Growth of tree species and hydrology in managed forested peatlands, Quebec

Le bilan hydrique des tourbières forestières est régi par une combinaison complexe de processus hydrologiques. Relativement stable en milieu naturel, ce bilan est facilement bouleversé par les activités d’aménagement forestier qui affectent le couvert végétal. Cette thèse de doctorat avait pour objectif d’étudier certaines interrelations existant entre la productivité forestière, la compétition pour les ressources et l’hydrologie des tourbières forestières du Québec. Le premier chapitre visait à déterminer s’il était pertinent d’utiliser le drainage forestier afin de transformer des pessières noires improductives en sites productifs. Les résultats ont démontré que même si ce traitement avait significativement augmenté la croissance de certains arbres, seul le drainage intensif utilisant des fossés rapprochés permettrait la conversion de tels peuplements. Les quatre autres chapitres visaient à évaluer l’influence de la végétation sur le contrôle des processus hydrologiques et indirectement sur la croissance forestière. La nappe phréatique a été mesurée dans une tourbière forestière pré-mature afin d’évaluer son comportement à la suite du drainage et à la récolte (Chapitre 2). Des mesures comparables ont été effectuées afin de mesurer la remontée de la nappe phréatique causée par l’éclaircie précommerciale sur des sites humides drainées et fortement régénérés (Chapitre 3). Ces deux études ont démontré l’influence significative de la végétation forestière sur le contrôle de la nappe phréatique en milieux forestiers humides. Puisque cette végétation possède une influence évidente sur la nappe phréatique, la croissance d’une tige devrait être favorisée par la présence immédiate de voisins. Le rôle du drainage biologique (Chapitre 4) ainsi que l’effet de la présence de compétition (Chapitre 5) sur la croissance ont été évalués pour des sites drainés. Il a été démontré que le pouvoir de contrôle de la nappe phréatique que possède la végétation est favorable à la croissance forestière, mais uniquement dans certaines situations particulières. Il semble donc pertinent de recommander des pratiques sylvicoles qui préservent une proportion considérable de la végétation sur les tourbières forestières.The water budget of forested peatland sites is regulated by a complex combination of hydrological processes. Relatively stable in natural environments, this budget is exposed to major changes by forest management activities affecting the tree canopy. This Ph.D. thesis aimed to study the specific interrelations existing between growth and yield of tree species, above-ground competition, and hydrology of Quebec forested peatlands. The first chapter aimed to determine the pertinence of using drainage to transform unproductive black spruce stands into productive ones. Results showed that even if tree growth was significantly increased by drainage, only intensive drainage using narrow ditch spacing would enable stand productivity improvement. The four other chapters intended to evaluate the influence of the vegetation on the regulation of hydrological processes and, indirectly, tree growth. The water table has been monitored on a pre-mature forested peatland site to evaluate its behaviour following drainage and harvesting (Chapter 2). Comparable water table monitoring has been done in densely regenerated post-harvest and drained peatland sites to measure the watering-up after precommercial thinning (Chapter 3). Both studies demonstrated the valuable water table regulation capacities of the treed vegetation in forested peatlands. Since this vegetation has an evident influence on soil growing conditions, tree growth should be affected by the presence of neighbours. The role of biological drainage (Chapter 4) and the presence of competition (Chapter 5) on growth have been evaluated for drained sites. The water table regulation power of the vegetation stratum was found to be favourable to tree growth, but only in specific situations. Management practices that preserve notable amount of vegetation on forested peatland stands seem to be the most pertinent guideline that should be considered in these fragile ecosystems

Home education in Quebec : family first

In Canada, until now, no studies have focused on the practice of home education in the francophone province of Quebec. While the home-educating population in that province is tangible, it has remained largely unknown. Quebec’s distinctive character on three fronts political, historical and cultural make the application of results from the rare Canadian studies or data from the US home-educating population seem inappropriate. This research, conducted by questionnaire in 2003, documented the sociodemographic characteristics of Quebec’s home-educating families and their motivations for home education. Beginning with a portrait of Quebec’s particular context, this article presents the motivations underlying the choice of home education expressed by 203 Quebec families. The reasons why these families have chosen to homeschool are many and diverse; parents’ rationales for their choices are wide-ranging and multidimensional. One particularity of the results is that no religious, philosophical or anti-state viewpoint seems to dominate the combined discourse. Seven motivational factors for home education were identified. Collectively, the respondents express the following as their main motivations for home educating their children: a desire to pursue a family educational project; an objection to the organisational structure of the school system; a desire to offer curriculum enrichment; and finally, a preoccupation with their children’s socioaffective development

L'école à la maison au Québec : l'expression d'un choix familial marginal

L'éducation à domicile est une option éducative marginale, quoique légale et présente à travers le monde. Au Québec, jusqu'ici, aucune étude approfondie n'avait décrit cette pratique et la population des familles concernées était inconnue. Cet article porte sur les raisons du choix de l'«école à la maison», exprimées par 203 familles québécoises au moyen d’un questionnaire. Cette enquête, réalisée en 2003, visait à documenter les conceptions de l'éducation, les raisons du choix, l'expérience éducative et les caractéristiques sociodémographiques des familles. Les raisons évoquées sont multiples et hétérogènes. Les rationnels décisionnels des parents sont variés et multidimensionnels. Une des particularités de ces résultats est qu'aucune voix religieuse, anti-étatique ou philosophique ne semble dominer le discours des parents-éducateurs québécois. Pour l'ensemble des participants, les principaux facteurs à la base de ce choix sont un désir de poursuivre un projet éducatif familial, une objection aux modes d'organisation du système scolaire, une volonté d'offrir de l'enrichissement et un souci du développement socioaffectif des enfants.Home schooling is a borderline, though legal, option that is exercised throughout the world. Until now, there has been no in-depth study of this practice in Quebec and there has been no head count of the families concerned. This article deals with the reasons for choosing home schooling, as given by 203 Quebec families who responded to a questionnaire on the subject. The survey, carried out in 2003, was designed to document the families` representation of education, the reasons for their choice, their educational experience and their socio-demographic profiles. The reasons they gave were both numerous and diversified. The rationale of the parents’ decisions is both varied and multidimensional. One of the particularities of the results is that the discourse of these Quebec parental educators seems quite devoid of any religious, anti-State or philosophical overtones. For the participants as a whole, the basic factors that largely determined their choice were their desire to implement a family educational project, their objection to the modes of organization of the school system, a desire to offer an enriched learning experience and a concern with the socio-affective development of their children

Influence of gender on people with disabilities’ work relationships : prospects for ergonomics interventions

Norms and values embedded in what is referred to as ‘institutionalised gender,’ defined by the distribution of power between genders in the political, educational, religious, medical, cultural or social institutions of a society, exist even today. The above mentioned influential institutions shape societal norms that define, reproduce and justify differing expectations and opportunities for women, men, girls and boys. Using qualitative methods, 41 semi-structured interviews among employed people with deafness/hard of hearing (DHH), blindness/low vision, motor disabilities, or chronic pain from three administrative regions of Québec (Montréal, Outaouais, and Montérégie) were analysed. The results show that while gender is omnipresent in participants’ remarks, it is not necessarily associated with exclusion from employment, but most certainly with perpetuating some forms of inequity in work situations. Solutions to raise awareness among ergonomists working with people with disabilities are suggested.Encore aujourd’hui, il existe des normes et des valeurs inscrites dans ce qui est appelé le « genre institutionnalisé », défini par la répartition du pouvoir entre les sexes dans les institutions politiques, éducatives, religieuses, médicales, culturelles ou sociales d’une société. Ces institutions influentes façonnent les normes sociales qui définissent, reproduisent et justifient souvent des attentes et des opportunités différentes pour les femmes et les hommes et les filles et les garçons. C’est à partir d’une méthodologie qualitative que 41 entrevues semi-dirigées de participants en emploi présentant une surdité, une cécité, une difficulté motrice ou des douleurs de trois régions administratives au Québec, Canada (Montréal, l’Outaouais et la Montérégie) ont été analysées. Les résultats montrent que même si le genre est omniprésent dans le discours des participants, il n’est pas nécessairement associé à l’exclusion en emploi, mais certainement au maintien de formes d’iniquités dans les situations de travail. Des pistes de solutions sont suggérées pour sensibiliser les ergonomes dans leurs interventions auprès de populations en situation de handicap

Impacts of high precipitation on the energy and water budgets of a humid boreal forest

The boreal forest will be strongly affected by climate change and in turn, these vast ecosystems may significantly impact global climatology and hydrology due to their exchanges of carbon and water with the atmosphere. It is now crucial to understand the intricate relationships between precipitation and evapotranspiration in these environments, particularly in less-studied locations characterized by a cold and humid climate. This study presents state-of-the-art measurements of energy and water budgets components over three years (2016–2018) at the Montmorency Forest, Québec, Canada: a balsam fir boreal forest that receives ∼1600 mm of precipitation annually (continental subarctic climate; Köppen classification subtype Dfc). Precipitation, evapotranspiration and potential evapotranspiration at the site are compared with observations from thirteen experimental sites around the world. These intercomparison sites (89 study-years) encompass various types of climate and vegetation (black spruces, jack pines, etc.) encountered in boreal forests worldwide. The Montmorency Forest stands out by receiving the largest amount of precipitation. Across all sites, water availability seems to be the principal evapotranspiration constraint, as precipitation tends to be more influential than potential evapotranspiration and other factors. This leads to the Montmorency Forest generating the largest amount of evapotranspiration, on average ∼550 mm y−1. This value appears to be an ecosystem maximum for evapotranspiration, which may be explained either by a physiological limit or a limited energy availability due to the presence of cloud cover. The Montmorency Forest water budget evacuates the precipitation excess mostly by watershed discharges, at an average rate of ∼1050 mm y−1, with peaks during the spring freshet. This behaviour, typical of mountainous headwater basins, necessarily influence downstream hydrological regimes to a large extent. This study provides a much needed insight in the hydrological regimes of a humid boreal-forested mountainous watershed, a type of basin rarely studied with precise energy and water budgets before

When Should I Use my Active Workstation? The impact of Physical Demand and Task Difficulty on IT Users’ Perception and Performance

The seated position in our daily computer interactions has been identified as a major threat for health. Active workstations have been proposed as a healthy solution to these problems. However, research findings on the effects of such workstations on users’ productivity is not conclusive. We argue that physical demand and task difficulty play a role in influencing IT users’ performance and perceptions when using active workstations. An experiment manipulating task difficulty, direct and indirect physical demands was performed. Results suggest that task difficulty moderates the relationships between physical demand (direct and indirect) and users’ perceptions and performance. Findings will help organizations and employees determine if it is appropriate for them to use active workstations

L'école à la maison au Québec : l'expression d'un choix familial marginal

L'éducation à domicile est une option éducative marginale, quoique légale et présente à travers le monde. Au Québec, jusqu'ici, aucune étude approfondie n'avait décrit cette pratique et la population des familles concernées était inconnue. Cet article porte sur les raisons du choix de l'« école à la maison », exprimées par 203 familles québécoises au moyen d’un questionnaire. Cette enquête, réalisée en 2003, visait à documenter les conceptions de l'éducation, les raisons du choix, l'expérience éducative et les caractéristiques sociodémographiques des familles. Les raisons évoquées sont multiples et hétérogènes. Les rationnels décisionnels des parents sont variés et multidimensionnels. Une des particularités de ces résultats est qu'aucune voix religieuse, anti-étatique ou philosophique ne semble dominer le discours des parents-éducateurs québécois. Pour l'ensemble des participants, les principaux facteurs à la base de ce choix sont un désir de poursuivre un projet éducatif familial, une objection aux modes d'organisation du système scolaire, une volonté d'offrir de l'enrichissement et un souci du développement socioaffectif des enfants.Home schooling is a borderline, though legal, option that is exercised throughout the world. Until now, there has been no in-depth study of this practice in Quebec and there has been no head count of the families concerned. This article deals with the reasons for choosing home schooling, as given by 203 Quebec families who responded to a questionnaire on the subject. The survey, carried out in 2003, was designed to document the families' representation of education, the reasons for their choice, their educational experience and their socio-demographic profiles. The reasons they gave were both numerous and diversified. The rationale of the parents' decisions is both varied and multidimensional. One of the particularities of the results is that the discourse of these Quebec parental educators seems quite devoid of any religious, anti-State or philosophical overtones. For the participants as a whole, the basic factors that largely determined their choice were their desire to implement a family educational project, their objection to the modes of organization of the school system, a desire to offer an enriched learning experience and a concern with the socio-affective development of their children

Portrait des milieux humides altérés par les cannebergières du Centre-du-Québec

Au Québec, plus particulièrement dans la région du Centre-du-Québec, la culture de la canneberge connait un essor depuis une trentaine d’années. L’objectif de cette étude est de vérifier l’idée véhiculée selon laquelle de moins en moins de cannebergières sont établies en milieux humides. Une analyse cartographique rétrospective a été réalisée au sein de 9 municipalités de la région du Centre-du-Québec pour la période de 1990 à 2019. Cette analyse a révélé que même si de plus en plus de terres non humides sont converties en cannebergières depuis le début des années 2000 (alors que pendant les années 1990-2000, la destruction des milieux humides prédominait ; 58 %), près de la moitié des terres converties sont encore des milieux humides (45 % pour 2000-2013 et 45 % pour 2013-2019). De 2013 à 2019, cela se traduit par 433 ha de milieux humides transformés en lien avec la production de canneberges, dont 252 ha (58 %) étaient des marécages arborés riches et 145 ha (33 %) étaient des dénudés humides (tourbières ouvertes et marais). Ces résultats permettront d’améliorer la planification du développement des cannebergières à l’échelle régionale afin d’atteindre les objectifs de conservation des milieux humides souhaités par notre société.Cranberry production has increased steadily in Québec (Canada) over the last 30 or so years, notably in the Centre-du-Québec administrative region. The aim of the present study was to test the generally held opinion that cranberry farms are increasingly being established on non-wetland sites. A retrospective cartographic analysis was done for the period ranging from 1990 to 2019 in 9 municipalities in the Centre-du-Québec region. This analysis revealed that a higher percentage of cranberry farms have been established on non-wetland sites since the early 2000s, whereas during the 1990–2000 period, 58% of new production units were established in wetlands. However, wetlands still accounted for almost half of the land converted for production of this fruit (45% for both 2000–2013 and 2013–2019). For the 2013–2019 period alone, this translated to the loss of 433 ha of wetlands to cranberry production, of which 252 ha (58%) were species-rich treed swamps and 145 ha (33%) were peatlands and marshes. These results will inform the future development of cranberry farms at the regional scale and help ensure that current wetland conservation objectives are met

Performance of automated geoprocessing methods for culvert detection in remote Forest environments

Greater availability of digital elevation models (DEMs) derived from airborne light detection and ranging (LiDAR) has made it possible to map precisely hydrographic features such as streams over large watersheds. Road embankments are precisely detected, given that DEMs are especially accurate over open areas, while culverts are not. Consequently, mapped stream positions are often erroneous along and through these anthropogenic structures. The position of actual culverts is often imprecise, incomplete or unavailable for large territories; thus, there is a need to develop and evaluate automated methods to locate culvert positions by remote sensing. Six geoprocessing methods were tested and compared to field-based culvert positioning data gathered in forested areas. These methods rely on preprocessing of depressions, manipulation of road embankment elevation, or both. When exact locations of culverts were unknown, the ‘Breach Depressions’ algorithm (WhiteBox GAT) was most accurate in reducing omission and commission errors. Depending upon the expected stream flow regime, it was possible to reduce cumulative error from 10% to 30% by using this method compared to less effective methods. When exact locations of culverts were known, it was possible to reduce cumulative error from 20% to 45% by burning them into the DEM. Comparisons of two different methods revealed that no automated geoprocessing allowed accurate detection of poorly located culverts, i.e. where small streams deviated into road-side ditches. Despite automated geoprocessing methods that are available, a database geolocating all culverts within a territory is the best way to create exact hydrographic networks without road embankment influence.La grande disponibilité des modèles numériques de terrain (MNT) issus de la technologie LiDAR (light detection and ranging) a permis de cartographier des éléments hydrographiques comme de petits cours d’eau pour de grands bassins versants. La mise en forme des chemins est généralement bien détectée sur les MNT alors que les ponceaux qui permettent de faire passer l’eau sous les chemins ne le sont pas. En conséquence, les cours d’eau cartographiés sont souvent erronés et déviés le long des chemins. Le positionnement des ponceaux est souvent imprécis, incomplet ou tout simplement non disponible pour de larges territoires. Ainsi, il est essentiel de développer et d’évaluer des méthodes automatisées de détection des ponceaux. Six méthodes ont été testées et comparés à une base de données terrain de ponceaux en milieux forestiers. Ces méthodes se basent sur le prétraitement des dépressions, l’effacement des chemins ou une combinaison des deux. Lorsque la position exacte des ponceaux était inconnue, la méthode ‘Breach Depressions’ (WhiteBox GAT) était la plus performante afin de réduire les erreurs d’omission et de commission. En fonction du régime d’écoulement, il a été possible de réduire l’erreur de 10 à 30% comparativement à la méthode la moins performante. Lorsque la position exacte des ponceaux était connue, il a été possible de réduire l’erreur cumulative de 20 à 45% en brulant la mise en forme des chemins. Une comparaison a révélé qu’aucune méthode automatisée ne permet de détecter des ponceaux inadéquatement positionnés, par exemple à des endroits où des cours d’eau sont déviés dans des fossés. Malgré les méthodes automatisées disponibles, l’acquisition d’une base de données exhaustive localisant tous les ponceaux d’un territoire est la meilleure manière de générer un réseau hydrographique sans l’influence de la mise en forme des chemins

Surface network and drainage network : towards a common data structure

The surface network is an application of the Morse-Smale complex to digital terrain models connecting ridges and thalwegs of the terrain in a planar, undirected graph. Although it provides a topological structure embedding critical elements of the terrain, its application to morphological analysis and hydrology remains limited mainly because the drainage network is the most relevant structure for analysis and it cannot be derived from the surface network. The drainage network is a directed, hierarchical graph formed by streams. Ridges of the surface network are not equivalent to drainage divides, which are not contained in the drainage network, and there is no direct association between thalwegs and streams. Therefore, this paper proposes to extend the surface network into a new structure that also embeds the drainage network. This is done by (1) revising the definition of ridges so that they include drainage divides and (2) assigning a flow direction to each thalweg, taking into account spurious depressions to avoid flow interruption. We show that this extended surface network can be used to compute the flow accumulation and different hydrographic features such as drainage basins and the Strahler order. The drainage network extracted from the extended surface network is compared to drainage networks computed with the traditional D8 approach in three case studies. Differences remain minor and are mainly due to the elevation inaccuracy in flat or slightly convex areas. Hence, the extended surface network provides a richer data structure allowing the use of a common topological data structure in both terrain analysis and hydrology