An experimental restoration in Wisconsin planted in 1986 tested the hypothesis that growing-season fire maintained richness of native herbaceous dicots (forbs). Replicated plantings were burned in May or July, or left unburned, every third year from 1989 to 2004 and monitored for differences in cover and richness through 2006. Native forb richness was higher in burned than unburned plots, with greatest richness following July burns. Two seasons after the 2004 fires, counts averaged 2 more native forb species in replicates burned in July than those burned in May and 4 more species in replicates burned in July than those left unburned. The strongest statistical response to fire season was higher richness of early-flowering species in replicates burned in July, largely attributable to early-flowering forbs planted in 1986 that persisted better after July burns than in other treatments. Spring fire increased cover of late-flowering C₄ grasses. As of 2006, C₄ grasses accounted for 76% cover after May fires, 52% after July fires, and 39% in unburned plots. Replicates burned in July held more alien species for the first 12 y, after which alien richness declined and differences among treatments disappeared. Summer fire best maintained richness of native, especially early-flowering, species.

Forest stands within the Quebec—Ontario paludification-prone Clay Belt are expected to converge to open unproductive black spruce (Picea mariana) stands regardless of initial tree composition with the prolonged absence of fire. We hypothesized that different surface deposits would display different stand transition characteristics, as recent research on the deglaciation history of the regions suggests that certain site conditions could exhibit different susceptibility to paludification. We quantified the rate and age of transitions of different succession stages for various surface deposits using a large spatio-temporal forest database. Our results suggest that a complete convergence to open and less productive black spruce stands can occur, but it may take a long time (i.e., more than 500 y), especially on surface deposits less prone to paludification, such as coarse-textured soils. We also observed that if succession pathways start with open and less productive black spruce stands, their capacity to change to more productive stands is conditioned by the surface deposit. Consequently, based on preferential age of transition, transition rates, and succession pathways, we suggest an increased susceptibility to paludification as one goes from coarse-textured deposits to fine-textured deposits and finally to restructured clay deposits, which are regionally designated as Cochrane Till. In terms of forest management, surface deposit susceptibility to paludification should be taken into account in order to minimize soil organic accumulation and the loss of tree productivity.

Many species use behavioural thermoregulation to cope with changes in their thermal environment. Most studies to date, however, have focused either on ectotherms or on endotherms living in warm environments. Here we used heated taxidermic mounts to characterize microclimates available to North American porcupines during the cold Canadian winter. We then examined activity patterns and microhabitat use of wild individuals to test whether porcupines responded behaviourally to changes in thermal conditions. Dens offered good protection against the cold, and porcupines modified their use of dens as thermal conditions became more constraining. They reduced time spent outside of dens, increased the number of activity bouts in a day, and became more diurnal. When outside of dens, they fed more often, but did not change their use of microhabitats as thermal conditions became most constraining. Microhabitats other than dens were less predictable in the protection they offered against cold temperatures. This may be why porcupines based their behavioural thermoregulation strategy on modulating patterns of den use rather than on selecting warmer microclimates when outside of the den. We hypothesize that selection of microhabitats outside of the den was driven by food acquisition or predation risk.

Bird species are adapted to certain ranges of physical conditions and will respond to environmental heterogeneity depending on their ability to exploit a broad range of resources and their tolerance to new environmental conditions. We used the rufous-collared sparrow as a model to explore how the abundance of generalist passerine birds may vary along environmental gradients in the southern Neotropics. We analyzed variations in the abundance along 6 gradients expressing variations in climate, productivity, the proportion of native forest in the landscape, the proportion of vegetation types through the transition between regions, and the intensity of human activities (agriculture, urbanization). The rufous-collared sparrow was most abundant in seasonal and semi-arid climates. Thermal amplitude was the best climatic predictor of the species abundance at the large scale. Within regions where climatic conditions are relatively homogeneous, land use better predicted abundance patterns. The species responded positively to increasing primary productivity, agricultural intensity, and native forest degradation and conversion and negatively to increasing urbanization. The rufous-collared sparrow adapts successfully to new environments created by human activities such as agriculture, ranching, forestry, and urbanization. Some native species may be tolerant to certain types and intensity of human activities, and knowledge of how they respond to both natural and human-created environments may help efforts to anticipate the impact of human activities on native birds in a changing world.

It is not well understood why successful regeneration of balsam fir and paper birch was observed in the south-central portion of Anticosti Island, despite a high-density deer population reputed to severely browse the seedlings of these 2 species. The area where this regeneration occurred was severely affected by a hemlock looper epidemic in the early 1970s and was specifically confined to one geologic formation (Chicotte). We tested whether or not the occurrence of balsam fir and paper birch coincided with a certain range of soil properties (pH, exchangeable cations, soil depth, clay content, and forest floor thickness). Out of 49 plots surveyed, balsam fir and paper birch respectively occurred on 30 and 25 plots, while black or white spruce occurred on all plots. There was co-occurrence of balsam fir and paper birch in 15 plots in which the relative abundance of paper birch was low. Multivariate regression trees (MRT) indicated that balsam fir occurred on shallow soils, whereas paper birch occurred on deep soils. On shallow soils, MRT indicated better regeneration of balsam fir in soils with low clay content. Results suggest 2 concurrent mechanisms related to site fertility leading to the regeneration of balsam fir and paper birch. The first involves low fertility conditions that stimulate balsam fir to produce higher concentrations of anti-herbivore compounds. The second mechanism involves increased tolerance of birch saplings to repeated deer browsing on the deeper and more fertile soils. Future research should strive to confirm these mechanisms and understand why they were efficient on the Chicotte formation but not elsewhere on the island.

The distribution of exotic species bearing fruits may depend in part on their palatability to birds, because species attracting a more diverse array of dispersers should broadcast seed to a wider range of habitats, including those otherwise assumed to represent refuges from exotic species invasion, such as small islands. To test these ideas, we compared the palatability of 11 exotic shrub species to their occurrence on 91 islands of varying size and isolation in the Gulf Islands of British Columbia, Canada and the San Juan Islands of Washington, USA. The estimated palatability of fruits for 10 common frugivorous birds was positively related to the number of islands on which they occurred. Rubus armeniacus and R. laciniatus were the most widely consumed exotic species and the only such species prevalent on small islands, suggesting that they have benefited by attracting a wide array of frugivores that have, in turn, facilitated their rapid colonization of the region. Our results suggest that protecting small islands from human visitation will be insufficient to prevent exotic species establishment and the loss of native biodiversity.

This study examined the interactive effects of early and late season herbivory on the growth and reproductive output of figwort (Scrophularia nodosa). The early season herbivore is a pentatomid bug that feeds on and kills the apical meristem, while the late season herbivores are 2 weevil species and a sawfly that all feed on leaves and flowers. The direct effect of early season meristem damage on plant reproduction was quite limited, although meristem damage did cause increased branching. This change in plant morphology may entail that early season herbivores have profound indirect effects on plant reproduction by affecting the abundance of and damage caused by late season herbivores. Comparisons of plants with and without early season meristem damage, natural and artificial, also suggest that plants with meristem damage are significantly shorter throughout most of the summer and receive less damage late in season. However, the reduced damage translated to increased flowering but not to increased fruit production, suggesting that the plants were able to compensate for late season damage. In the end, and despite damage, figwort was well able to tolerate the observed meristem and leaf damage.

The present study investigates potential differences in trait plasticity as an additional contributing mechanism explaining ericaceous shrub dominance during different periods after logging. Two ericaceous species (Kalmia angustifolia, Rhododendron groenlandicum), and black spruce plants (Picea mariana), were submitted to combinations of 3 light levels and 2 levels of nitrogen addition during a simulated growing season of 9 weeks under greenhouse conditions. Plant traits related to light (photosynthesis, leaf mass per unit of area, leaf and aboveground biomass allocation, foliar N concentration) and nutrient acquisition (root mass ratio, specific absorption ratio, absorption of ¹⁵N) were measured in response to the manipulation of these resources. The leaf mass per unit of area (LMA) of both ericaceous species was significantly reduced by shading; LMA of Rhododendron and Kalmia was, respectively, 54% and 31% higher in the highest light treatment. The LMA of black spruce was unchanged in response to light level. There were few differences among species in trait response to N addition. Black spruce was characterized by higher nutrient absorption rate and specific absorption rate at higher N levels compared to the 2 ericads. With the exception of LMA, plasticity to light was higher for Kalmia; in contrast, plasticity to N addition was higher for Rhododendron and black spruce. Finally, LMA appears to be a key trait explaining the competitive advantage of ericaceous species (especially Rhododendron) and potential encroachment on forested sites after disturbance.

There is evidence that broad-scale species richness patterns of woody plants correlate with contemporary gradients of environmental energy inputs and water availability. However, climate-richness relationships for herbaceous species are less well known. Here we analyze the seed-bearing flora of Great Britain, quantifying the relationships between total, herb, and woody plant species richness and 14 environmental predictors measuring levels of energy, water, or combined energy and water. PCAs of the environmental variables identified the primary trends of environmental variation across Great Britain related to mean annual temperature and annual precipitation. OLS multiple regression and partial regression analyses identified mean annual temperature as the strongest driver of richness for all species groups. Similarly, reparameterized versions of published energy—water models for woody plant species richness and for angiosperm family richness gradients also identified energy variables as the primary predictors of the richness of all, woody, and herb species.

The rusty blackbird (Euphagus carolinus) has received much attention during the last decade, in part due to drastic population declines. We analyzed data from 15 y of fall migration monitoring at the Observatoire d'oiseaux de Tadoussac (OOT), located at the mouth of the Saguenay River on the north shore of the St. Lawrence River estuary in Quebec, Canada. The trend observed suggest an ongoing decline. Numbers of rusty blackbirds varied considerably between years, with peak movements occurring at 5-y intervals and possibly reflecting high reproductive success for those years. The numbers of adult boreal owls caught and banded at the OOT, and the proportion of juveniles, were negatively and positively correlated with rusty blackbird numbers, respectively. Peaks in rusty blackbird abundance occurred when red-backed voles (Clethrionomys gapperi) were abundant in the eastern boreal forest. Also, rusty blackbird numbers were positively correlated to the annual and winter North Atlantic Oscillation (NAO) indices and negatively to the combined precipitation for June, July, and August, suggesting that environmental factors may have contributed both directly and indirectly (through food web processes) to the cyclic variations in abundance observed. Current declines may be exacerbated by NAO fluctuation patterns, that is, more frequent negative indices may negatively affect reproductive success and possibly winter survival.