Prey animals use different strategies to avoid detection by predators and to flee once detected. Key issues are what aspects of movement prey change in response to predation risk and how differences in habitat affect escape movements. We answer these questions for snowshoe hares (Lepus americanus) in Montana, using an experimental manipulation and habitats for which annual mortality rates varied more than fourfold. We examine a) whether the mortality risk of a habitat affects movement tortuosity and speed of foraging snowshoe hares and b) whether tortuosity and speed of hares fleeing from a predator (a leashed dog, Canis familiaris) differ among these forest stands. Snowshoe hares did not differ in tortuosity or speed while foraging in these stands, suggesting that other anti-predator behaviours were used. Hares fleeing from the leashed dog showed much faster and straighter movements than foraging hares, but escape trajectories were similar in all forest stands, suggesting a relatively inflexible response while fleeing. Varying tortuosity and speed are clearly part of the snowshoe hare's behavioural repertoire for escaping predation, but these attributes of movement were insensitive to the annual mortality rates in each forest stand.

Urbanization results in ecosystem fragmentation, habitat loss, and altered environmental conditions that usually favour pioneer and ruderal species. The objective of this study was to evaluate the impact of urban conditions on liana abundance in temperate forests. Fieldwork was conducted in 50 forests of the metropolitan Montréal area (Quebec, Canada) and focused on the 6 most common lianas of the study area, Celastrus scandens, Menispermum canadense, Parthenocissus quinquefolia, Solanum dulcamara, Toxicodendron radicans, and Vitis riparia. Potential drivers of liana distribution at the landscape scale (e.g., surrounding land use, urban heat island) were quantified based on satellite images and land use maps. At the forest scale, we investigated biotic and abiotic variables in 429 sampling plots. We found that at the landscape scale, lianas benefited from urbanization, mainly through warm microclimates created by urban heat islands (UHI) as lianas are not well adapted to cold climates. At the forest scale, lianas were more abundant in disturbed forests and in edge habitats than in less disturbed forest and core habitats. Their fast growth rate enables them to quickly take advantage of high light availability on disturbed sites. Our results suggest that urbanization and ongoing climate changes will lead to an increase in liana abundance in temperate forests.

Plants have evolved a wide range of adaptation mechanisms that enable them to grow and develop in environments of high soil salinity. We examine the plant—microbial interactions of Salicornia europaea (Herbaceae) as potential mechanisms responsible for the high tolerance of halophytes to saline conditions. We evaluated the impact of different NaCl concentrations on microorganisms associated with S. europaea growing at 2 saline sites in central Poland: a salty meadow in the vicinity of a soda factory (anthropogenic salinity) and an area affected by natural brine (landscape park). The community-level physiological profiles of microorganisms associated with the plant were determined for endophytes from the roots, rhizosphere, and salt-affected soil. The highest total microbial metabolic activity, irrespective of the test site, was always in the rhizosphere, while the activity of endophytic and soil populations depended on salinity. In general, a higher total metabolic activity was observed at the test site exhibiting higher salt concentration. We propose that increased metabolic activity of microbial populations under increased salt stress can significantly contribute to the site adaptation of halophytes to saline conditions.

Successful management of boreal forests requires an understanding of the scales at which focal species use resources in their environment. Fine-resolution, within-home-range habitat selection by American martens (Martes americana) has not been well studied in boreal forests, although the importance of downed wood seems almost universal for hunting and resting in winter. We examined winter habitat selection by radio-collared martens while the population was at a 5 y low near Kapuskasing, Ontario, Canada. Fine-resolution models were developed using habitat data collected from snow-tracking 5 resident martens. Resource selection models were compared using an information theoretic approach, and model performance was evaluated by the ability of the models to correctly classify resource use events by martens. Our models suggest that martens selected locations within home ranges that had higher subnivean access to large coarse woody debris (CWD), a medium density of large conifers, and a higher proportion of eastern white cedar (Thuja occidentalis) trees compared to random sites within the home ranges. Subnivean access to CWD decreased with increasing snow depth, and sites used by martens had consistently higher access to CWD compared to random sites within home ranges across the entire range of snow depths measured. Areas used by martens also had lower snow depth than the average within home ranges. Our study illustrates how fine-resolution data can increase the predictability of resource use by martens, and suggests that incorporating sub-stand-level measures such as conserving patches of white cedar and ensuring that CWD remains high through forest succession can increase our ability to successfully manage boreal forests for species such as marten that prefer older stands.

Exotic vascular plants are increasingly numerous, and decision support systems identifying the most problematic species are needed to help environmental managers to develop control strategies. The fundamental tool in this respect is a list of weeds, or a weed risk assessment. We propose here a list for the province of Quebec constructed using an innovative approach based on 1) well-defined criteria, 2) consideration of all potential problems associated with exotic plants, 3) use of credible scientific data, 4) assessment by a panel composed of experts with diverse expertise and who are also potential users of the list, 5) use of a decision support approach, and 6) a debate among experts in order to reach a verdict concerning the status (weed, no weed) of each candidate plant. The list contains 87 of the 908 taxa of exotic vascular plants that are naturalized in Quebec, i.e., 9.6% of the total. About two thirds of the weeds are problematic for agricultural or ornamental plant production or for forestry; the others are, in decreasing numerical order, problematic for biodiversity or natural ecosystem functions, health, landscaping or home gardening, and recreational activities. Evaluating the threat posed to biodiversity by individual species was a challenge, because few relevant studies have been published. The use of well-defined criteria greatly reduced (by a factor of 3) the number of weed species from an initial list based on individual uncensored expert opinions. The resulting list is not definitive, and should be used with caution. However, we estimate that our approach is more rigorous than the other qualitative approaches developed to date, with performance that matches the semi-quantitative or quantitative tools frequently used for assessing invasive plants, such as the Australian Weed Risk Assessment.

Late spring frost disturbances have significant ecological and physiological impacts on forests. Frost-induced cambial damage that occurs when cells are actively dividing can result in the formation of frost rings, abnormal modifications to wood anatomy within the annual growth rings of an injured tree. Frost rings are indicators of growing season frost damage to the cambium and therefore have potential to be used both as a proxy in the reconstruction of extreme climatic events and to identify frost-prone environmental conditions. In this study, we measured the occurrence of earlywood frost rings across cambial age and diameter class in 11 jack pine (Pinus banksiana) populations of northern lower Michigan. Earlywood frost ring formation was greater in younger trees and in trees with smaller diameters. Biotic (cambial age, diameter, and ring width) and abiotic (elevation, initial site-related growth rate, and minimum temperature) factors demonstrated significant influence on the probability of earlywood frost ring formation. When using frost rings as a proxy of historical climate, susceptibility to abrupt freezing temperatures during the growing season and thus the ability of an individual tree to record a frost disturbance should be considered.

One of the most important factors influencing breeding success in many bird species is predation. Nest site choice is one way of lowering the probability of such losses. In an agricultural landscape of eastern Poland, we examined the relationship between red-backed shrike (Lanius collurio) nest site characteristics, i.e., height above ground, concealment, and occurrence of thorns, and the risk of nest predation. We also considered the relationship with distance to potential predators, i.e., corvid nests, and the distance to buildings. Our results showed that only 1 environmental factor significantly influenced breeding success. Birds nesting closer to buildings achieved higher breeding success than those more distant from buildings. A positive correlation between date of first egg laying and distance from the nest to the buildings was also found. These results indicate that areas with human activities and buildings can created habitats that improve breeding success for some species. On the other hand, the growth of such habitats also contributes to decreasing availability of semi-natural areas for breeding and foraging for these species.

Forests dominated by the endangered tree species whitebark pine (Pinus albicaulis) are threatened by multiple stresses (fire suppression, climate change) and disturbances (white pine blister rust [Cronartium ribicola], mountain pine beetle [Dendroctonus ponderosae]). To gain insight into how these ecosystems respond, we quantified vegetation change over 2 decades (21–29 y) in xeric and submesic P. albicaulis ecosystems near the northern edge of the species' range on the leeward side of the Coast Mountains of British Columbia, Canada. We compared changes in overstory and understory vegetation composition of these stands to changes in mesic, non-whitebark pine ecosystems in the same region. Multi-response permutation procedure (MRPP) analysis showed that the overstory of xeric whitebark pine ecosystems became compositionally similar to mesic ecosystems, i.e., there was increased dominance by Abies lasiocarpa or Tsuga mertensiana. Yet understory composition in xeric whitebark pine stands changed little and there was continued regeneration of P. albicaulis. Submesic whitebark pine stands developed a dense canopy dominated by T. mertensiana, and although their understories did not become compositionally similar to mesic ecosystems, there was minimal P. albicaulis regeneration. Understory stability in xeric and submesic whitebark pine ecosystems over 21–29 y suggests compositional resilience in these ecosystems to multiple stresses and disturbances. However, ongoing disturbance affecting both overstory and understory P. albicaulis might still result in the loss of this keystone species.