Cycle des feux, vieilles forêts et aménagement en forêt boréale de l'est du Canada

Les feux de forêts constituent l'un des processus les plus importants de la forêt boréale en établissant les fondements d'une mosaïque dynamique de peuplements forestiers à l'intérieur de laquelle une multitude d'autres processus interagissent. En initiant une succession secondaire, ils déterminent en partie la composition, la structure et la répartition spatiale des différents types d'habitats rencontrés en forêt boréale. Voilà pourquoi il est souvent suggéré que les impacts des perturbations anthropiques (e.g. coupes) sur les paysages aménagés seront atténués si celles-ci émulent le mieux possible les patrons et processus normalement générés par les perturbations naturelles (e.g. feux de forêt). Le cycle des feux, défini comme le temps nécessaire à ce qu'une superficie cumulée égale au territoire à l'étude ait brûlé de nouveau, est un paramètre important du régime des feux puisqu'il détermine la proportion des classes d'âge à l'échelle du paysage. Or, les cycles des feux relativement longs documentés dans l'est du Canada suggéraient que les paysages forestiers produits au terme de la première rotation forestière industrielle seraient amputés d'une portion importante de la variété d'habitats qui caractérisent les paysages produits par les perturbations naturelles. L'objectif principal de cette thèse était donc de documenter le cycle des feux sur la Côte-Nord, une région caractérisée par une présence particulièrement importante de vieilles forêts, ainsi que ses répercussions sur la dynamique successionelle des principales espèces d'arbres et les implications sur l'aménagement forestier en forêt boréale de l'est du Canada. Dans un premier chapitre, nous avons évalué le cycle des feux sur la Côte-Nord ainsi que l'incertitude qui lui est associée à l'aide d'une approche par modélisation. Nous y comparons aussi trois méthodes d'analyses de survie pouvant être utilisées pour estimer le cycle des feux. Il s'est avéré que l'approche non-paramétrique, la régression de Cox, permet l'obtention d'une estimation plus robuste aux variations temporelles de l'activité des feux, la source de biais potentiel la plus importante. À l'aide de cette méthode, nous avons pu estimer à environ 227 ans le cycle des feux récent dans le territoire à l'étude, une valeur à laquelle est toutefois associée un intervalle de confiance à 95% de ±60 à 70 ans. Dans un second chapitre, nous avons isolé les facteurs responsables d'une hétérogénéité spatiale de la fréquence des feux sur la Côte-Nord, qui se sont avérés dépendre fortement de l'échelle spatiale à laquelle ils sont décrits en raison du caractère contagieux des feux de forêt. Il s'est avéré qu'au sein d'un même paysage, certaines grandes zones dominées par des versants exposés au sud étaient 2 à 6 fois plus susceptibles que d'autres, affectant ainsi la répartition de peuplements forestiers distincts au niveau de la composition et/ou de la structure. Nous avons ensuite testé l'influence de cette hétérogénéité sur la dynamique des peuplements au moyen d'analyses multivariées des communautés végétales. Nous avons ainsi tenté d'isoler l'influence du temps depuis le dernier feu en tant que tel de l'appartenance à un contexte où les feux sont plus ou moins fréquents. De façon générale, c'est seulement dans les zones à faible fréquence des feux que le principal spécialiste de fin de succession, le sapin baumier, arrive à supplanter l'espèce globalement la plus abondante en forêt boréale de l'est du Canada, l'épinette noire, en raison du temps depuis le dernier feu généralement plus long. Nos résultats suggèrent aussi que la succession de P. mariana vers A. balsamea peut se produire longtemps après ce qui est généralement couvert par les reconstitutions dendroécologiques de l'historique des feux dans ce type de paysages boréaux (>200-300 ans). En dernier lieu, nous nous sommes intéressés à un autre paysage forestier boréal, situés à l'extrême ouest du Québec en partie sur la portion nord de l'Abitibi et au sud de la Jamésie. Nous avons examiné la variabilité à plus long terme (6800 ans) de l'activité des feux au moyen d'une reconstitution paléoécologique basée sur les fragments de charbon enfouis dans les sédiments de lac stratifiés. Cette analyse nous a permis de décrire ce que nous soutenons être une plage de variabilité naturelle pertinente pour l'établissement de cibles d'aménagement, qui fut comparée à l'état actuel du paysage étudié. Nos résultats confirment les appréhensions selon lesquels l'aménagement néglige une importante proportion des paysages boréaux naturels, i.e. les vieilles forêts, puisque celles-ci semblent avoir occupé une portion importante de ce paysage au cours de l'ensemble de son histoire post-glaciaire, une réalité qui a rapidement été altérée au cours des trois dernières décennies de récolte extensive. \ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Feux de forêt, Côte-Nord, Abitibi, Québec, Aménagement forestier écosystémique, Épinette noire, Cycle des feux, Fréquence des feux, Paléoécologie, Analyses de survie

Captation des particules fines par les arbres : cas des grands parcs montréalais

La matière particulaire est un agent nocif pour la santé humaine et la réduction de sa concentration atmosphérique est nécessaire dans une approche de santé publique. L’atteinte de cet objectif passe par, entre autres, la captation des particules par la végétation. La question que nous nous sommes posés est: quel est le potentiel de captation des arbres publics dans la ville de Montréal. Comme site à l’étude, nous avons choisi les grands parcs, car leur végétation arborescente couvre un pourcentage important de leur surface. Le modèle de captation de la matière particulaire du logiciel i-Tree a été utilisé pour définir la capacité de purification de l’air selon les caractéristiques spécifiques de chaque parc. Ces caractéristiques comprennent l’indice de surface foliaire des arbres (LAI) et l’étendue des canopées, les conditions météorologiques ainsi que les concentrations des particules dans l’air. Plusieurs méthodes et techniques de calcul de ces paramètres ont été testés et les plus appropriées retenues pour le calcul des intrants. Les calculs ont été faits sur une base journalière pour l’ensemble de l’année 2017. Les résultats montrent que le total des particules captées pendant l’année 2017 s’élève à un peu plus que 3.5 tonnes pour les quatorze parcs évalués. Selon nos calculs, la majeure partie de ces particules a été lessivée au sol par les pluies et un faible pourcentage a été remis en circulation. Un test de validation des résultats in situ n’a pas été concluant. Il n’en demeure pas moins que les résultats sont similaires aux résultats des recherches effectuées dans d’autres villes Nord-Américaines avec le modèle d’i-Tree. Ces résultats montrent que le rôle des arbres pour la purification de l’air est important tout au moins localement. Les possibilités d’améliorer les méthodes de calcul des intrants du modèle de captation sont également discutées.Particulate matter is an agent harmful to human health and reducing its atmospheric concentration is necessary from a public health approach. Achieving this objective requires, among other things, the capture of particles by vegetation. Our research question was what is the potential of public trees in the city of Montreal for capturing such particles. We chose large parks as our study site, because trees cover a significant percentage of their surface. The particulate matter capture model of the i-Tree software was used to define the air purification capacity according to the specific characteristics of each park. These characteristics include tree leaf area index (LAI) and canopy extent, weather conditions, and particulate matter concentrations in the air. Several methods and techniques for calculating these parameters were tested and the most appropriate ones used for the calculation of inputs to the model. Calculations were made on a daily basis for the whole of 2017. The results show that just over 3.5 tonnes of particles were captured for the fourteen parks evaluated over this period. According to our calculations, most of these particles were leached to the ground by rain and a small percentage were put back into circulation. A validation test of the results in situ was inconclusive. The fact remains that the results are similar to those of research carried out in other North American cities with the i-Tree model. These results show that the role of trees for air purification is important at least locally. Possibilities for improving the methods of calculating the inputs for the capture model are also discussed

Implementation of a Parenting Coordination Pilot Project in Montreal, Canada: What Did We Learn?

For parents who experience high conflict following their separation or divorce, the various psychosocial and legal services provided by the government of Quebec or in the private sector have proven to be inadequate, resulting in an over-dependence on the court system and child protective services to provide solutions. In response to this social dilemma, the Quebec Ministry of Justice agreed in 2012 to fund a pilot project to determine if parenting coordination could provide some relief to the families and to the judicial system. A research team also had the mandate to evaluate the extent to which parenting coordination could eventually be integrated with other services being offered in both the public and private sectors. Between 2012 and 2014, ten families were followed by two parenting coordinators for a period ranging from six to 18 months. This article will present the interdisciplinary model put forward in the implementation of a parental coordination project, some highlights of the results of this pilot project and the recommendations that ensued.

Forest management is driving the eastern North American boreal forest outside its natural range of variability

Fire is fundamental to the natural dynamics of the North American boreal forest. It is therefore often suggested that the impacts of anthropogenic disturbances (eg logging) on a managed landscape are attenuated if the patterns and processes created by these events resemble those of natural disturbances (eg fire). To provide forest management guidelines, we investigate the long-term variability in the mean fire interval (MFI) of a boreal landscape in eastern North America, as reconstructed from lacustrine (lake-associated) sedimentary charcoal. We translate the natural variability in MFI into a range of landscape age structures, using a simple modeling approach. Although using the array of possible forest age structures provides managers with some flexibility, an assessment of the current state of the landscape suggests that logging has already caused a shift in the age-class distribution toward a stronger representation of young stands with a concurrent decrease in old-growth stands. Logging is indeed quickly forcing the studied landscape outside of its long-term natural range of variability, implying that substantial changes in management practices are required, if we collectively decide to maintain these fundamental attributes of the boreal forest

Earnings Management in the Charitable Sector: A Canadian Study

This article examines whether charitable organizations use discretionary accruals to manage their surplus or deficit. Linear regression was used to analyze the financial data of a broad sample of Canadian charitable organizations. Results showed that discretionary accruals were used to manage these income figures. This approach is compounded by the magnitude of grants, public benefit, and leverage. The results hold whether the charity anticipates a surplus or a deficit, but not if it displays a high level of public benefit. In that case, charities with an anticipated surplus increase their use of discretionary accruals to decrease earnings, whereas charities that anticipate a deficit are not inclined to manage their deficit toward zero. This study complements prior literature on nonprofits and shows that even though tax laws differ among countries, charity managers in various contexts are motivated to manage earnings and are influenced by various factors in doing so

Converging and diverging burn rates in North American boreal forests from the Little Ice Age to the present

Warning. This article contains terms, descriptions, and opinions used for historical context that may be culturally sensitive for some readers. Background. Understanding drivers of boreal forest dynamics supports adaptation strategies in the context of climate change. Aims. We aimed to understand how burn rates varied since the early 1700s in North American boreal forests. Methods. We used 16 fire-history study sites distributed across such forests and investigated variation in burn rates for the historical period spanning 1700-1990. These were benchmarked against recent burn rates estimated for the modern period spanning 1980-2020 using various data sources. Key results. Burn rates during the historical period for most sites showed a declining trend, particularly during the early to mid 1900s. Compared to the historical period, the modern period showed less variable and lower burn rates across sites. Mean burn rates during the modern period presented divergent trends among eastern versus northwestern sites, with increasing trends in mean burn rates in most northwestern North American sites. Conclusions. The synchronicity of trends suggests that large spatial patterns of atmospheric conditions drove burn rates in addition to regional changes in land use like fire exclusion and suppression. Implications. Low burn rates in eastern Canadian boreal forests may continue unless climate change overrides the capacity to suppress fire.Peer reviewe

Well-being of Canadian Veterans during the COVID-19 pandemic:cross-sectional results from the COVID-19 Veteran well-being study

Background: The impacts of the COVID-19 pandemic have disproportionally affected different population groups. Veterans are more likely to have pre-existing mental health conditions compared to the general Canadian population, experience compounded stressors resulting from disruptions to familial, social, and occupational domains, and were faced with changes in health-care delivery (e.g. telehealth). The objectives of this study are to assess (a) the mental health impact of COVID-19 and related life changes on the well-being of Veterans and (b) perceptions of and satisfaction with changes in health-care treatments and delivery during the pandemic. Methods: A total of 1136 Canadian Veterans participated in an online survey. Participants completed questions pertaining to their mental health and well-being, lifestyle changes, and concerns relating to the COVID-19 pandemic, as well as experiences and satisfaction with health-care treatments during the pandemic. Results: Results showed that 55.9% of respondents reported worse mental health functioning compared to before the pandemic. The frequency of probable posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, alcohol use disorder, and suicidal ideation were 34.2%, 35.3%, 26.8%, 13.0%, and 22.0%, respectively. Between 38.6% and 53.1% of respondents attributed their symptoms as either directly related to or exacerbated by the pandemic. Approximately 18% of respondents reported using telehealth for mental health services during the pandemic, and among those, 72.8% indicated a choice to use telehealth even after the pandemic. Conclusions: This study found that Veterans experienced worsening mental health as a result of the COVID-19 pandemic. The use of telehealth services was widely endorsed by mental health treatment-seeking Veterans who transitioned to virtual care during the pandemic. Our findings have important clinical and programmeadministrator implications, emphasizing the need to reach out to support veterans, especially those with pre-existing mental health conditions and to enhance and maintain virtual care even post-pandemic.</p

Well-being of Canadian Veterans during the COVID-19 pandemic: cross-sectional results from the COVID-19 Veteran well-being study

Background: The impacts of the COVID-19 pandemic have disproportionally affected different population groups. Veterans are more likely to have pre-existing mental health conditions compared to the general Canadian population, experience compounded stressors resulting from disruptions to familial, social, and occupational domains, and were faced with changes in health-care delivery (e.g. telehealth). The objectives of this study are to assess (a) the mental health impact of COVID-19 and related life changes on the well-being of Veterans and (b) perceptions of and satisfaction with changes in health-care treatments and delivery during the pandemic. Methods: A total of 1136 Canadian Veterans participated in an online survey. Participants completed questions pertaining to their mental health and well-being, lifestyle changes, and concerns relating to the COVID-19 pandemic, as well as experiences and satisfaction with health-care treatments during the pandemic. Results: Results showed that 55.9% of respondents reported worse mental health functioning compared to before the pandemic. The frequency of probable posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, alcohol use disorder, and suicidal ideation were 34.2%, 35.3%, 26.8%, 13.0%, and 22.0%, respectively. Between 38.6% and 53.1% of respondents attributed their symptoms as either directly related to or exacerbated by the pandemic. Approximately 18% of respondents reported using telehealth for mental health services during the pandemic, and among those, 72.8% indicated a choice to use telehealth even after the pandemic. Conclusions: This study found that Veterans experienced worsening mental health as a result of the COVID-19 pandemic. The use of telehealth services was widely endorsed by mental health treatment-seeking Veterans who transitioned to virtual care during the pandemic. Our findings have important clinical and programmeadministrator implications, emphasizing the need to reach out to support veterans, especially those with pre-existing mental health conditions and to enhance and maintain virtual care even post-pandemic

Well-being of Canadian Veterans during the COVID-19 pandemic:cross-sectional results from the COVID-19 Veteran well-being study

Background: The impacts of the COVID-19 pandemic have disproportionally affected different population groups. Veterans are more likely to have pre-existing mental health conditions compared to the general Canadian population, experience compounded stressors resulting from disruptions to familial, social, and occupational domains, and were faced with changes in health-care delivery (e.g. telehealth). The objectives of this study are to assess (a) the mental health impact of COVID-19 and related life changes on the well-being of Veterans and (b) perceptions of and satisfaction with changes in health-care treatments and delivery during the pandemic. Methods: A total of 1136 Canadian Veterans participated in an online survey. Participants completed questions pertaining to their mental health and well-being, lifestyle changes, and concerns relating to the COVID-19 pandemic, as well as experiences and satisfaction with health-care treatments during the pandemic. Results: Results showed that 55.9% of respondents reported worse mental health functioning compared to before the pandemic. The frequency of probable posttraumatic stress disorder, major depressive disorder, generalized anxiety disorder, alcohol use disorder, and suicidal ideation were 34.2%, 35.3%, 26.8%, 13.0%, and 22.0%, respectively. Between 38.6% and 53.1% of respondents attributed their symptoms as either directly related to or exacerbated by the pandemic. Approximately 18% of respondents reported using telehealth for mental health services during the pandemic, and among those, 72.8% indicated a choice to use telehealth even after the pandemic. Conclusions: This study found that Veterans experienced worsening mental health as a result of the COVID-19 pandemic. The use of telehealth services was widely endorsed by mental health treatment-seeking Veterans who transitioned to virtual care during the pandemic. Our findings have important clinical and programmeadministrator implications, emphasizing the need to reach out to support veterans, especially those with pre-existing mental health conditions and to enhance and maintain virtual care even post-pandemic.</p

Well-being of Canadian Armed Forces Veterans and Spouses of Veterans during the COVID-19 Pandemic: Protocol for a Prospective Longitudinal Survey

Background: The COVID-19 pandemic has resulted in significant changes to everyday life, including social distancing mandates, changes to health care, and a heightened risk of infection. Previous research has shown that Canadian Armed Forces (CAF) veterans are at higher risk of developing mental and physical health conditions. Veterans and their families may face unique social challenges that can compound with pandemic-related disruptions to negatively impact well-being. Objective: This study aims to longitudinally characterize the mental health of CAF veterans and spouses of CAF veterans throughout the pandemic and to understand the dynamic influences of pandemic-related stressors on psychological health over time. Methods: We employed a prospective longitudinal panel design using an online data collection platform. Study participation was open to all CAF veterans and spouses of CAF veterans residing in Canada. Participants were asked to complete a comprehensive battery of assessments representing psychological well-being, chronic pain, health care access patterns, physical environment, employment, social integration, and adjustment to pandemic-related lifestyle changes. Follow-up assessments were conducted every 3 months over an 18-month period. This study was approved by the Western University Health Sciences and Lawson Health Research Institute Research Ethics Boards. Results: Baseline data were collected between July 2020 and February 2021. There were 3 population segments that participated in the study: 1047 veterans, 366 spouses of veterans, and 125 veterans who are also spouses of veterans completed baseline data collection. As of November 2021, data collection is ongoing, with participants completing the 9-or 12-month follow-up surveys depending on their date of self-enrollment. Data collection across all time points will be complete in September 2022. Conclusions: This longitudinal survey is unique in its comprehensive assessment of domains relevant to veterans and spouses of veterans during the COVID-19 pandemic, ranging from occupational, demographic, social, mental, and physical domains, to perceptions and experiences with health care treatments and access. The results of this study will be used to inform policy for veteran and veteran family support, and to best prepare for similar emergencies should they occur in the future