Project

Modelling and mapping post-fire black spruce regeneration in a context of global change in eastern Canada

Goal: This study aims to develop a predictive tool for black spruce post-fire regeneration using stand disturbance history, and climate/site conditions. First, we want to developed a theoretical model that combined spatial variables (stand/site/climate conditions) commonly used by forest managers in eastern Canada, a fire severity index (“differenced normalized burn ratio”, or dNBR) and variables collected by in situ sampling (residual organic matter, tree age, twig severity index). Second, we will developed a spatially explicit model to predict post-fire regeneration using only spatial variables readily available in existing datasets. Our model will allow to incorporate climatic scenarios and will permit to evaluate post-fire resilience and productivity of boreal forest in a context of global change.

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Project log

Osvaldo Valeria
added a research item
Forest fires are a key driver of boreal landscape dynamics and are expected to increase with climate change in the coming decades. A profound understanding of the effects of fire upon boreal forest dynamics is thus critically needed for our ability to manage these ecosystems and conserve their services. In the present study, we investigate the long-term post-fire forest dynamics in the southern boreal forests of western Quebec using historical aerial photographs from the 1930s, alongside with modern aerial photographs from the 1990s. We quantify the changes in forest cover classes (i.e., conifers, mixed and broadleaved) for 16 study sites that were burned between 1940 and 1970. We then analyzed how interactions between pre-fire forest composition, site characteristics and a fire severity weather index (FSWI) affected the probability of changes in forest cover. In the 1930s, half of the cover of sampled sites were coniferous while the other half were broadleaved or mixed. Between the 1930s and the 1990s, 41% of the areas maintained their initial cover while 59% changed. The lowest probability of changes was found with initial coniferous cover and well drained till deposits. Moreover, an important proportion of 1930s broadleaved/mixed cover transitioned to conifers in the 1990s, which was mainly associated with high FSWI and well-drained deposits. Overall, our results highlight a relatively high resistance and resilience of southern boreal coniferous forests to fire, which suggest that future increase in fire frequency may not necessarily result in a drastic loss of conifers.
Osvaldo Valeria
added a research item
Abstract In this study, we used data from multiple sensors onboard NASA Aqua satellite to conduct a 10‐year (2002–2011) remote sensing of microwave emissivity difference vegetation index (EDVI) over China. We investigated the spatial and temporal variations of EDVI in tropical and subtropical evergreen forest, deciduous forest, rice and wheat farmlands, grassland, and montane vegetation regions. The average of China's EDVI is positive in dense vegetation regions and negative in sparse vegetation regions, depending on the proportion of bare soil and open water. In all selected studying regions, the seasonal variation of EDVI follows the trend of vegetation phenology, even in regions with large proportion of open water. EDVI is positively correlated to the greenness of vegetation (normalized difference vegetation index [NDVI]) with certain phase difference in their seasonal cycle. In autumn, EDVI begins to decline earlier and faster than NDVI. In tropical rainforest, EDVI also starts to increase earlier than NDVI in spring. The large‐scale spatial distribution of EDVI under clear sky and cloudy sky is similar. In montane vegetation regions, EDVI under heavy clouds (90% fraction) conditions is significantly greater than that under clear sky (10% fraction), indicating a possible cloud induced enhancement of vegetation water content. In forests and croplands in the plains, such effect is not remarkable.
Osvaldo Valeria
added 2 research items
Le projet visait à développer un outil permettant d’améliorer le processus de prises de décisions quant à la remise en production du territoire forestier suite à un feu de forêt. Cet outil prend la forme d’une application dans le logiciel ArcGIS et indique le potentiel de régénération d’une superficie par rapport à différents critères écologiques ainsi qu’à la sévérité du feu. La clé décisionnelle sous-jacente à l’outil a été développée en se basant sur la littérature scientifique disponible et sur les connaissances acquises par les travaux de recherche menés par la Chaire industrielle CRSNG-UQAT-UQAM en aménagement forestier durable (Chaire AFD) et le Service canadien des forêts (SCF) sur les facteurs affectant la capacité de régénération des espèces d’arbres boréales. L’outil spatial d’aide à la décision élaboré permet une meilleure visualisation de la productivité futures des superficies brulées ainsi qu’une meilleure planification de leur remise en production, le tout permetant de faciliter le travail des aménagistes et des décideurs du milieu forestier.
In the managed boreal forest, harvesting has become a disturbance as important as fire. To assess whether forest recovery following both types of disturbance is similar, we compared post-disturbance revegetation rates of forests in 22 fire events and 14 harvested agglomerations (harvested areas over 5-10 years in the same vicinity) in the western boreal forest of Quebec. Pre-disturbance conditions were first compared in terms of vegetation cover types and surficial deposit types using an ordination technique. Post-disturbance changes over 30 years in land cover types were characterized by vectors of succession in an ordination. Four post-disturbance stages were identified from the 48 land thematic classes in the Landsat images: "S0" stand initiation phase; "S1" early regeneration phase; "S2" stem exclusion phase; and "S3" the coniferous forest. Analyses suggest that fire occurs in both productive and unproductive forests, which is not the case for harvesting. Revegetation rates (i.e., rapidity with which forest cover is re-established) appeared to be more advanced in harvested agglomerations when compared with entire fire events. However, when considering only the productive forest fraction of each fire, the revegetation rates are comparable between the fire events and the harvested agglomerations. The S0 is practically absent from harvested agglomerations, which is not the case in the fire events. The difference in revegetation rates between the two disturbance types could therefore be attributed mostly to the fact that fire also occurs in unproductive forest, a factor that has to be taken into account in such comparisons.
Yan Boucher
added a research item
La récurrence des feux ainsi que la productivité relativement faible des forêts situées dans la portion nordique de la forêt boréale conditionnent la capacité d'y produire du bois de manière durable. Notre connaissance des régimes de feu nous montre qu'il est hautement probable que des quantités significatives de bois brûleront au cours des prochaines décennies. De plus, lorsque le feu détruit des peuplements jeunes, pas encore bien pourvus d'arbres semenciers, des accidents de régénération se produiront à des endroits où l'accès sera parfois difficile. Il est donc nécessaire de prévoir que la remise en production des superficies brûlées mobilisera parfois une part importante des futurs budgets sylvicoles si l'on veut conserver la même base de territoire productif. Or, parce que le risque de feu demeure élevé, une bonne partie de ces plantations sont susceptibles de ne pas atteindre leur âge de maturité. Que faire? En connaissant ces risques, il est possible d'envisager des options qui permettront de faire bon usage des budgets sylvicoles; par exemple, en évitant les zones à très haut risque, en modulant le choix des essences à planter et en élaborant des stratégies sylvicoles qui minimisent les investissements à risque.
Yan Boucher
added a research item
Satellite-derived spectral indices such as the relativized burn ratio (RBR) allow fire severity maps to be produced in a relatively straightforward manner across multiple fires and broad spatial extents. These indices often have strong relationships with field-based measurements of fire severity, thereby justifying their widespread use in management and science. However, satellite-derived spectral indices have been criticized because their non-standardized units render them difficult to interpret relative to on-the-ground fire effects. In this study, we built a Random Forest model describing a field-based measure of fire severity, the composite burn index (CBI), as a function of multiple spectral indices, a variable representing spatial variability in climate, and latitude. CBI data primarily representing forested vegetation from 263 fires (8075 plots) across the United States and Canada were used to build the model. Overall, the model performed well, with a cross-validated R2 of 0.72, though there was spatial variability in model performance. The model we produced allows for the direct mapping of CBI, which is more interpretable compared to spectral indices. Moreover, because the model and all spectral explanatory variables were produced in Google Earth Engine, predicting and mapping of CBI can realistically be undertaken on hundreds to thousands of fires. We provide all necessary code to execute the model and produce maps of CBI in Earth Engine. This study and its products will be extremely useful to managers and scientists in North America who wish to map fire effects over large landscapes or regions.
Yan Boucher
added a research item
Avis technique portant sur les peuplements à cibler comme forêt résiduelle en fonction de la densité de régénération après feu dans la région Nord du Québec dans un contexte de plan de récupération des bois brûlés.
Yan Boucher
added a research item
Dans un contexte de changements globaux, les évènements naturels extrêmes tel que les feux de forêt augmenteront et s'intensifieront (en fréquence et en sévérité), modifiant ainsi la composition et la structure de la forêt boréale canadienne. Ces changements écologiques drastiques risquent d'avoir des impacts majeurs sur la productivité de la forêt boréale. Le projet présenté fait partie d'un effort national pour évaluer et caractériser la sévérité des feux dans un contexte de modélisation de la régénération de l'épinette noire et pour l'aide à la décision dans un contexte de récupération des bois brûlés.
Yan Boucher
added an update
We recently obtained a NSERC collaborative research and development (CRD) grants (540k$) in collaboration with Tembec-Rayonier, Resolute forest products, Barrette-Chapais Ltd, Rebec inc. Rival Solutions, UQAT, USherbrooke, UMontréal and the Government of Québec. This large-scale project will allow to evaluate burn severity and his impact on black spruce post-fire regeneration in a context of global change. We also developing new techniques using Lidar to optimize road network. We have some opportunities for graduates students or postdocs.
 
Yan Boucher
added a research item
In a context of global climate change, natural extreme events such as forest fires will increase and intensify (in frequency and severity) while modifying the composition and structure of the Canadian boreal forest. Such drastic changes will have major impacts on the boreal forest productivity. The work presented here is within the framework of a national effort to monitor and characterize fire severity in order to simulate black spruce regeneration and to assist rapid and efficient salvage logging. This study aims to characterize fire severity at three different scales : in situ, drone-derived very high resolution imagery and high resolution spaceborne imagery (WorldView-3). In this study, we assess the initial fire severity in the largest observed boreal forest fire (5000 ha) of the 2017 season in the intensive logging area of the Quebec province. We conducted an extensive field campaign of 90 plots where the composite burn index (CBI), char height, and other variables were collected in order to calibrate remotely sensed data that has been used to map at the initial burn severity of the fire. Preliminary results of object-oriented classification of the fire, calibrated with in situ data, proved to be a potentially highly effective mean of assisting salvage logging management.
Yan Boucher
added a research item
De 2005 à 2010, près de 1,7 million d’hectares de forêts ont été brûlés au Québec. Une vaste proportion de ces peuplements ont nécessité des travaux de remise en production. Présentement, d’après des études fragmentaires qui indiquent que les jeunes forêts dominées par l’épinette noire ont un faible potentiel de régénération, les pessières âgées de moins de 50 ans sont systématiquement reboisées. Nous avons réalisé une étude afin d’approfondir la question et d’évaluer si d’autres variables, telles que la sévérité des feux, la composition des strates muscinale, herbacée et arbustive ou les caractéristiques du peuplement, influencent la régénération de l’épinette noire après feu.
Yan Boucher
added a research item
La forêt boréale forme le plus vaste biome de la planète et assure des services économiques, sociaux et écologiques indispensables au développement de la biosphère. Les changements climatiques et l'exploitation forestière à grande échelle sont des menaces potentielles à la capacité du biome à procurer ces services. Il apparaît alors pertinent d'évaluer comment les écosystèmes de la forêt boréal réagiront à ces perturbations. L'identification des mécanismes de résilience opérant à travers les échelles de temps et d'espace est l'étape initiale vers une meilleure compréhension des réactions du système. La résilience d'un écosystème peut-être définie comme une propriété lui permettant de se réorganiser dans le temps lorsqu'il fait face à des perturbations. Dans cette synthèse, j'examine comment se manifeste la résilience des écosystèmes forestiers boréaux en fonction des échelles de temps (saison, succession, long terme) et d'espace (arbre, peuplement, paysage, biome). Pour ce faire, j'évalue la résilience des principaux écosystèmes forestiers du système boréal (pessières, pinèdes et sapinières) en réponse aux perturbations naturelles majeures que sont les feux et les épidémies de tordeuses des bourgeons de l'épinette (TBE). Les pratiques forestières (coupe, suppression des feux) et leurs interactions avec le régime des perturbations naturelles sont également étudiées afin d'évaluer leurs conséquences sur la résilience. L'étude permet d'évaluer que la résilience spatio-temporelle des écosystèmes dominés par l'épinette noire et le pin gris dépend étroitement du régime des feux et des conditions climatiques. Les sapinières sont très résiliente grâce à leur mécanisme de régénération et au contrôle des infestations exercé par la faune avienne. La diversité des groupes fonctionnels à l'intérieur de la forêt boréale est faible et la rend vulnérable aux 4 changements si des espèces disparaissent du système. L'influence anthropique a des impacts importants sur la résilience de la forêt boréale. Les perturbations en rafale comme celles formées par l'interaction entre les coupes et les perturbations naturelles érodent la résilience et peuvent entraîner le basculement du système vers des états alternatifs appauvris écologiquement. La suppression des feux pourrait provoquer des pertes importantes de résilience dans la forêt boréale exploitée. Finalement, l'utilisation de nouvelles approches de gestion, comme l'aménagement écosystémique, permettra de favoriser la résilience et fournira un tampon contre les perturbations extrêmes à venir. La résilience permettra de conserver les services procurés par la forêt boréale de même que le développement durable des systèmes socio-économiques de la biosphère.
Yan Boucher
added a research item
Clearcutting practices combined with the predicted increase in fire activity may induce post-fire regeneration failure in boreal forest landscapes. This study aims (1) to evaluate if recently managed landscape by clear cut logging is susceptible to be affected by post-fire regeneration failure; and (2) to explore the ecological drivers of black spruce (Picea mariana (Mill.) BSP) post-fire regeneration. In 2014, we surveyed the regeneration of 36 stands in northwestern Quebec that had burned in a major fire in 2005. Fire severity was evaluated for each site with the differenced Normalized Burn Ratio. Using linear models, we explored the relationship between environmental variables (fire severity, pre-fire stand maturity, nature of the seedbed, and physiographic variables) and black spruce post-fire regeneration. Black spruce post-fire seedling density was highly variable (range: 25–16 000 seedlings/ha; mean ± standard deviation: 4549 seedlings/ha ± 4752) within the studied fire, but did not significantly differ between stands that had been logged 50 years prior to fire and those that were mature prior to the 2005 fire. However, post-fire regeneration failure (defined as <40% stocking that corresponds in our study region to a regeneration density <1750 seedlings/ha) was observed in 48% of the stands that had been logged, but only in 29% of the stands that were mature prior to the fire. The presence of residual trees left after clearcutting may explain why regeneration level was relatively good (>50%) in stands affected by past logging activities. Our study illustrates how biological legacies, environmental conditions and fire severity determine post-fire recovery and resilience of black spruce-dominated ecosystems of eastern Canada. By identifying the drivers of post-fire regeneration success, our study will help forest managers allocating resources where restoration of productive forest are truly needed.
Yan Boucher
added a project goal
This study aims to develop a predictive tool for black spruce post-fire regeneration using stand disturbance history, and climate/site conditions. First, we want to developed a theoretical model that combined spatial variables (stand/site/climate conditions) commonly used by forest managers in eastern Canada, a fire severity index (“differenced normalized burn ratio”, or dNBR) and variables collected by in situ sampling (residual organic matter, tree age, twig severity index). Second, we will developed a spatially explicit model to predict post-fire regeneration using only spatial variables readily available in existing datasets. Our model will allow to incorporate climatic scenarios and will permit to evaluate post-fire resilience and productivity of boreal forest in a context of global change.