Landscape homogenization resulting from high browsing pressure or forest management practices can impact plant and animal diversity. Large herbivores and logging may therefore influence small mammal populations, which are known to strongly respond to forest disturbances. We assessed the influence of white-tailed deer (Odocoileus virginianus) density and forest harvesting on deer mice (Peromyscus maniculatus) in the boreal forest of Anticosti Island (Quebec, Canada). We expected mice to be favoured by logging and thus that their abundance and body mass would increase in cutblocks, due to a greater availability of grasses providing food, shelter from predators, and improved thermoregulation. Mice may also benefit from an increase in deer density, especially at intermediate densities, where food (insects and seeds) availability is the highest. In 2 consecutive summers, we live-captured mice within a large, controlled deer browsing experiment where deer were maintained at 4 different densities (0, 7.5, and 15 deer km^-2 and ambient density, 27 to 56 deer km^-2) in forest and in cutblocks. We found higher mice abundance in logged habitat regardless of deer density, but body mass was unaffected by deer density and forest harvesting. While plant, insect, and bird communities have all been shown to respond to deer density reduction, the interspecific relationships between deer and mice appear neutral in this system.

Investigating the single and interactive effects of the main components of climate change (higher temperature, elevated CO₂, and water stress) on plants is crucial to our understanding of plant performance under future climate. We studied the effects of these factors on black knapweed (Centaurea nigra). Plants were grown under 2 temperature regimes (22/18 °C and 28/24 °C), 2 CO₂ concentrations (380 and 760 µmol·mol^-1), and 2 watering regimes (well watered and water stressed) in growth chambers, and their growth and physiological parameters, including biomass, growth indices, chlorophyll fluorescence, photosynthetic pigments, and ethylene evolution, were measured. We found that interactions among the 3 components of climate change primarily affected shoot and total biomass and specific leaf mass. Overall, higher temperature and water stress have negative effects, whereas elevated CO₂ has positive effects on C. nigra. Nevertheless, the negative effects of higher temperature and water stress stimulate adaptive responses by this species. Also, elevated CO₂ mitigates some of the adverse effects of these stress factors and regulates the plant's adaptive mechanism. It is likely that invasive weeds such as C. nigra have the potential to take advantage of climate changes, becoming more competitive and possibly posing significant challenges to maintaining indigenous biodiversity in the future.

Nomenclature: Kartesz, 1994; Darbyshire, 2003.

Dwarf bamboos are major understory plants in subalpine and temperate forests of Japan. Several microphysical factors are known to influence their coarse-scale distribution, including slope angle, convexity, and proportion of gravel on the soil surface (hereafter gravel cover), but the effects of these factors on local variations in distribution are unclear. To elucidate these effects we examined relationships between local variations in Sasa palmata distribution and the 3 mentioned microphysical environmental factors within a 20- × 20-m plot divided into 0.5- × 0.5-m quadrats in a cool-temperate deciduous broadleaf forest, applying intrinsic conditional autoregressive models at 3 spatial resolutions (0.5 × 0.5 m, 1.0 × 1.0 m, and 2.0 × 2.0 m). The models show that the 3 microphysical factors, known to affect the distribution of S. palmata at coarser scales, also affect its distribution at fine scales. Slope angle and gravel cover had negative effects, while convexity had positive effects on its abundance. However, the strength of their effects depended on the spatial resolution: convexity had the strongest effects at 2-m scale, while slope angle and gravel cover had stronger effects at the finer scales. These findings provide indications of scale-dependent effects of environmental factors that may contribute both to fundamental understanding of forest dynamics and to efforts to enhance the regeneration and conservation of target species.

Population genetics approaches are becoming widely used to assess the propagation potential of wildlife diseases. Such studies are often conducted on uninfected hosts because acute zoonotic diseases pose significant health risks to humans and infected hosts are thus more difficult to obtain. Predictions of disease spread potential assume that infected and uninfected individuals exhibit similar movement behaviours and genotypes. However, some diseases, such as rabies, might enhance individual's dispersal behaviour. Thus, if rabid animals are mostly long-distance migrants, prediction of rabies spread potential based on genetic analyses of uninfected animals might be misleading. Here, we genotyped 84 rabid and 113 nonrabid raccoons (Procyon lotor) to assess whether a difference in genetic structure pattern could be detected between these groups in a rabies epizootic area in southern Quebec, Canada. We also assessed whether genetic diversity differs among rabid and nonrabid raccoons by comparing expected heterozygosity, allelic richness, and inbreeding coefficient of the 2 groups. Finally, we tested for possible associations between rabies infection and microsatellite genotypes. We found no evidence of genetic structuring and no difference in genetic diversity among nonrabid and rabid raccoons. We also have limited evidence for a link between genotype and infection status. Our results thus suggest that the genetic structure of nonrabid raccoons is representative of that found in infected individuals and is thus effective to infer rabies propagation patterns in the wild.

During the twentieth century, populations of several deer species (Cervidae) increased dramatically in temperate and boreal forests worldwide, leading to major changes in forest plant and animal communities. The effect of deer overabundance on understory vegetation has been documented repeatedly. In situations of severe browsing pressure, even the least palatable vascular plants were negatively affected. However, deer impact on bryophytes has been greatly under-investigated despite their key role in ecosystem functioning and their high conservation profile. Taking advantage of a unique situation involving adjacent islands with and without deer that resulted from the introduction of black-tailed deer (Odocoileus hemionus) to the Haida Gwaii archipelago (British Columbia, Canada) we explored the response of the bryophyte community to unregulated browsing. We compared species density, cover, and diversity between small islands never colonized by deer and small islands with prolonged deer presence. We took a novel approach that combined direct observations of deer foraging with sampling of their impact on the vegetation. We show that even in situations of severe browsing pressure deer totally avoided bryophytes. Contrary to what is observed for vascular plants (even for tolerant species such as graminoids), species density, cover, and diversity of bryophytes were higher on the islands with deer. We attribute this pattern of higher bryophyte prevalence to reduced competition with vascular plants, especially for light.

Nomenclature: Vitt, Marsh & Bovey, 1988; Flora of North America, 1993.

Coastal sand dune ecosystems are known to be structured by disturbance along coast-to-inland gradients, but little is known about how such patterns might change on exposed islands where environmental gradients vector in multiple directions. We investigated responses in plant assemblages on Sable Island, a long (49 km) and narrow (1.25 km at the centre) mostly vegetated sand bar located 160 km off the east coast of Nova Scotia, Canada. We sampled vegetation composition across the island using a stratified random design to capture a range of environmental predictors potentially associated with substrate conditions and disturbance from coastal processes, as well as grazing by the island's feral horses. We identified 3 different vegetation assemblages using hierarchical cluster analysis and non-metric multidimensional scaling that were associated with predictor variables. Distance from shore (both north and south shore) and slope angle were strongly related to both vegetation distribution and community composition. Areas farther from shore (subject to less wind and wave disturbance) contained greater amounts of shrub and heath vegetation. However, all parts of the island contained non-vegetated areas or stress-tolerant plant communities. Patterns of vegetation succession inferred for Sable Island were not linear and are better described as responses to repeated environmental disturbance rather than to a gradual process of soil development and competitive displacement. In addition to highlighting the multi-directional environmental influences on community composition of island systems, our results establish baseline spatial information on vegetation communities necessary for the ecological monitoring of Sable Island as a new National Park Reserve.

While diverse, native riparian vegetation provides important functions, it remains unclear to what extent these assemblages can persist in urban areas, and under what conditions. We characterized forested riparian vegetation communities across an urbanizing metropolitan area and examined their relationships with surrounding land cover. We hypothesized that native and hydrophilic species assemblages would correlate with forest cover in the landscape. For each of 30 sites in the Portland-Vancouver metro area, we recorded vegetation at 1-cm intervals along 3 transects using the line-intercept method. Land cover was characterized at 2 scales: within 500 m of each site and across the entire watershed. Multivariate analyses were used to evaluate relationships between species composition and land cover patterns. A classification tree was created to determine landscape predictors of riparian community type. Results indicated a strong relationship between watershed land cover and vegetation diversity and structural complexity. Our hypothesis of native species association with landscape forest cover in urban riparian areas was supported, but we found no clear relationship between land cover and wetland indicator status. Our results suggest that high watershed forest cover (at least 15%) may enable the persistence of functionally diverse, native riparian vegetation communities in urban landscapes.

Nomenclature: Hitchcock & Cronquist, 1973; USDA NRCS, 2013.

Habitat for American martens (Martes americana) is associated with forest types that offer fine-scale structural complexity in part used to access the winter subnivean environment, which is used for food procurement, predator avoidance, and rest. We assessed habitat characteristics associated with points of subnivean access by martens from winter tracking in a boreal mixedwood forest in northern Ontario. We then assessed areas designated as reserved marten habitat according to Forest Management Guidelines for the Provision of Marten Habitat in Ontario with respect to these characteristics. Coarse woody debris counts were positively associated with subnivean access. We found some evidence that subnivean access points differed in a transition from patches of coniferous to mixedwood forest, defined by tree basal area. Especially in mixedwood patches, deciduous shrub density may also facilitate subnivean access. Development of guidelines to protect features associated with fine-scale structural complexity important in winter to martens should be a research priority.

Nomenclature: Flora of North America Editorial Committee, 1993; Wilson & Reeder, 1993.

Brown-water dystrophic lakes have several limnological characteristics that clearly separate them from clear-water oligotrophic and murky eutrophic lakes. In this study, I examined the sedimentary midge (Nematocera) assemblages from 30 shallow boreal lakes of varying humic status to test the influence of dystrophy on community composition. The results indicate differing community assemblages between oligohumic and humic lakes. Several taxa were restricted to clear-water lakes, whereas dystrophic lakes also had their characteristic taxa, which were rare or absent in the clear-water lakes. The most common and abundant nematocerans having statistically significant indicator values for dystrophy were chironomids Zalutschia zalutschicola-type, Tanytarsus mendax-type, and Cladotanytarsus mancus-type, together with the phantom midge Chaoborus flavicans. These results indicate that the level of dystrophy plays a significant role in determining midge distribution in boreal lakes. Therefore, consideration of differences in humic conditions is crucial to contemporary midgebased environmental assessments and long-term paleolimnological investigations, because temporal changes in the humic state may have occurred.

Boreal wetlands are recognized as important wildlife habitats, especially as breeding and staging grounds for a large number of waterfowl. The main objectives of this study were to quantify the distribution of wetland and aquatic wildlife-habitat landscape types within boreal Quebec and to determine how such recognizable wildlife habitats vary among climatic regimes and landforms. A total of 456 forest maps systematically distributed within a 540000 km² area were used to classify 12 wetland and 5 different aquatic habitat types. Habitat types belonging to wetland and aquatic classes respectively covered 10.3 % and 11.7 % of the study area. Spatial heterogeneity was confirmed using a hierarchical cluster analysis by identification of 6 wetland landscape types further categorized into 3 groups: wet, dry, and anthropogenic. The last emphasizes the magnitude of human alteration of aquatic habitats, with reservoirs representing 26% of total water coverage. Partial redundancy analyses showed that landform data alone had better explanatory power (28%) than climatic data (19%) to account for the variation in wetland coverage. These results suggest that terrestrial ecozones based on landform (rather than climate) could serve as indicators for wetland conservation planning and facilitate wetland conservation and management decisions.