Alain Leduc, Damien Rius, Sylvie Gauthier, Martin-Philippe Girardin, Han Chen, Hugo Asselin, Igor Drobyshev, Pierre Grondin, Martin Simard, Christelle Hely-Alleaume, Adam Ali, Olivier Blarquez, Alexander Kryshen
Bi-Tchoko Vincent Evrard Kouadio, Marianne Vogel, Nina Ryzhkova, Andy Hennebelle, Augustin Feussom
L’aménagement écosystémique vise à recréer des conditions semblables à celles issues des perturbations naturelles. Il est donc essentiel de pouvoir reconstruire les régimes de perturbations et leurs influences sur la mosaïque forestière pour pouvoir fixer des objectifs crédibles.
Reconstruire les régimes de feux et la dynamique naturelle des peuplements dans le but de les utiliser comme objectifs en aménagement écosystémique.
Comme les régimes de perturbations ont été modifiés par l’action humaine et les fluctuations climatiques, il est nécessaire d’utiliser des approches dendroécologiques (dernier 300 ans) ou paléoécologiques (période Holocène) pour pouvoir bien caractériser les variations naturelles.
Connaissances de base permettant de fixer des objectifs quant à la mise en place d’un aménagement écosystémique.
Forêt boréale de l'est de l'Amérique du nord surtout mais région circumboréale en général.
Martin-Philippe Girardin, Jeanne Portier, Cécile Remy, Adam Ali, Jordan Paillard, Olivier Blarquez, Hugo Asselin, Sylvie Gauthier, Yves Bergeron, Pierre Grondin. Coherent signature of warming-induced extreme sub-continental boreal wildfire activity 4,800 and 1,100 years BP. 2019. Environmental Research Letters 14(12):124042
DOI : 10.1088/1748-9326/ab59c9
Climate changes are expected to progressively increase extreme wildfire frequency in forests. Finding past analogs for periods of extreme biomass burning would provide valuable insights regarding what the effects of warming might be for tree species distribution, ecosystem integrity, atmospheric greenhouse gas balance, and human safety. Here, we used a network of 42 lake-sediment charcoal records across a ~2000 km transect in eastern boreal North America to infer widespread periods of wildfire activity in association with past climate conditions. The reconstructed fluctuations in biomass burning are broadly consistent with variations in ethane concentration in Greenland polar ice cores. Biomass burning fluctuations also significantly co-varied with Greenland temperatures estimated from ice cores, at least for the past 6000 years. Our retrospective analysis of past fire activity allowed us to identify two fire periods centered around 4800 and 1100 BP, coinciding with large-scale warming in northern latitudes and having respectively affected an estimated ~71% and ~57% of the study area. These two periods co-occurred with widespread decreases in mean fire-return intervals. The two periods are likely the best analogs for what could be anticipated in terms of impacts of fire on ecosystem services provided by these forests in coming decades.
Yves Bergeron, Jeanne Portier, Sylvie Gauthier. Spatial distribution of mean fire size and occurrence in
eastern Canada: influence of climate, physical environment
and lightning strike density. 2019. International Journal of Wildland Fire 28:927-940
DOI : 10.1071/WF18220
In Canada, recent catastrophic wildfire events raised concern from governments and communities. As climate
change is expected to increase fire activity in boreal forests, the need for a better understanding of fire regimes is becoming
urgent. This study addresses the 1972–2015 spatial distributions of fire cycles, mean fire size (FireSz) and mean fire
occurrence (mean annual number of fires per 100 000 ha, FireOcc) in eastern Canada. The objectives were to determine
(1) the spatial variability of fire-regime attributes, (2) the capacity of FireSz and FireOcc to distinguish homogeneous fire
zones and (3) the environmental factors driving FireSz and FireOcc, with some emphasis on lightning strikes. Fire cycles,
FireSz and FireOcc greatly varied throughout the study area. Even within homogeneous fire zones, FireSz and FireOcc
were highly variable. FireSz was controlled by moisture content in deep layers of the soil and by surficial deposits, whereas
FireOcc was controlled by moisture content in top layers of the soil and by relief. The lack of a relationship between
FireOcc and lightning-strike density suggested that the limiting effect of lightning-strike density on FireOcc could be
operating only under certain circumstances, when interacting with other environmental factors.
Dinesh Babu Irulappa Pillai Vijayakumar, Hakim Ouzennou, Sylvie Gauthier, Yves Bergeron, Alain Leduc, Frédérick Raulier . Projections of future forest age class structure under the influence of fire and harvesting: implications for forest management in the boreal forest of eastern Canada. 2017. Forestry 90(4):485-495
DOI : 10.1093/forestry/cpx022
In northeastern Canadian boreal forests, a coarse-filter approach was adopted to provide sustainable ecosystem services in order to maintain a balance between biodiversity, ecosystem function and timber production. An old forest (>100 years) maintenance target was established considering the range of historical variability in the proportion of this forest stage. However, the estimation of the harvesting rate that maintains the target level in old forests did not consider explicitly the impact of current and future, i.e. possibly higher, fire frequency. In this context, we compared historical, current, and future age structures according to recorded or projected fire activity and the current level of harvesting in western Quebec's boreal forest. Results show that under the current rates of harvesting and fire, the proportion of old forests could reach a minimum level rarely seen in the natural landscape in the past. The situation could become even more critical with the projected increase in fire activity under climate change. Numerous forest and fire management solutions exist, such as increasing rotation length, implementing a diversified silviculture, using a fire-smart approach or reaching a better balance between intensive management and conservation. We advocate their rapid implementation to reverse the projected decrease in the proportion of old forests.
Andy Hennebelle, Julie C. Aleman, Yves Bergeron, Daniel Borcard, Pierre Grondin, Olivier Blarquez, Adam Ali. Using paleoecology to improve reference conditions for ecosystem-based
management in western spruce-moss subdomain of Québec. 2018. For. Ecol. Manage. 430:157-165
DOI : 10.1016/j.foreco.2018.08.007
Ecosystem based management in Québec is framed by reference conditions defining percentage of old-growth forest (>100-years-old) and forest composition characterizing pre-industrial forest landscapes. In the western spruce-moss bioclimatic subdomain (154?184?km2) a fire cycle estimated at 150?years was used to target that 49% of the landscape has to be composed of old-growth forest. Yet, this target was developed using past (19th–20th C.) climate and vegetation data and assume that environment and ecosystem processes are homogeneous for the entire western spruce-moss bioclimatic subdomain. The wide spatial and narrow temporal windows limit the application of reference conditions under ongoing climate change.
Our aim was to classify current vegetation heterogeneity of the western spruce-moss subdomain into homogeneous zones and to study the long-term history of fire and vegetation within these zones. This approach will help to refine forest management targets that are based upon short-term records by providing a long-term perspective that is needed for the forests to be managed within their natural range of variability. Modern forest inventories data were used along with climate, physical variables, and natural and human disturbances to study the current vegetation-environment interactions among the western spruce-moss subdomain. We also used 18 published sedimentary pollen and charcoal series to reconstruct Holocene vegetation and Fire Return Intervals (FRI).
Contemporary data revealed 4 zones with homogeneous interactions between vegetation and environment. Pollen analysis revealed three long-term vegetation paths: early successional species dominance, late to early species transition and late successional species dominance. These suggest that modern forest composition results from Holocene trajectories occurring within each zone. Holocene mean FRI (mFRI) ranged from 222 to 258 years across the subdomain, resulting in old-growth forests ranging between 64% and 68%, depending upon the zone.
Paleoecological and contemporary results support that to make forest management more sustainable, current landscape heterogeneity that arises from millennial forest composition trajectories and fire cycle dynamics should be taken into account by down-scaling the previously established reference conditions.
Pierre Grondin, Véronique Poirier, Sylvie Gauthier, Patrice Tardif, Yan Boucher, Yves Bergeron. Have some landscapes in the eastern
Canadian boreal forest moved beyond their
natural range of variability? 2018. Forest Ecosystems 5(1):30
DOI : 10.1186/s40663-018-0148-9
In the context of ecosystem management, the present study aims to compare the natural and the present-day forested landscapes of a large territory in Quebec (Canada). Using contemporary and long-term fire cycles, each natural forest landscape is defined according to the variability of its structure and composition, and compared to the present-day landscape. This analysis was conducted to address the question of whether human activities have moved these ecosystems outside the range of natural landscape variability.
L’analyse des données récoltées dans les territoires du Nord-Ouest est en cours. Une synthèse des travaux sur les lacs est disponibles (Girardin et al. 2019) et une synthèse des études dendrochronologiques est en voie de réalisation.
CRSNG, MITACS, SÉPAQ (Parc Aiguebelle)
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