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Questions: Does urbanization promote biotic differentiation or homogenization of swamp plant communities? What is the contribution of natives and exotics to swamp response to urbanization? Location: Quebec City, Canada. Methods: Plant communities of 34 swamps located in low, moderately or highly urbanized landscapes were sampled, and species classified into three exclusive groups: native wetland, native upland and exotic plants. Urbanization's influence on the richness of each plant group was assessed using mixed models. Between-site compositional similarities were calculated to identify variations in beta diversity with urbanization level using tests for homogeneity in multivariate dispersion. Beta diversity was further partitioned into species replacement and richness difference for each plant group. Finally, the relationships of ten environmental variables representing soil water saturation and microtopography with plant assemblages were determined by redundancy analysis. Results: Although the richness of exotics increased with urbanization intensity, revealing increasing propagule pressure, it remained six to 27 times lower compared to the richness of natives, which remained stable with urbanization. On the other hand, beta diversity increased with urbanization, with higher dissimilarities in species composition between highly urbanized swamps than between low-urbanized ones. This pattern resulted from high species replacement among natives, while richness difference mainly contributed to exotic beta diversity. Changes in plant assemblages were mostly associated with bryophyte cover and soil drainage and red mottle size, suggesting that hydrological conditions likely acted as a strong driver of swamp plant community response to urbanization. Conclusions: Swamp plant communities experienced biotic differentiation with increasing urbanization. This differentiation pattern likely was linked to the unpredict-able effect of urbanization on hydrological regimes, which

Overabundance of wild ungulates, especially exotic species, is a major threat to several ecosystems worldwide. While the response of forest vegetation to high density of herbivores has been well studied, far less is known about peatland vegetation. In this paper, we assessed the long term impact of white-tailed deer (Odocoileus virginianus) on plant communities of ombrotrophic (bog) and minerotrophic (fen) peatlands in eastern North America. Vegetation of five peatlands that have experienced high deer densities for at least 75 years was compared with that of five peatlands situated at proximity but on deer-free islands. We investigated deer impacts on plant species composition and cover, shrub height and cloudberry (Rubus chamaemorus) fruit/flower production and morphology. In bogs, white-tailed deer had no long-term impact on plant species assemblages, but reduced lichen cover and increased sedges and grasses cover as well as the surface area of bare peat. On the other hand, the floristic composition of fens differed significantly between sites where deer were present or absent. Plant diversity was greater in undisturbed fens than in disturbed fens, especially for shrubs, sedges and liverworts. No detrimental effects of browsing on shrub height were observed. Conversely, deer browsing seemed to have deleterious impacts on cloudberry fruit/flower production as well as on the number of leaves per individual. Overall, our results suggest that white-tailed deer had some important impacts on the vegetation of peatlands that could be harmful for the long-term conservation of peatland plant diversity.

Depuis son introduction, il y a plus d’une centaine d’années, le cerf de Virginie (Odocoileus virginianus Zimm.) a fortement perturbé la flore de l’île d’Anticosti. Les communautés forestières sont sans contredit celles qui ont été les plus affectées. Toutefois, le cerf exploite et perturbe aussi d’autres écosystèmes, comme les tourbières. Dans ce contexte, nous voulions savoir quelle serait la diversité végétale des tourbières à la suite du retrait du cerf. Pour ce faire, 53 exclos ont été mis en place en 2007 et suivis pendant 8 ans. Au total, 125 espèces végétales ont été identifiées dans l’ensemble des exclos en 2007 et 151 espèces après 8 ans d’exclusion du cerf, ce qui représente une hausse de 21 %. Le nombre d’espèces indicatrices, c’est-à-dire celles caractéristiques d’un habitat donné, a également augmenté, passant de 33 à 48, la hausse étant particulièrement importante dans les laggs (écotones entre la forêt et la tourbière). Le recouvrement des espèces préférées par le cerf a grandement augmenté, notamment celui du bouleau nain (Betula pumila L.) et de la sanguisorbe du Canada (Sanguisorba canadensis L.) (respectivement 2 et 8 fois). Au final, les tourbières de l’île d’Anticosti possèdent un potentiel de diversité végétale plus élevé qui peut s’exprimer avec l’arrêt du broutement par le cerf de Virginie., White-tailed deer (Odocoileus virginianus Zimm.) were introduced to Anticosti Island (Québec, Canada) more than 100 years ago, where they are now considered overabundant and have greatly modified the flora. While forest communities have been the most heavily affected, deer also use and disturb other ecosystems, such as peatlands. This study sought to determine the potential plant diversity of peatlands on the island in the absence of deer. To achieve this, 53 exclosures were established in 2007 and the vegetation monitored over an 8 year period. At the start of the study, 125 plant species were recorded, and after 8 years of deer exclusion this had risen by 21% to 151 species. Over the same period, the number of indicator species (i.e., species associated with a specific habitat) grew from 33 to 48, with the increase being particularly marked in the laggs (ecotones between forest and peatland). After 8 years of exclusion, the vegetation cover of species preferentially grazed by deer had also risen greatly, with bog birch (Betula pumila L.) increasing twofold and Canadian burnet (Sanguisorba canadensis L.), eightfold. In conclusion, peatlands on Anticosti Island have a potential for greater plant richness, which can be expressed after white-tailed deer exclusion.

Depuis son introduction, il y a plus d’une centaine d’années, le cerf de Virginie (Odocoileus virginianus Zimm.) a fortement perturbé la flore de l’île d’Anticosti. Les communautés forestières sont sans contredit celles qui ont été les plus affectées. Toutefois, le cerf exploite et perturbe aussi d’autres écosystèmes, comme les tourbières. Dans ce contexte, nous voulions savoir quelle serait la diversité végétale des tourbières à la suite du retrait du cerf. Pour ce faire, 53 exclos ont été mis en place en 2007 et suivis pendant 8 ans. Au total, 125 espèces végétales ont été identifiées dans l’ensemble des exclos en 2007 et 151 espèces après 8 ans d’exclusion du cerf, ce qui représente une hausse de 21 %. Le nombre d’espèces indicatrices, c’est-à-dire celles caractéristiques d’un habitat donné, a également augmenté, passant de 33 à 48, la hausse étant particulièrement importante dans les laggs (écotones entre la forêt et la tourbière). Le recouvrement des espèces préférées par le cerf a grandement augmenté, notamment celui du bouleau nain (Betula pumila L.) et de la sanguisorbe du Canada (Sanguisorba canadensis L.) (respectivement 2 et 8 fois). Au final, les tourbières de l’île d’Anticosti possèdent un potentiel de diversité végétale plus élevé qui peut s’exprimer avec l’arrêt du broutement par le cerf de Virginie., White-tailed deer (Odocoileus virginianus Zimm.) were introduced to Anticosti Island (Québec, Canada) more than 100 years ago, where they are now considered overabundant and have greatly modified the flora. While forest communities have been the most heavily affected, deer also use and disturb other ecosystems, such as peatlands. This study sought to determine the potential plant diversity of peatlands on the island in the absence of deer. To achieve this, 53 exclosures were established in 2007 and the vegetation monitored over an 8 year period. At the start of the study, 125 plant species were recorded, and after 8 years of deer exclusion this had risen by 21% to 151 species. Over the same period, the number of indicator species (i.e., species associated with a specific habitat) grew from 33 to 48, with the increase being particularly marked in the laggs (ecotones between forest and peatland). After 8 years of exclusion, the vegetation cover of species preferentially grazed by deer had also risen greatly, with bog birch (Betula pumila L.) increasing twofold and Canadian burnet (Sanguisorba canadensis L.), eightfold. In conclusion, peatlands on Anticosti Island have a potential for greater plant richness, which can be expressed after white-tailed deer exclusion.

This study investigated how hydrogeological setting influences aquifer–peatland connections in slope and basin peatlands. Steady-state groundwater flow was simulated using Modflow on 2D transects for an esker slope peatland and for a basin peatland in southern Quebec (Canada). Simulations investigated how hydraulic heads and groundwater flow exported toward runoff from the peatland can be influenced by recharge, hydraulic properties, and heterogeneity. The slope peatland model was strongly dominated by horizontal flow from the esker. This suggests that slope peatlands are dependent on the hydrogeological conditions of the adjacent aquifer reservoir, but are resilient to hydrological changes. The basin peatland produced groundwater outflow to the surface aquifer. Lateral and vertical peat heterogeneity due to peat decomposition or compaction were identified as having a significant influence on fluxes. These results suggest that basin peatlands are more dependent on recharge conditions, and could be more susceptible to land use and climate changes.

Questions : What are the spatial processes structuring plant trait composition in urban riparian forest communities at different spatial scales? What are the relative roles of local conditions (including historical aspects), landscape context and spatial processes in the community assembly of these forests? Location : Montréal, Québec, Canada. Methods : Species plant composition was inventoried in 57 riparian forests located along a gradient of urbanization. To analyse plant communities in terms of their trait composition, community-weighted means were calculated using eight functional traits. Forests were characterized by local (physical features, hydrological regime and historical disturbances) and landscape (surrounding land use) variables. Spatial processes structuring communities were assessed using Moran's eigenvector maps and asymmetric eigenvector maps. The relative importance of these three subsets (local, landscape and spatial variables) on tree, shrub and herb functional composition was quantified by variation partitioning using redundancy analyses. Results : Functional patterns in riparian forests resulted primarily from environmental filtering (local and landscape variables). Local conditions, especially flood intensity, exerted an overriding selection pressure on functional composition of riparian plant communities. Urbanization seemed to act indirectly on trait patterns through the alteration of hydrological disturbances caused by on-going and historical land transformation. Nevertheless, dispersal along rivers was also a significant structuring force, while overland dispersal was negligible. Conclusions : Our study highlights that under severe natural disturbance regimes, the effect of natural filters outweighed the negative effects of urban filters. However, the alteration of natural flooding processes by human activities is also a major mechanism influencing plant trait composition in urban riparian communities as forests subjected to reduced flood

This study aims to reconstruct the recent dynamics of two bogs located in an agricultural landscape and to determine which factors favour tree expansion, the most salient change recently reported in treeless peatlands. The vegetation and hydrological dynamics of the bogs as well as land use changes in the vicinity were reconstructed using a combination of paleoecological, paleohydrological, and historical approaches. It was hypothesized that upland deforestation indirectly induced atmospheric mineral dust deposition on sites, thus increasing nutrient availability and triggering forest expansion. Results indicated that a widespread, but asynchronous tree expansion occurred in both bogs during the 20th century. However, no evidence suggesting that nutrient enrichment favoured the phenomenon was found. Forest expansion seems rather to have been favoured by drying of the peat surface, as a decrease of the water table depth coincided with the beginning of the forest encroachment on both sites. This drying correlated with the establishment of an in situ artificial drainage ditch on one site and with agricultural development in the catchment of the other. Local historical factors of each site apparently override regional factors such as climate anomalies or upland deforestation in explaining rapid, abrupt changes in bogs.

Overabundant populations of large herbivores have strong persistent effects on forest composition, structure, and function. However, the mechanism through which plant communities recover their original composition and function after herbivore management remains poorly understood. We assessed the temporal trajectories of the herbaceous communities in Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss stands on Anticosti Island (Quebec, Canada) over 8 years following clear-cutting and deer management. The impact of deer exclusion or reduction to 7.5 and 15 deer·km–2 was compared with benchmark in situ deer densities (27 and 56 deer·km–2). Effects of deer management treatments on plant species and functional trait assemblages over time were assessed using principal response curves. Although complete deer exclusion seemed necessary to modify species composition from that occurring under intense browsing, a reduced density of 7.5 deer·km–2 was sufficient to induce significant changes in functional trait assemblages of regenerating stands. For instance, reduced deer densities favored plants with brightly colored flowers and compound inflorescences pollinated by animals and producing large seeds and fleshy fruits dispersed by animals. We conclude that the boreal forest's herbaceous communities are resilient to chronic browsing when deer population reduction and forest clearcutting are applied in synergy., Les populations surabondantes de grands herbivores ont des effets majeurs et persistants sur la composition, la structure et le fonctionnement de la forêt. Toutefois, le mécanisme par lequel les communautés végétales retrouvent leur composition et leur fonctionnement originels en réponse au contrôle des herbivores demeure mal compris. Nous avons évalué les trajectoires temporelles des communautés herbacées dans des peuplements d'Abies balsamea (L.) Mill. et de Picea glauca (Moench) Voss à l'île d'Anticosti (Québec, Canada) pendant 8 années après avoir effectué une coupe à blanc et contrôlé les populations de cerfs. L'impact de l'exclusion du cerf ou d'une réduction de la densité à 7,5 ou 15 cerfs·km–2 a été comparé à des densités témoins in situ (27 et 56 cerfs·km–2). Les effets des traitements de gestion du cerf sur les espèces végétales et les assemblages de traits fonctionnels ont été évalués en fonction du temps au moyen de la méthode des courbes de réponses principales. Bien que l'exclusion complète du cerf ait semblé nécessaire pour modifier la composition spécifique par rapport à celle observée en conditions de broutage intense, une densité réduite à 7,5 cerfs·km–2 était suffisante pour induire des changements significatifs dans les assemblages de traits fonctionnels des peuplements en régénération. À titre d'exemple, des densités réduites de cerfs ont favorisé les plantes à fleurs de couleur vive et les plantes à fleurs composées pollinisées par les animaux et produisant de grosses graines et des fruits charnus dispersés par les animaux. Nous concluons que les communautés herbacées de la forêt boréale sont résilientes au broutage chronique quand une réduction des populations de cerfs et une coupe forestière à blanc sont appliquées en synergie.

Indicator species have been used successfully for estimating ecosystem integrity, but comparative studies for defining optimal taxonomic group remain scarce. Furthermore, species combinations may constitute more integrative tools than single species indicators, but case studies are needed to test their efficiency. We used Indicator Species Analysis, which statistically determines the association of species to one or several groups of sites, to obtain indicators of ecosystem recovery after various deer density reductions. We used five taxonomic groups: plants, carabid beetles, bees, moths and songbirds. To test whether species combinations could complement single indicator species, we used plants as a model taxon and examined the indicator value of joint occurrence of two or three plant species. Our study relies on experimental controlled browsing enclosures established for six years on Anticosti Island (Quebec). Four levels of deer density (0, 7.5 and 15 deer km-2 and natural densities between 27 and 56 deer km-2) were studied in two vegetation cover types (uncut forests and cut-over areas), in a full factorial design for a total of eight experimental treatments. For all taxa but bees, we tested 54 treatment groups consisting in one specific density or in a sequence of two or more consecutive deer densities in one or both cover types (ten groups for bees, sampled only in cut-over areas). We found 12 plants, 11 moths and one songbird to be single species indicators of ecosystem conditions obtained under 12 different treatment groups. Six treatment groups were indicated by plants and six different ones by moths, of which one group was also identified by a songbird species. Moths were thus worth the extra sampling effort, especially since the groups they indicated were more treatment-specific (mainly one or two deer density treatments). We tested the same 54 treatment groups for plant species combinations represented by two or three co-occurring species. Plant combinat

PREMISE OF THE STUDY: Assessing seed quality in orchids has been hindered by stringent germination requirements. Seed quality has traditionally been assessed in orchids using in vitro or in situ germination protocols or viability staining. However, these methods are not always well suited for rapid assessment of viability in the context of ecological studies. METHODS: The potential of an ex situ protocol for seed viability assessment of orchids in ecological studies was investigated by sowing seeds of Platanthera blephariglottis on Sphagnum moss collected in the orchid's natural habitat. Ex situ germination results were compared with those obtained by viability staining using triphenyltetrazolium chloride (TTC), and the effect of seed testa color on staining and germination results was investigated. KEY RESULTS: The ex situ protocol yielded high germination rates, with 66% of the seeds germinating after 9 wk. Depending on the seed testa color class, ex situ germination rates were about 1.4 to 2.5 times higher than viability rates determined using TTC, indicating that the TTC technique underestimated viability compared with the method using ex situ germination. The TTC estimates of viability rates were higher for seeds with dark-colored testae than for pale ones, whereas seed testa color had no effect on germination. CONCLUSIONS: Our study showed promising results for the use of ex situ germination as an alternative to previously developed protocols for seed viability assessment of orchids in ecological studies. Staining using TTC might not be well suited for this purpose, since it introduced a bias with respect to seed testa color.

Questions : What vegetation changes occurred over three decades on two large temperate peatlands (1115 ha) isolated in an agricultural landscape and affected by a human-ignited fire? Location : Southwest Québec, Canada. Methods : In 2012, we revisited 103 plots first sampled in 1984–85. Changes in species composition were evaluated using the Sørensen dissimilarity index, in species frequency with Chi-square goodness-of-fit tests, and in species cover using one-sample t-tests. Tree encroachment was evaluated using aerial photographs and satellite imagery. We used linear discriminant analyses (LDA) and ANOVA to evaluate the impact of tree encroachment on species composition. Results : We found a floristic dissimilarity of 35% between 1984 and 1985 and 2012. Most species whose frequency and mean cover increased were peatland species, while most species with lower frequency and mean cover in 2012 were non-peatland species. The total area occupied by forest increased from 26% to 51%, an overall gain of 280 ha of forest. The species composition of old and new forests as well as of open sectors was highly distinct, as shown by the LDA that correctly assigned 97% of the sampling plots to these groups. Non-peatland species were 15 and five times more abundant than peatland species in old and new forests than open habitats, respectively. Conclusions : Gradual drying of the peatland margins due to drainage of the surrounding catchment, as well as post-fire succession are likely the main drivers of the changes observed. Overall, our study showed that peatlands isolated in an anthropogenic landscape are dynamic ecosystems where vegetation communities can experience substantial changes in a short time frame. The broader implication is that peatland conservation in highly modified landscapes must be linked to restoration.

Overabundant populations of large herbivores have strong persistent effects on forest composition, structure, and function. However, the mechanism through which plant communities recover their original composition and function after herbivore management remains poorly understood. We assessed the temporal trajectories of the herbaceous communities in Abies balsamea (L.) Mill. and Picea glauca (Moench) Voss stands on Anticosti Island (Quebec, Canada) over 8 years following clear-cutting and deer management. The impact of deer exclusion or reduction to 7.5 and 15 deer·km–2 was compared with benchmark in situ deer densities (27 and 56 deer·km–2). Effects of deer management treatments on plant species and functional trait assemblages over time were assessed using principal response curves. Although complete deer exclusion seemed necessary to modify species composition from that occurring under intense browsing, a reduced density of 7.5 deer·km–2 was sufficient to induce significant changes in functional trait assemblages of regenerating stands. For instance, reduced deer densities favored plants with brightly colored flowers and compound inflorescences pollinated by animals and producing large seeds and fleshy fruits dispersed by animals. We conclude that the boreal forest's herbaceous communities are resilient to chronic browsing when deer population reduction and forest clearcutting are applied in synergy., Les populations surabondantes de grands herbivores ont des effets majeurs et persistants sur la composition, la structure et le fonctionnement de la forêt. Toutefois, le mécanisme par lequel les communautés végétales retrouvent leur composition et leur fonctionnement originels en réponse au contrôle des herbivores demeure mal compris. Nous avons évalué les trajectoires temporelles des communautés herbacées dans des peuplements d'Abies balsamea (L.) Mill. et de Picea glauca (Moench) Voss à l'île d'Anticosti (Québec, Canada) pendant 8 années après avoir effectué une coupe à blanc et contrôlé les populations de cerfs. L'impact de l'exclusion du cerf ou d'une réduction de la densité à 7,5 ou 15 cerfs·km–2 a été comparé à des densités témoins in situ (27 et 56 cerfs·km–2). Les effets des traitements de gestion du cerf sur les espèces végétales et les assemblages de traits fonctionnels ont été évalués en fonction du temps au moyen de la méthode des courbes de réponses principales. Bien que l'exclusion complète du cerf ait semblé nécessaire pour modifier la composition spécifique par rapport à celle observée en conditions de broutage intense, une densité réduite à 7,5 cerfs·km–2 était suffisante pour induire des changements significatifs dans les assemblages de traits fonctionnels des peuplements en régénération. À titre d'exemple, des densités réduites de cerfs ont favorisé les plantes à fleurs de couleur vive et les plantes à fleurs composées pollinisées par les animaux et produisant de grosses graines et des fruits charnus dispersés par les animaux. Nous concluons que les communautés herbacées de la forêt boréale sont résilientes au broutage chronique quand une réduction des populations de cerfs et une coupe forestière à blanc sont appliquées en synergie.

Questions : What vegetation changes occurred over three decades on two large temperate peatlands (1115 ha) isolated in an agricultural landscape and affected by a human-ignited fire? Location : Southwest Québec, Canada. Methods : In 2012, we revisited 103 plots first sampled in 1984–85. Changes in species composition were evaluated using the Sørensen dissimilarity index, in species frequency with Chi-square goodness-of-fit tests, and in species cover using one-sample t-tests. Tree encroachment was evaluated using aerial photographs and satellite imagery. We used linear discriminant analyses (LDA) and ANOVA to evaluate the impact of tree encroachment on species composition. Results : We found a floristic dissimilarity of 35% between 1984 and 1985 and 2012. Most species whose frequency and mean cover increased were peatland species, while most species with lower frequency and mean cover in 2012 were non-peatland species. The total area occupied by forest increased from 26% to 51%, an overall gain of 280 ha of forest. The species composition of old and new forests as well as of open sectors was highly distinct, as shown by the LDA that correctly assigned 97% of the sampling plots to these groups. Non-peatland species were 15 and five times more abundant than peatland species in old and new forests than open habitats, respectively. Conclusions : Gradual drying of the peatland margins due to drainage of the surrounding catchment, as well as post-fire succession are likely the main drivers of the changes observed. Overall, our study showed that peatlands isolated in an anthropogenic landscape are dynamic ecosystems where vegetation communities can experience substantial changes in a short time frame. The broader implication is that peatland conservation in highly modified landscapes must be linked to restoration.

In areas where peatlands are abundant, they are likely to play a significant role in the hydrological and hydrogeological dynamics of a watershed. Although individual case studies are reported in the literature, there is a large range of aquifer–peatland interactions and there is a need to understand the controls of these interactions. The objectives of this study were (1) to better understand aquifer–peatland connections and how these may be predicted by geology and geomorphic location and (2) to provide a variety of reference sites for glacial geological settings. Slope and depression peatlands were studied in the Abitibi-Témiscamingue region and in the St. Lawrence Lowlands, two contrasting regions of southern Quebec. A total of 12 transects that span a shallow aquifer–peatland interface were instrumented with piezometers. Field investigations included peatland characterization, monthly water level monitoring, and continuous hydraulic head measurements with pressure transducers. The results indicate that 7 of the 12 transects receive groundwater from the surrounding shallow aquifer. At the peatland margin, four lateral flow patterns were identified and associated with slope peatlands (parallel inflow and divergent flow) and with depression peatlands (convergent flow and parallel outflow). Vertical hydraulic gradients suggest that water flows mainly downwards, i.e. from the peatland to the underlying mineral deposits. Vertical connectivity appears to decrease as the distance from the peatland margin increases. All of these exchanges are important components in the sustainability of peatland hydrogeological functions. The regional comparison of aquifer–peatland flow dynamics performed in this study provides a new set of referenced data for the assessment of aquifer–peatland connectivity.

Les tourbières jouent plusieurs rôles dans l’hydrologie de surface. Les liens hydrologiques entre les tourbières et les eaux souterraines (aquifères) demeurent toutefois peu connus, ce qui rend les zones d’interaction difficiles à identifier. Ce projet avait pour but d’identifier des espèces et des associations d’espèces floristiques indicatrices de zones d’échanges tourbière-aquifère. Ainsi, des suivis piézométriques et des inventaires floristiques ont été réalisés dans 9 tourbières situées dans le Centre-du-Québec et en Abitibi-Témiscamingue. Les échanges tourbière-aquifère ont été identifiés à l’aide de gradients de charges hydrauliques et les espèces indicatrices à l’aide de l’indice de valeur indicatrice INDVAL. Cette méthode a entre autres permis d’identifier 2 espèces (Carex limosa et Sphagnum russowii) et 4 associations d’espèces indicatrices d’un apport en eau souterraine à la tourbière. Les espèces indicatrices pourraient devenir un outil utile, rapide et peu coûteux pour prédire les zones d’interactions tourbière-aquifère et ainsi faciliter la tâche des gestionnaires du territoire.

Indicator species have been used successfully for estimating ecosystem integrity, but comparative studies for defining optimal taxonomic group remain scarce. Furthermore, species combinations may constitute more integrative tools than single species indicators, but case studies are needed to test their efficiency. We used Indicator Species Analysis, which statistically determines the association of species to one or several groups of sites, to obtain indicators of ecosystem recovery after various deer density reductions. We used five taxonomic groups: plants, carabid beetles, bees, moths and songbirds. To test whether species combinations could complement single indicator species, we used plants as a model taxon and examined the indicator value of joint occurrence of two or three plant species. Our study relies on experimental controlled browsing enclosures established for six years on Anticosti Island (Quebec). Four levels of deer density (0, 7.5 and 15 deer km-2 and natural densities between 27 and 56 deer km-2) were studied in two vegetation cover types (uncut forests and cut-over areas), in a full factorial design for a total of eight experimental treatments. For all taxa but bees, we tested 54 treatment groups consisting in one specific density or in a sequence of two or more consecutive deer densities in one or both cover types (ten groups for bees, sampled only in cut-over areas). We found 12 plants, 11 moths and one songbird to be single species indicators of ecosystem conditions obtained under 12 different treatment groups. Six treatment groups were indicated by plants and six different ones by moths, of which one group was also identified by a songbird species. Moths were thus worth the extra sampling effort, especially since the groups they indicated were more treatment-specific (mainly one or two deer density treatments). We tested the same 54 treatment groups for plant species combinations represented by two or three co-occurring species. Plant combinat

Les tourbières abondent dans l’ensemble du Québec, mais celles de la vallée du Saint-Laurent subissent des pressions anthropiques majeures. Ces pressions et les pertes de superficies en tourbières qui en résultent sont à peu près inconnues. Nous avons mesuré la superficie occupée par les tourbières en 1966 et 2010 dans la région de Bécancour et identifié les perturbations récentes qu’elles ont subies à l’aide de la photo-interprétation et de validations sur le terrain. En 2010, les tourbières couvraient 17 500 ha, soit 6,1 % du territoire étudié. De cette superficie, 10 485 ha représentaient des tourbières encore intactes et 7 015 ha des tourbières ayant subi des perturbations limitées, notamment par la présence de canaux de drainage et de chemins forestiers. Entre 1966 et 2010, 5 433 ha de tourbières (près du quart des tourbières présentes en 1966) ont subi des perturbations irréversibles, principalement en raison de la culture de la canneberge (Vaccinium macrocarpon). Cette culture a connu un développement important au cours de la dernière décennie dans le Centre-du-Québec.

Les écosystèmes sont naturellement adaptés pour faire face aux aléas du climat mais cette capacité est menacée par la rapidité des changements climatiques actuels. Les changements climatiques observés et anticipés sont considérés comme une grave menace à la biodiversité. Déjà connues comme ayant un statut précaire, les espèces vulnérables ou menacées sont d’autant plus sensibles à des modifications de leur habitat. L'exemple de la salamandre sombre des montagnes (Desmognathus ochrophaeus) au mont Covey Hill est typique de cette problématique. L'habitat de cette salamandre est intimement lié aux résurgences d’eau souterraine dont la dynamique hydrologique est contrôlée indirectement par le climat, par l’entremise de la recharge en eau souterraine. Toutefois, le contrôle qu'exercent les variables hydrologiques sur le maintien de cette population de salamandres est à peu près inconnu. Ces connaissances sont nécessaires pour définir des stratégies d'adaptation aux changements climatiques qui permettront de maintenir ou d'améliorer les chances de survie des espèces visées. Les études à l’échelle locale sont particulièrement cruciales dans ces environnements vulnérables situés près de la source des cours d'eau (zones amont ou headwater basins) qui jouent un rôle hydrologique et écosystémique majeur. Ce projet vise une application de la modélisation hydrologique et écologique sur le Laboratoire naturel du mont Covey Hill, un site d'environ 150 km2 instrumenté pour le suivi de variables hydrologiques et des populations de salamandres. La colline abrite la salamandre sombre des montagnes (Desmognathus ochrophaeus), une espèce désignée menacée, ainsi que la salamandre pourpre (Gyrinophilus porphyriticus), une espèce désignée vulnérable. L'objectif général est d'utiliser la modélisation hydrogéologique et écologique pour recommander des stratégies de conservation visant à promouvoir la résilience du milieu naturel du mont Covey Hill en présence de changements climatiques. L'an

La dépense parentale est la quantité de ressources qu'un parent investit dans les soins prodigués à ses rejetons. Chez les oiseaux, une grande part de la dépense maternelle est consacrée à la formation des oeufs : la taille de couvée et la masse des oeufs sont des variables importantes du succès reproducteur.La condition corporelle de la femelle (masse, taille, état de santé) ainsi que son âge peuvent avoir un effet sur la quantité de ressources qu'elle sera capable d'acquérir, alors que les variables environnementales, comme la structure du paysage environnant et les conditions météorologiques, déterminent l'abondance des ressources disponibles dans le milieu.La présente étude vise à déterminer l'impact de ces variables sur deux composantes de la dépense maternelle, soit la taille de ponte et la masse des oeufs, ainsi qu'à vérifier l'existence de compromis entre ces dernières. Pour ce faire, j'ai utilisé des données à long terme (2004-2011) sur la reproduction d'Hirondelle bicolore (Tachycineta bicolor) nichant dans un système de 400 nichoirs. Ceux-ci sont répartis sur un vaste territoire caractérisé par un gradient agricole, donnant lieu à une variation de la qualité de l'habitat. Les femelles les plus lourdes et les plus âgées sont celles qui avaient la plus grande dépense maternelle. Elles étaient capables de pondre un plus grand nombre d'oeufs de masse plus imposante.La structure du paysage agricole n'avait qu'un impact limité sur la dépense maternelle : la taille de couvée était plus petite dans les milieux où la proportion de cultures intensives (maïs, soya et céréales) était importante, mais la masse des oeufs n'était pas affectée par les cultures environnantes. Les femelles ont pondu des oeufs plus nombreux et plus gros lorsque les températures ressenties pendant leur formation étaient plus chaudes. Quant au compromis entre la taille de couvée et la masse des oeufs, j'ai pu le révéler en prenant en compte la condition corporelle de la femelle. Ainsi, les fe

Although ombrotrophic temperate peatlands are important ecosystems for maintaining biodiversity in eastern North America, the environmental factors influencing their flora are only partly understood. The relationships between plant species distribution and environmental factors were thus studied within the oldest temperate peatland of Québec. Plant assemblages were identified by cluster analysis while CCA was used to related vegetation gradients to environmental factors. Five assemblages were identified; three typical of open bog and two characterized by more minerotrophic vegetation. Thicker peat deposit was encounter underlying the bog assemblages while higher water table level and percentage of free surface water distinguished the minerotrophic assemblages. Overall, the floristic patterns observed were spatially structured along the margins and the expanse. The most important environmental factors explaining this spatial gradient were the percentage of free surface water and the highest water-table level.

La colline de Covey qui constitue une vaste zone de recharge pour l’aquifère régional se distingue par l’abondance et de la diversité des milieux naturels qu’elle abrite. Ces milieux se caractérisent, entre autres, par la présence de plusieurs ruisseaux et sources qui servent d’habitats à deux espèces de salamandres rares. L’alimentation en eau de ces sources est en partie assurée par la présence d’une tourbière naturelle située au sommet de la colline. Les principaux objectifs du projet étaient d’étudier la dynamique hydrologique et écologique passée et actuelle de la tourbière et de mettre en place un réseau d’instruments qui permettra l’étude de son fonctionnement futur. Les objectifs spécifiques du projet étaient 1) de caractériser les échanges hydriques entre la tourbière et le reste de la colline, 2) d’établir le bilan hydrique de la tourbière, 3) de déterminer les composantes de la tourbière les plus sensibles aux perturbations, 4) d’identifier les communautés végétales présentes et de reconstituer leur évolution dans le temps, et 5) d’identifier les variables environnementales expliquant la répartition spatiale et la composition des communautés végétales. Le projet a été réalisé en trois volets : hydrologie, écologie végétale et paléoécologie. Le bilan hydrique de la tourbière indique que l’apport d’eau provient de l’aquifère environnant (52-70 %) et des précipitations (30-48 %). Les sorties se font par évapotranspiration (38-44 %) et par les ruisseaux exutoires (56-62 %). La contribution de la tourbière à l’hydrologie de la colline provient principalement de l’écoulement dans la couche de surface (acrotelme) des dépôts tourbeux qui, grâce à sa conductivité hydraulique plus élevée, contribue à l’écoulement vers les ruisseaux exutoires. Les inventaires floristiques ont permis de démontrer le haut niveau d’intégrité écologique de la végétation de la tourbière et d’identifier cinq communautés végétales distinctes, dont trois d’appartenance ombrotrophe. Les prin

Le mont Covey Hill héberge la principale population de Salamandres sombres des montagnes (espèce menacée) connue au Canada ainsi qu'une population de Salamandres pourpres (espèce préoccupante). L’objectif à long terme du projet était de mieux comprendre la dynamique hydrique des habitats de ces salamandres afin d’identifier les actions nécessaires à leur protection et à leur survie. Les objectifs spécifiques étaient 1) de poursuivre la mise en place d’un réseau de suivi hydrologique sur le mont Covey Hill, 2) d’identifier le rôle des processus hydrologiques dans le maintien des habitats de salamandres, 3) de sensibiliser la population à l’importance de protéger ces habitats. Des stations de mesures ont été installées pour le suivi des cours d’eau (10), de la nappe (23) et des précipitations. Un suivi géochimique (pH, conductivité électrique et composition isotopique) a été réalisé par 14 échantillonnages d’eau sur l’ensemble des stations. Les propriétaires ont été invités à visiter le Laboratoire Naturel et à prendre connaissance de la problématique des habitats de salamandres menacées. Les résultats ont montré que l'eau souterraine est peu influencée par les précipitations. Les cours d’eau reçoivent toutefois de la nappe des volumes d'eau importants qui permettent de soutenir les débits d'étiage. Les stations ont un comportement hydrologique différent selon leur emplacement sur la colline, indiquant une variabilité spatiale dans la contribution du ruissellement et de l’infiltration. Des analyses plus détaillées ajouteront prochainement de nouveaux éléments à cette interprétation préliminaire. L'ensemble des résultats sera utilisé dans l’élaboration d’un protocole de suivi des populations de salamandres. Une base de données est en développement sur le site web du laboratoire Naturel pour rendre disponibles les résultats de l’étude. Un article de vulgarisation sera rédigé et les sites web du Laboratoire Naturel, de CNC et de la SCABRIC seront mis à jour (fin février

Overabundance of wild ungulates, especially exotic species, is a major threat to several ecosystems worldwide. While the response of forest vegetation to high density of herbivores has been well studied, far less is known about peatland vegetation. In this paper, we assessed the long term impact of white-tailed deer (Odocoileus virginianus) on plant communities of ombrotrophic (bog) and minerotrophic (fen) peatlands in eastern North America. Vegetation of five peatlands that have experienced high deer densities for at least 75 years was compared with that of five peatlands situated at proximity but on deer-free islands. We investigated deer impacts on plant species composition and cover, shrub height and cloudberry (Rubus chamaemorus) fruit/flower production and morphology. In bogs, white-tailed deer had no long term impact on plant species assemblages, but reduced lichen cover and increased sedges and grasses cover as well as the surface area of bare peat. On the other hand, the floristic composition of fens differed significantly between sites where deer were present or absent. Plant diversity was greater in undisturbed fens than in disturbed fens, especially for shrubs, sedges and liverworts. No detrimental effects of browsing on shrub height were observed. Conversely, deer browsing seemed to have deleterious impacts on cloudberry fruit/flower production as well as on the number of leaves per individual. Overall, our results suggest that white-tailed deer had some important impacts on the vegetation of peatlands that could be harmful for the long term conservation of peatland plant diversity