol. 143 , no. 2 , pp. 257-274 . https://doi.org/10.1007/s10533-019-00560-x

Title: Forest fires in Canadian permafrost region : the combined effects of fire and permafrost dynamics on soil organic matter quality
Author: Aaltonen, Heidi; Koster, Kajar; Koster, Egle; Berninger, Frank; Zhou, Xuan; Karhu, Kristiina; Biasi, Christina; Bruckman, Viktor; Palviainen, Marjo; Pumpanen, Jukka
Contributor: University of Helsinki, Forest Soil Science and Biogeochemistry
University of Helsinki, Department of Forest Sciences
University of Helsinki, Forest Soil Science and Biogeochemistry
University of Helsinki, Forest Ecology and Management
University of Helsinki, Department of Forest Sciences
University of Helsinki, Department of Forest Sciences
University of Helsinki, Department of Forest Sciences
Date: 2019-03
Language: eng
Number of pages: 18
Belongs to series: Biogeochemistry
ISSN: 0168-2563
URI: http://hdl.handle.net/10138/301144
Abstract: Wildfires burn approximately 1% of boreal forest yearly, being one of the most significant factors affecting soil organic matter (SOM) pools. Boreal forests are largely situated in the permafrost zone, which contains half of global soil carbon (C). Wildfires advance thawing of permafrost by burning the insulating organic layer and decreasing surface albedo, thus increasing soil temperatures. Fires also affect SOM quality through chemical and physical changes, such as the formation of resistant C compounds. The long-term post-fire effects on SOM quality, degradability and isotopic composition are not well known in permafrost forests. We studied the effect of forest fires on the proportional sizes of SOM pools with chemical fractionation (extracting with water, ethanol and acid) of soil samples (5, 30 and 50cm depths) collected from a fire chronosequence in the upland mineral soils of the Canadian permafrost zone. We also determined the C-13 and N-15 isotopic composition of soil after fire. In the topsoil horizon (5cm) recent fire areas contained a smaller fraction of labile SOM and were slightly more enriched with N-15 and C-13 than older fire areas. The SOM fraction ratios reverted towards pre-fire status with succession. Changes in SOM were less apparent deeper in the soil. Best predictors for the size of recalcitrant SOM fraction were active layer depth, vegetation biomass and soil C/N ratio, whereas microbial biomass was best predicted by the size of the recalcitrant SOM fraction. Results indicated that SOM in upland mineral soils at the permafrost surface could be mainly recalcitrant and its decomposition not particularly sensitive to changes resulting from fire.
Subject: Chemical fractionation
Microbial biomass
Wildfire
NATURAL N-15 ABUNDANCE
CARBON-ISOTOPE RATIOS
TEMPERATURE SENSITIVITY
TUNDRA ECOSYSTEMS
MYCORRHIZAL FUNGI
MINERAL SOILS
DECOMPOSITION
NITROGEN
C-13
NORTHERN
4112 Forestry
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