Habitat-related variation has been revealed in the seasonal reproductive patterns of great tits inhabiting mosaics of deciduous woodland fragments and managed coniferous forests. The number and quality of offspring tend to be higher in the non-preferred coniferous habitat compared with the preferred deciduous habitat. We explored whether these patterns can be explained by variation in food abundance and/or parental provisioning ability. Frass fall seemed not to be a reliable measure of the seasonal dynamics of nestling feeding conditions, although it is widely used for this purpose. No habitat-related differences were found in the tendency of parents to increase provisioning frequency in response to increased hunger levels of nestlings, suggesting that provisioning frequency as such is not a limiting factor for nestling growth. Higher feeding rates in deciduous habitat were associated with lower proportions of high-quality food items among prey delivered to offspring. These findings confirm that relatively high nestling feeding rates in birds may reflect the low quality of available food rather than the quality of parental care or an abundance of food in the environment. The results also indicate that deciduous forest habitat, though preferred by tits, may sometimes provide poorer brood-rearing conditions than the non-preferred, coniferous habitat. We suggest that the great tit's preference for deciduous habitat, which presumably evolved in more southern regions, may be maladaptive in northern regions where deciduous woods are mainly young, secondary stands of alder and birch.

Nomenclature: Tutin et al., 1993; Dickinson, 2003.

In order to focus efforts towards specific vegetation groups in fen restoration, knowledge of the peat-accumulating function of dominant fen species is critical. The decomposition rates of 3 species typical to undisturbed fens and 3 species that spontaneously colonize harvested fens were assessed. These species were incubated in both a restoration site (harvested fen) and an undisturbed fen to compare decomposition according to different environmental conditions. The average exponential decay coefficient (k) for all material types was slightly higher (circa 0.04·y^-1 higher) in the harvested fen than those observed in the undisturbed fen. However, the litter type (leaves, roots/rhizomes, or bryophyte fragments) had the largest impact on the decomposition rates. The 2 tested bryophytes had lower k-values (between 0.14 and 0.11 for Polytrichum strictum and 0.06 for Sphagnum centrale) than the vascular plant litter (between 0.25 and 0.50). The annual primary production of the tested species was also measured to estimate the peat-accumulating capacity of each species. Scirpus cyperinus had an annual primary production that was 3 times higher (1500 g·m^-2·y^-1) than the other species (between 300 and 550 g·m^-2·y^-1). Estimates show that the harvested fen has a high peat-accumulating potential due to the high biomass production observed at this site.

Nomenclature: Scoggan, 1978; Anderson, 1990; Anderson, Crum & Buck, 1990.

We examined 6 direct (i.e., based on tree ring counts) and 2 indirect (i.e., based on correlations between age and tree characteristics) methods to estimate the age of hollow trees. The errors associated with methods were compared by simulating rotten centres of different sizes (diameter: 5–82 cm) in tree ring cores from sound old oaks (Quercus robur) (diameter: 17–129 cm) collected from pastures in southeast Sweden. The lowest error (mean deviation: 15%) was obtained using tree ring data from the sampled hollow trees in combination with a function based on the growth pattern of sound trees. Indirect methods resulted in moderate errors (mean deviation was 23% and 26% for a function with bark crevice depth and with tree diameter, respectively). Because rotten centres often develop asymmetrically, we found it desirable to take a minimum of 2 cores from each hollow tree, from different cardinal directions. Trunks with a high probability of having a rotten centre could be identified before coring, as the width of the rotten centre increased with increasing bark crevice depth, with increasing size of any entrance hole, and with decreasing distance between the lowest entrance hole and the ground.

Nomenclature : Lid, 1985.

Sexual bimaturation, an intersexual difference in age at maturity, is a consequence of sexual size dimorphism (SSD). Sexual bimaturation arises through intersexual differences in growth trajectories. In theory, differences in growth trajectories should bias the operational sex ratio in favour of the early-maturing sex. In addition, in animals with sexual bimaturation, the late-maturing sex always maintains a lower intrinsic rate of growth (k) that may be linked to the metabolic cost of growth. We studied growth, its relation to the operational sex ratio, and its metabolic cost in the extremely size-dimorphic northern map turtle. We found that females take twice as long as males to reach maturity and that females maintain higher absolute rates of growth but have a lower k. The estimated operational sex ratio was even in our study population, and estimates of annual mortality were similar between adult males and females. Based on respirometry, we found no evidence that fast-growing females incur a metabolic cost compared to non-growing males.

Nomenclature: Le Sueur, 1817.

This study aims to evaluate the relative contribution to biodiversity of 4 dominant types of virgin black spruce (Picea mariana) forests found in a typical regional landscape of the black spruce—moss bioclimatic domain of central Québec: mature black spruce forests with a regular structure, old black spruce forests with a regular structure, old black spruce—fir (Abies balsamea) mixed forests with 2 stories, and mixed forests with irregular structure. A total of 16 stands covering these 4 forest types were sampled to characterize forest composition and structure as well as epixylic communities. Multivariate analyses of variance were performed to evaluate to what extent the epixylic community structure differed among the 4 forest types. Results show that the old two-story and irregular forest types sustain higher species richness of epixylics per unit area; therefore, these types may be key habitats for old-growth dependent species of bryophytes and lichens. The close association of epixylics with these forest types was mainly due to better moisture conditions and the presence of greater amounts of coarse woody debris in advanced decaying stages. We also demonstrated that forest compositional and structural attributes are good indicators of epixylic diversity. Finally, we suggest that maintaining old irregular black spruce—fir mixed forests should be the primary aim of conservation strategies for old-growth forests.

Nomenclature: Brodo et al., 2001; Ley & Crowe, 1999; Crum & Anderson, 1980.

The extent to which woody vegetation exhibits more expansive community structures and different relationships with environmental variables than herbaceous plants is poorly understood in savannas and barrens worldwide, especially those with shallow soils. We explored this question in oak barrens, which are savanna habitats characterized by shallow soils, in southern Ohio, USA. Groundcover plant aerial cover and environmental data were collected using 75 randomly located 1-m2 quadrats in 3 barrens. A combination of non-metric multidimensional scaling (NMDS) and β-flexible cluster analysis revealed 3 distinct herbaceous plant assemblages that varied in abundances of C₄ and C₃ graminoid species and several forbs. Herbaceous vegetation patterns were correlated with soil acidity, soil depth, plant available water, and especially soil organic matter and quadrat slope. By contrast, woody plants were more widely distributed than herbs, and woody vegetation patterns were strongly correlated only with soil organic matter, although they were weakly associated with quadrat slope and an index of tree influence. The expansion of woody plants into barrens is likely not restricted by most edaphic factors; thus, barrens are highly susceptible to woody plant encroachment that has been fostered by anthropogenic alterations to natural fire regimes (suppression, dormant season fires). We hypothesize that fires that are intended to mimic natural lightning fires during the growing season will be most effective in deterring woody plant encroachment.

Nomenclature: Gleason & Cronquist, 1991.

We examined the relationship between amphibian abundance and habitat features at 8 spatial scales in boreal Alberta, Canada. Twenty-three local pond variables and 15 landscape variables at 7 scales (50, 100, 200, 500, 1000, 2000, and 5000 m) were incorporated into a Principal Component Analysis (PCA) for each scale. We analyzed amphibian relative abundance against the PC axis scores using regression for each species and each scale. We found that each species' abundance was best described at different spatial scales. Wood frog (Lithobates sylvaticus) abundance was best predicted by local, pond-linked variables, boreal chorus frog (Pseudacris maculata) abundance by 1000-m-scale landscape variables, and western toad (Anaxyrus boreas) by the 100-m scale. We found significant positive relationships with amphibian relative abundance and dissolved oxygen, deciduous forest cover, mixed forest cover, and urban cover. Pond depth, conductivity, total dissolved solids, aquatic plant density, low-shrub cover, and conifer cover showed negative relationships with abundance. We also investigated relationships between landform type and amphibian relative abundance. All 3 species were most abundant on wetlands in the moraine landform. Our research highlights the importance of developing conservation plans based on knowledge of individual species' biology because amphibians do not all respond to the same spatial scale.

Nomenclature: Crother et al., 2000; Frost et al., 2006.

During the last century, the common reed (Phragmites australis) has spread through the North American continent following the introduction of a competitive Eurasian genotype. This invasion is problematic because marshes invaded by the common reed do not conserve a diverse flora and fauna. The southern part of the province of Quebec is also invaded by the common reed, but especially since the 1960s, i.e., since the beginning of the development of its highway system. There is very little information about landscape characteristics facilitating the establishment and spread of the common reed along roads. In this study, we mapped the common reed populations located along roads of a large region (1400 km²) of southern Quebec. Logistic regression models were performed to identify the main factors influencing the common reed. The road type is the most important variable of the models in agricultural or forest landscapes. Road ditches located on surface deposits with low drainage capacity (organic or clay) are more heavily invaded by the common reed than those located on rock, till or sand deposits. Consequently, a major road (national or regional) is more likely to be invaded by the common reed than a local road, especially if the road is located on organic or clay surface deposits. This study also shows that a large road receives more light energy than a narrow road, which favours a heliophilous plant like the common reed. The spread of the common reed along roads could be controlled by the use of shade structures (trees or shrubs planted along roads) which compete with the invasive plant for light.

Nomenclature : Marie-Victorin, 1995.

Habitat selection is the disproportionate use of available conditions and resources, and involves responses in space and time to perceived risks and rewards. It frequently depends on the scale of measurement, often in non-linear ways that preclude simple extrapolation across scales. More critically, animals often select different habitat components at different scales, and species vary in their scales of selection. Although multi-scaled research on habitat selection has proliferated, synthesis of this work has been impeded by imprecise terminology and arbitrarily defined analytical scales. Here, we review key concepts and findings and evaluate future prospects opened up in part by new technologies that enable novel and more efficient data collection. Innovative measurement, combined with novel analytical approaches, permits habitat selection to be investigated across a broad continuum of scales. By linking habitat selection to fitness as a function of scale, use-of-habitat assessments can be more effective. The fitness costs and benefits of habitat selection change with scale; the scales of habitat selection may inform us of limiting factors. We outline how reward/risk ratios can be used to assess the fitness implications of habitat selection across scales.

Predictions on displacement of suitable habitats due to climate change suggest that plant species with poor colonization ability may be unable to move fast enough to match forecasted climate-induced changes in habitat distribution. However, studies on early Holocene plant migration show fast migration of many plant species that are poor colonizers today. We hypothesize that warmer temperatures during the early Holocene yielded higher seed quality, contributing to explaining the fast migration. We studied how the 3 seed quality variables, seed mass, germinability, and requirements for break of seed dormancy, vary for seeds of 11 forest herb species with varying colonization capacity collected along a 1400-km latitudinal gradient. Within species, seed mass showed a positive correlation with latitude, whereas germinability was more positively correlated with temperature (growing degree hours obtained at time of seed collection). Only slow-colonizing species increased germinability with temperature, whereas only fast-colonizing species increased germinability with latitude. These interactions were only detectable when analyzing germinability of the seeds, even though this trait and seed mass were correlated. The requirement for dormancy break did not correlate with latitude or temperature. The results indicate that seed development of slow colonizers may be favoured by a warmer climate, which in turn may be important for their migration capacity.

Nomenclature: Tutin et al., 2001

We tested some responses of white spruce (Picea glauca) to fertilization, browsing, size of tree, and the season in which browsing took place. We collected leaf samples from trees that had been more or less fertilized and more or less browsed by snowshoe hares, for 9 y. We also used 3 levels of simulated browsing that removed approximately 10%, 30%, and 85% of all green biomass. We measured growth rate, camphor, and nitrogen concentrations in leaves, sampling monthly for 15 months. Camphor was induced by both natural browsing and clipping, and the response was influenced by plant resource status; camphor concentration increased with browsing pressure. At high browsing levels, both camphor concentration and growth rate declined. Seasonal camphor concentrations were highest in small trees that have a high risk of attack and during the winter, when trees are both slow growing and more heavily browsed.

Nomenclature : Cody, W. J., 2000.

Parasite-mediated selection in host populations is thought to vary in magnitude temporally. We monitored variation in life history traits that are known or suspected to influence fitness in a population of damselflies parasitized by larval water mites. Mite prevalence and intensity varied considerably over 5 y and was often higher in females. Prevalence and intensity were highest in the years when the damselfly emergence periods were early and of short duration, which also corresponded to damselflies emerging at larger sizes. Mites appeared to exert negative effects on apparent survival in some years only, and only for females, suggesting that parasite-mediated selection on damselflies is variable and dependent on other factors such as emergence times, weather, and sex and body size of hosts.

Nomenclature: Selys, 1862; Marshall, 1910.