Upper picture by Daniel THOMPSON Ph.D. – Forest Fire Research Scientist – Natural Ressources Canada – Wood Buffalo National Park of Canada in North Alberta.
Fires are one among other perturbations affecting bogs. The fire regime went through important changes in the last decades. (Watch the video produced by the Northern Peat Fire Working Group of Guelph and Mc Master universities.)
Fires can be divided into 2 groups: first, fires lighted naturally under specific conditions, second, fires of anthropogenic origins, meaning caused by human activities. If the Grande plée Bleue has gone through fires all along its history till the present period, such events of the second category clearly appeared recently, in connection with the development of the territory. Fires during the pre-contact period (before European colonization) were less frequent then more difficult to be detected into peat samplings, while fires occurred during the contact period and subsequently have happened more often and so are more easily seen when samples are analyzed.
We may suppose, as proposed by Martin Lavoie, that the peat bog has known fires not too severe and rather located in the forest margin nearby. Except for samplings showing scattered charcoals, no layers of abundant ones have been found which could have revealed, by their surface and thickness, fires periods during the laurentian prehistory.
But some evidence of fires that happened during the 19th and the 20th centuries have been documented; they were related to an increase in human activities (draining, fires) creating conditions added to the climatic ones (drought) that were propitious to such events. An event recorded in the 19th century has been reconstituted and described in the book Écologie des tourbières du Québec-Labrador. Probably caused by anthropogenic activities, it left a significant layer of carbonized material.
Yet, the destruction by fire of a forest besides or inside a peatland gives access to the light; such a new condition will help the growth of mosses like the sphagnum. Paradoxically, when a fire destroys trees which are keeping in the shade some areas of the forest, it will help the production of a new biomass. Similarly, the regeneration of a coniferous forest (during a drought) will facilitate more the ignition of a fire than a surface covered with mosses would do.
The example of a fire event located in a vegetal layer corresponding to the 19th century is well described in the book Écologie des tourbières du Québec-Labrador, in page 68, and illustrated on figure 2.19; types of woody vegetation and other plants growing before the fire are shown, also the ones that could grow after because of new conditions, different from the ones prevailing before in the bog.
TEXT: FRANÇOISE DE MONTIGNY-PELLETIER
REVISION: SERGE PAYETTE, professor Dept. Biology, curator of the Herbier (herbarium) Louis-Marie, University Laval, Qc, Canada
François DROUIN – http://www.infodimanche.com/blogues/fdrouin
Daniel THOPMSON – Ph.D. – Chercheur scientifique, chimie de l’environnement – Ressources Naturelles Canada
Peatland carbon cycling in a fire prone landscape, a visual montage published by the Northern Peat Fire Working Group – Science, Management, and Policy, under the direction of Brian W. Benscoter and Merritt R. Turetsky from Guelph University and Dan Thompson and Mike Waddington from Mc Master University.
Écologie des tourbières du Québec-Labrador, under the direction of Serge Payette and Line Rochefort, Presses de l’Université Laval, 2nd ed. 2005.