Tolerance of an expanding subarctic shrub, Betula glandulosa, to simulated caribou browsing

Densification of the shrub layer has been reported in many subarctic regions, raising questions about the implication for large herbivores and their resources. Shrubs can tolerate browsing and their level of tolerance could be affected by browsing and soils productivity, eventually modifying resource availability for the caribou. Our objective was to assess the compensatory growth potential of a subarctic shrub, Betula glandulosa Michx., in relation with caribou browsing and nutriment availability for the plants. We used a simulated browsing (0, 25 and 75% of available shoots) and nitrogenfertilisation (0 and 10 g m22) experiment to test two main hypotheses linking tolerance to resource availability, the Compensatory Continuum Hypothesis and the Growth Rate Hypothesis as well as the predictions from the Limiting Resource Model. We seek to explicitly integrate the relative browsing pressure in our predictions since the amount of tissues removed could affect the capacity of long-lived plants to compensate. Birches fully compensated for moderate browsing with an overall leaf biomass similar to unbrowsed birches but undercompensated under heavy browsing pressure. The main mechanism explaining compensation appears to be the conversion of short shoots into long shoots. The leaf area increased under heavy browsing pressure but only led to undercompensation. Fertilisation for two consecutive years did not influence the response of birch, thus we conclude that our results support the LRM hypothesis of equal tolerance under both high and low nitrogen availability. Our results highlight that the potential for compensatory growth in dwarf birch is surpassed under heavy browsing pressure independently of the fertilisation regime. In the context of the worldwide decline in caribou herds, the reduction in browsing pressur

Spatial extent of neighboring plants influences the strength of associational effects on mammal herbivory

There is high variability in the level of herbivory between individual plants from the same species with potential effects on population dynamics, community composition, and ecosystem structure and function. This variability can be partly explained by associational effects (i.e., the impact of the presence of neighboring plants on the level of herbivory experienced by a focal plant) but it is still unclear how the spatial scale of plant neighborhood modulates foraging choice of herbivores, an inherently spatial process in itself. Using a meta-analysis, we investigated how spatial scale modifies associational effects on the susceptibility to browsing by herbivores with movement capacities similar to deer. From 2496 articles found in literature databases, we selected 46 studies providing a total of 168 differences of means in damage by herbivores or survival to woody plants (mostly) with and without neighboring plants. Spatial scales were reported as distance between plants or as plot size. We estimated the relationships between the effect sizes and spatial scale, type of associational effects, and nature of the experiment using meta-analysis mixed models. The strength of associational effects declined with increasing plot size, regardless of the type of associational effects. Associational defenses (i.e., decrease in herbivory for focal plants associated with unpalatable neighbors) had stronger magnitude than associational susceptibilities. The high remaining heterogeneity among studies suggests that untested factors modulate associational effects, such as nutritional quality of focal and neighboring plants, density of herbivores, timing of browsing, etc. Associational effects are already considered in multiple restoration contexts worldwide, but a better understanding of these relationships could improve their use in conservation, restoration, and forest exploitation when browsing is a concern. This study is the first to investigate spatial patterns of associational effects across species and ecosystems, an issue that is essential to determine differential herbivory damages among plants

An experimental study of how variation in deer density affects vegetation and songbird assemblages of recently harvested boreal forests

Intense browsing by abundant large herbivores can threaten the ecological integrity of ecosystems by inducing modifications in the structure and composition of vegetation that trigger trophic cascades affecting plant and animal communities. We investigated the relationships between density of white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)), forest succession after clear-cut, and songbird communities on Anticosti Island, Quebec, Canada. We hypothesized that lower deer densities would alter the trajectory of forest succession after clear-cutting and lead to a rapid recovery of habitat attributes favorable to songbirds associated with a dense complex shrub layer. Six years after establishing a controlled browsing experiment (0, 7.5, 15, and >27 deer·km–2) in recent clearcuts, reducing deer densities ≤7.5 deer·km–2 initiated the restoration of balsam fir (Abies balsamea (L.) Mill.) forests and increased the regeneration of paper birch (Betula papyrifera Marshall). Increasing birch ground cover from 10% to 20% increased songbird total abundance, species richness, and diversity by 17%, 39%, and 31%, respectively. Alder Flycatcher (Empidonax alnorum Brewster, 1895) was only present at ≤7.5 deer·km–2 and strongly associated with birch regeneration. The regeneration of browse-resistant plants such as white spruce (Picea glauca (Moench) Voss) in some areas at high deer density favored the maintenance of many shrub-dependent songbirds but also species usually associated with forest canopy. Active management of deer populations in Canadian harvested boreal forests will mitigate losses in vegetation and songbirds caused by over-browsing.Le broutement intensif par de nombreux grands herbivores peut menacer l’intégrité écologique d’écosystèmes en induisant des modifications de la structure et de la composition de la végétation qui déclenchent des cascades trophiques ayant des incidences sur les communautés végétales et animales. Nous nous sommes penchés sur les liens entre la densité du cerf de Virginie (Odocoileus virginianus (Zimmermann, 1780)), la succession forestière après la coupe à blanc et les communautés d’oiseaux chanteurs sur l’île d’Anticosti (Québec, Canada). Nous avons émis l’hypothèse que de plus faibles densités de cerfs modifieraient la trajectoire de succession forestière après une coupe à blanc et mèneraient au rétablissement rapide des attributs d’habitat favorables aux oiseaux chanteurs associés à une strate arbustive complexe et dense. Six ans après l’établissement d’une expérience de broutement contrôlé (0, 7,5, 15 et >27 cerfs·km–2) dans des coupes récentes, la réduction des densités de cerfs à ≤7,5 cerfs·km–2 s’est traduite par le début du rétablissement des forêts de sapin baumier (Abies balsamea (L.) Mill.) et une régénération accrue du bouleau à papier (Betula papyrifera Marshall). Un passage de la couverture de bouleau de 10 % à 20 % s’est traduit par des augmentations de l’abondance totale d’oiseaux chanteurs, de la richesse spécifique et de la diversité de 17 %, 39 % et 31 %, respectivement. Le moucherolle des aulnes (Empidonax alnorum Brewster, 1895) n’était présent qu’à des densités ≤7,5 cerfs·km–2 et était fortement associé à la régénération du bouleau. La régénération de plantes résistantes au broutement, telles que l’épinette blanche (Picea glauca (Moench) Voss) dans certaines zones à forte densité de cerfs a favorisé le maintien de nombreux oiseaux chanteurs dépendants des arbustes, mais également d’espèces généralement associées à la canopée. La gestion active des populations de cerfs dans les forêts boréales canadiennes exploitées atténuera les pertes de végétation et d’oiseaux chanteurs causées par le surbroutemen

Winter severity modulates the benefits of using a habitat temporally uncoupled from browsing

Resources whose abundance is not affected by the density of the consumer population, namely donor-controlled resources, are ubiquitous. Donor-controlled resources can act as food subsidies when they sustain consumer populations at higher densities than what would be predicted without donorcontrolled dynamics. Herbivore populations that have access to food subsidies may reach and maintain high densities, with potential major ecological and economic consequences. A better understanding of the roles of food subsidies on temperate herbivores will likely be achieved by simultaneously taking into account other drivers of demographic variations such as winter severity. Here, we tested the hypothesis that the use of a donor-controlled food resource that may act as a food subsidy, namely balsam fir (Abies balsamea), and winter severity act together to shape the patterns of overwinter mass loss in a large herbivore population (white-tailed deer, Odocoileus virginianus). We monitored weather conditions, diet, habitat use, and mass loss of female deer during two highly contrasted winters. During an exceptionally milder winter, characterized by shallower snow depth and warmer windchill temperatures, female deer shifted their diet toward resources usually covered by snow during typical winters. Surprisingly, the rate of body mass loss remained similar during the milder and the harsher winter. The rate of body mass loss rather decreased with the use of balsam fir stands during the harsher winter, but increased with that same variable during the milder winter. Our study revealed that deer can alleviate overwinter mass loss by using a donor-controlled habitat type temporally uncoupled from browsing, but that this benefit is climate dependent. This study represents an additional step to address the largely unexplored concept of how temporal uncoupling between resources and consumer dynamics may contribute to sustain consumer populations at higher densities than predicted without considering donor-controlled dynamics

Spatial correlations between browsing on balsam fir by white-tailed deer and the nutritional value of neighboring winter forage

Associational effects, that is, the influence of neighboring plants on herbivory suffered by a plant, are an outcome of forage selection. Although forage selection is a hierarchical process, few studies have investigated associational effects at multiple spatial scales. Because the nutritional quality of plants can be spatially structured, it might differently influence associational effects across multiple scales. Our objective was to determine the radius of influence of neighbor density and nutritional quality on balsam fir (Abies balsamea) herbivory by white-tailed deer (Odocoileus virginianus) in winter. We quantified browsing rates on fir and the density and quality of neighboring trees in a series of 10-year-old cutovers on Anticosti Island (Canada). We used cross-correlations to investigate relationships between browsing rates and the density and nutritional quality of neighboring trees at distances up to 1,000 m. Balsam fir and white spruce (Picea glauca) fiber content and dry matter in vitro true digestibility were correlated with fir browsing rate at the finest extra-patch scale (across distance of up to 50 m) and between cutover areas (300–400 m). These correlations suggest associational effects, that is, low nutritional quality of neighbors reduces the likelihood of fir herbivory (associational defense). Our results may indicate associational effects mediated by intraspecific variation in plant quality and suggest that these effects could occur at scales from tens to hundreds of meters. Understanding associational effects could inform strategies for restoration or conservation; for example, planting of fir among existing natural regeneration could be concentrated in areas of low nutritional quality

Uncovering the minor contribution of land-cover change in upland forests to the net carbon footprint of a boreal hydroelectric reservoir

Hydropower in boreal conditions is generally considered the energy source emitting the least greenhouse gas per kilowatt-hour during its life cycle. The purpose of this study was to assess the relative contribution of the land-use change on the modification of the carbon sinks and sources following the flooding of upland forested territories to create the Eastmain-1 hydroelectric reservoir in Quebec’s boreal forest using Carbon Budget Model of the Canadian Forest Sector. Results suggest a carbon sink loss after 100 yr of 300,000 ± 100,000 Mg CO2 equivalents (CO2e). A wildfire sensitivity analysis revealed that the ecosystem would have acted as a carbon sink as long as <75% of the territory had burned over the 100-yr-long period. Our long-term net carbon flux estimate resulted in emissions of 4 ± 2 g CO2e kWh−1 as a contribution to the carbon footprint calculation, one-eighth what was obtained in a recent study that used less precise and less sensitive estimates. Consequently, this study significantly reduces the reported net carbon footprint of this reservoir and reveals how negligible the relative contribution of the land-use change in upland forests to the total net carbon footprint of a hydroelectric reservoir in the boreal zone can be

Management of forest regeneration in boreal and temperate deer-forest systems : challenges, guidelines and research gaps

Heavy browsing pressure from large ungulates is a multicontinent phenomenon that causes regeneration failure of many palatable tree species and induces important socioeconomic and ecological impacts in forest ecosystems. The development of forest management practices that address adequately this issue, however, remains scarce and challenging because (1) large herbivores are both a resource and a source of disturbance; (2) the management of forests and ungulate populations remains largely disconnected in practice; and (3) we still lack a good understanding of the role of critical factors, especially deer densities, vegetation attributes, and their interactions, on the magnitude of browsing damages on forest regeneration. We bring new insights into these challenging issues by critically reviewing the current methods used by managers and conservationists to mitigate deer impacts on forest regeneration, emphasizing the spatial scale at which these methods are undertaken. Specifically, we review management actions at multiple scales on both deer populations (e.g., hunting) and vegetation (e.g., silvicultural treatments) that are common to most deer–forest systems and, for that reason, deserve priority investigation. We identify strengths and limitations of current management actions and highlight the main research gaps. Based on this review, we propose a new integrated management scheme that explicitly addresses: (1) the integration and prioritization of management actions, (2) the development of adaptive management plans, and (3) the participation of stakeholders. Conflicting demands by different stakeholders have challenged the effectiveness of management strategies in deer–forest systems. To reverse this situation, we advocate for a shift of paradigm and the development of integrated strategies that (1) bridge the gap between management actions and the design of in situ experiments and (2) coordinate actions at multiple spatial scales on both deer populations and forests. We propose a new framework informed by key objectives and grounded in the adaptive management paradigm to support this transition, and suggest a research agenda for the next decade(s)

Saint-Camille : Récit d’une expérience de co-construction de la connaissance

Ce texte présente l’expérience du projet Ateliers des savoirs partagés mené en collaboration par une équipe du Centre de recherche sur les innovations sociales (CRISES) et le P'tit bonheur de Saint-Camille, auquel ont participé des leaders et des citoyens de la communauté. Cette expérience s’est déroulée entre septembre 2012 et octobre 2014 avec l'appui financier du ministère de l'Éducation, du Loisir et des Sports (MELS). L’expérience a cherché à dégager les principales composantes du modèle d'action mis en œuvre à Saint-Camille afin, d'une part, de le transmettre aux nouveaux résidents de cette communauté et, d'autre part, d'identifier les éléments susceptibles d'inspirer d'autres communautés qui éprouvent le besoin d'entamer des processus de revitalisation.This paper presents the experience of the Knowledge Sharing Workshops (“Ateliers des savoirs partagés”) carried out by a team formed by participants from the Center for Research on Social Innovations (Centre de recherche sur les innovations sociales, CRISES) and the P'tit bonheur of Saint-Camille. This experience was held on a partnership basis and was attended by academic researchers as well as leaders and citizens of the community. It took place between September 2012 and October 2014 and was financed by the Québec Ministry of Education, leisure and Sports. The experience aimed to identify the main components of the model of action implemented throughout the years by the community of Saint-Camille in order to transfer it to the new residents of the community and to draw out sources of inspiration for other communities that are triggering process of revitalization. Key words: Saint-Camille, Local development, Rural development, Space based development, Community, Distributed leadership, Governanc