by Claire Morin | 10 April 2020
Published in Environmental Reviews 26(2): 113-120. https://doi.org/10.1139/er-2017-0066
Exotic species invasions are among the most significant global-scale problems caused by human activities. They can seriously threaten the conservation of biological diversity and of natural resources. Exotic European earthworms have been colonizing forest ecosystems in northeastern United States and southern Canada since the European settlement. By comparison, Asian earthworms began colonizing forests in the northeastern United States more recently. Since Asian species have biological traits compatible with a greater potential for colonization and disturbance than some European species, apprehension is growing about their dispersal into new territories. Here we review the extent of the current northern range of Asian earthworms in northeastern North America, the factors facilitating or limiting their propagation and colonization, and the potential effects of their invasion on forest ecosystems. Data compilation shows that Asian earthworms are present in all northeastern American states. So far, only one mention has been reported in Canada. Data confirm that their distribution has now reached the Canadian border, particularly along the Michigan–Ontario, New York–Ontario, Maine–New Brunswick, and Vermont–Québec frontiers. Studies report that the presence of Asian earthworms is strongly associated with human activities such as horticulture, vermicomposting, and the use of worms as fish bait. Some climatic (temperature, soil moisture) and edaphic (soil pH) factors may also influence their distribution. Controlling their dispersal at the source is essential to limiting their spread, as there is currently no effective way to eradicate established earthworm populations without unacceptable nontarget effects. Proposed management options in the United States include the prohibition of fish bait disposal and better management of the international trade of horticultural goods, commercial nurseries, and vermicomposting industries. We conclude that although regulations and awareness may delay their expansion, Asian earthworms are likely to spread further north into Canada. They are expected to cause important changes to biodiversity and dynamics of the newly invaded forest ecosystems.
by Claire Morin | 10 April 2020
Published in Front. Biogeogr. 9(4): e33282. https://doi.org/10.21425/F59433282
Climate change already affects species in many ecosystems worldwide. Since climate is an important component of a species’ ecological niche, up-to-date information about climatic niches is needed to model future species distributions in a context of climate change. The eastern red-backed salamander (Plethodon cinereus) is a wide-ranging woodland species and one of the most abundant verte-brates in northeastern North America. Though salamanders contrib-ute to several forest ecosystem functions, little is known about their climatic niche and future distribution. Using a dataset of 400,090 observations from 8302 localities in 5 Canadian provinces and 22 American states, we determined the current climatic niche of P. cinereus and predicted how the species’ distribution could shift in a context of climate change, especially in the northern part of its range. We also aimed to document factors that could affect the species’ distribution. We show that P. cinereus can live in various geographic and climatic conditions and tolerate a wide range of seasonal temperatures. The species’ current potential and future (until 2061–2080) distributions show a gap of up to 400 km with the northern limit of its current observed distribution. Assuming a mean colonization rate of approximately 100 m per year, we calculated that P. cinereus would need about 4000 years to reach the northern limit of the future distribution range modeled for the 2061–2080 period. The climate-modeled future distribution suggests that the presence of P. cinereus could decrease in the south and increase in the north. This, combined with the potential presence of habitats that are unsuitable for the species’ colonization in the north and with interspecific inter-actions in the south, could induce a contraction of the species’ range. Regardless of climate warming, the physical environment and natural and anthropic disturbances could also limit the species’ northern post-glaciation migration.
by Marie-Claude Boileau | 10 April 2020
Published in Physiologia Plantarum 165(1): 29-38. https://doi.org/doi:10.1111/ppl.12735
Black spruce (Picea mariana [Mill.] BSP) is a boreal tree species characterized by the formation of an adventitious root system. Unlike initial roots from seed germination, adventitious roots gradually appear above the root collar, until they constitute most of mature black spruce root system. Little is known about the physiological role they play and their influence on tree growth relative to initial roots. We hypothesized that adventitious roots present an advantage over initial roots in acquiring water and nutrients. To test this hypothesis, the absorptive capacities of the two root systems were explored in a controlled environment during one growing season. Black spruce seedlings were placed in a double-pot system allowing irrigation (25 and 100% water container capacity) and fertilization (with or without fertilizer) inputs independent to initial and adventitious roots. After 14 weeks, growth parameters (height, diameter, biomass), physiology (net photosynthetic rate, stomatal conductance, shoot water potential) and nutrient content (N, P, K, Ca and Mg foliar content) were compared. Most measured parameters showed no difference for the same treatment on adventitious or initial roots, except for root biomass. Indeed, fertilized black spruce seedlings invested heavily in adventitious root production, twice as much as initial roots. This was also the case when adventitious roots alone were irrigated, while seedlings with adventitious roots subjected to low irrigation produced initial root biomass equivalent to that of adventitious roots. We conclude that black spruce seedlings perform equally well through adventitious and initial roots, but if resources are abundant, they strongly promote development of adventitious roots.
by Claire Morin | 10 April 2020
Published in Forest ecology and management 442: 96-104. doi: 10.1016/j.foreco.2019.03.040
From a forest management stand point, it is crucial to know which ecological processes are most likely to drive changes in tree species distributions and abundance under warming climate conditions. In this study, we simulated forest dynamics in a 703,580 km2 territory that straddles the boreal and temperate broadleaved forest biomes in the province of Québec (Canada), under a RCP 8.5 climate change scenario. The objective was to evaluate how future forest composition is sensitive to variation in four potential drivers: fire regimes, harvesting regimes, the capacity of tree species to persist under warmer climate conditions, and species capabilities for long-distance colonization. The results indicate that forest composition in 2100 is most sensitive to variation in the parameters controlling species persistence when conditions become warmer or dryer than the conditions found in their current range. Concretely, this points to avenues of research to improve the accuracy of our predictions regarding the impacts of climate change on forest composition. For instance, we should further investigate the underlying ecological (competition) or physiological (drought stresses) processes that influence tree species persistence at the receding edge of their current distributions.
by Audrey Verreault | 10 April 2020
Published in Landscape Ecology 34: 159-174
Context: Forest landscapes at the boreal–temperate ecotone have been extensively altered. Reducing the gap between current and presettlement forest conditions through ecosystem-based forest management (EBFM) is thought to enhance ecological integrity. However, climate change may interfere with this goal and make these targets unrealistic.
Objectives: We evaluated the impacts of climate change on the ability of EBFM to reduce discrepancies between current and presettlement forest conditions in southeastern Canada.
Methods: We used early-land-survey data as well as projections from a forest landscape model (LANDISII) under four climate change scenarios and four management scenarios to evaluate future discrepancies between presettlement forest conditions and future forest landscapes.
Results: By triggering swift declines in most latesuccession boreal conifer species biomass, climate change would greatly reduce the ability of forest management to reduce the gap with presettlement forest composition, especially under severe anthropogenic climate forcing. Scenarios assuming extensive clearcutting also favor aggressive competitor species that have already increased with high historical harvest levels (e.g., poplars, maples).
Conclusions: EBFM would still be the ‘‘less bad’’ forest harvesting strategy in order to mitigate composition discrepancies with the presettlement forests, though it is likely to fail under severe climate forcing. In this latter case, one might thus question the relevancy of using presettlement forest composition as a target for restoring degraded forest landscapes. As such, we advocate that managers should relax the centrality of the reference condition and focus on functional restoration rather than aiming at reducing the gaps with presettlement forest composition per se.
