Negligible structural development and edge influence on the understorey at 16–17-yr-old clear-cut edges in black spruce forest

Questions: What is the distance of edge influence on the structure and understorey composition at 16–17-yr-old cut edges in black spruce boreal forest? How do these edges compare with more recent 2–5-yr-old cut edges in the same region?\ud \ud Location: Northwestern Quebec, Canada.\ud \ud Methods: Forest structure and understorey composition were sampled along\ud transects perpendicular to ten 16–17-yr-old clear-cut edges, and compared to published results from 2–5-yr-old cut edges. We used randomization tests to assess themagnitude and distance of edge influence, and to compare edge influence between different edge ages.\ud \ud Results: Black spruce forest next to the 16–17-yr-old cut edges was structurally and compositionally very similar to interior forest, with little edge influence from harvesting beyond 5 m into the forest. Edge influence on the understorey was weak (low magnitude) and not very extensive (short distance) at these edges, with no significant edge influence on the abundance of individual species. Logs peaked in abundance on the forest side of the edge, with values higher than in either adjacent ecosystem.\ud \ud Conclusions: Overall, 16–17-yr-old cut edges in black spruce forest showed little evidence of further structural change compared to the 2–5-yr-old cut edges. Structural development of these edges as well as regeneration of the disturbed areas also resulted in reduced edge influence on the understorey. Instead, clearcut edges in black spruce forest may experience more forest influence on the regenerating disturbed area

Understanding patterns of biodiversity and ecosystem functioning of forested wetlands in Atlantic Canada: implications for conservation

Published versionHerein we present a selection of papers highlighting the importance of forested wetlands in Atlantic Canada. This special issue is a product of a research program on forested wetlands conducted from 2016 to 2019 and funded in part by the Atlantic Ecosystems Initiative of Environment and Climate Change Canada, Government of Canada. Although forested wetlands in Atlantic Canada have been relatively understudied, the little research available suggests these are bio-diverse ecosystems supporting rare species

Spatial patterns of structural diversity across the boreal forest-tundra ecotone in Churchill, Canada

Published versionVegetation structural diversity, also called structural complexity, has great effects on biodiversity and ecological processes, with higher biodiversity often observed in areas with higher structural diversity. As for other ecological variables, structural diversity is spatially heterogeneous. Thus, quantifying its spatial heterogeneity may provide clues to the spatial variation in ecological processes. We studied the spatial patterns of structural diversity in two different environments, tundra and forest-tundra ecotone, near Churchill, MB, Canada. We sampled vegetation and quantified five types of structural diversity (ground cover, herbaceous plants, woody plants, all live plants, and deadwood) along five transects, with lengths of 81-227 m, and used wavelet analysis to assess the scales of spatial pattern. We also assessed the effects of soil pH, microtopography, elevation, and distance from lakes on structural diversity. In general, structural diversity was spatially structured on a variety of scales, from 2 to 55 m, with larger scales being observed in the tundra than in the ecotone transects. In addition, structural diversity in the tundra was generally higher near lakes and in areas with a higher pH, whereas in the ecotone it increased mostly with increasing pH and microtopographic variation. Spatial heterogeneity is an important characteristic of the forest-tundra ecotone and even tundra areas that appear homogeneous are structurally diverse at a variety of scales

THE IMPACT OF MOOSE (Alces alces andersoni) ON FOREST REGENERATION FOLLOWING A SEVERE SPRUCE BUDWORM OUTBREAK IN THE CAPE BRETON HIGHLANDS, NOVA SCOTIA, CANADA

Two interacting disturbances such as stand-level defoliation by spruce budworm (Choristoneura fumiferana) and subsequent herbivory by moose (Alces alces) may affect landscapes differently than if they occurred in isolation. We studied moose (A. a. andersoni) browsing on sites disturbed approximately 25 years ago by a severe spruce budworm outbreak in a region historically dominated by balsam fir (Abies balsamea) forest on northern Cape Breton Island, Nova Scotia, Canada. Our objectives were to 1) describe the impact of a large resident moose population on post-budworm regeneration of balsam fir and white birch (Betula papyrifera), and 2) to examine the interplay between moose abundance, site conditions, and variation in post-budworm forest regeneration. Fifty-eight ran­domly located sites were sampled for composition and structural characteristics, moose browse severity, moose pellet group density, and site conditions. We used univariate general linear modelling (GLM) and multivariate redundancy analysis (RDA) to examine relationships between moose abundance as indicated by pellet-groups, site conditions, and post-budworm regeneration. Approximately 65% of all balsam fir and white birch saplings tallied were severely browsed by moose, exhibiting stunted, abnormal growth forms. Both the GLM and the RDA indicated that moose abundance was the best predictor of variation in the density of post-budworm regeneration of balsam fir and white birch. Site conditions were less useful predictors of variation in regeneration. The relationship between moose abundance and regeneration of balsam fir and white birch was positive, suggesting that moose may be more abundant in areas where regeneration is denser. Sustained, severe browsing in areas regenerating after spruce budworm outbreak may significantly inhibit future forest development and alter the well documented spruce budworm-balsam fir cyclic successional system of northern Cape Breton Island

Moose impacts on forest regeneration

Published versionTwo interacting disturbances such as stand-level defoliation by spruce budworm (Choristoneura fumiferana) and subsequent herbivory by moose (Alces alces) may affect landscapes differently than if they occurred in isolation. We studied moose (A. a. andersoni) browsing on sites disturbed approximately 25 years ago by a severe spruce budworm outbreak in a region historically dominated by balsam fir (Abies balsamea) forest on northern Cape Breton Island, Nova Scotia, Canada. Our objectives were to 1) describe the impact of a large resident moose population on post-budworm regeneration of balsam fir and white birch (Betula papyrifera), and 2) to examine the interplay between moose abundance, site conditions, and variation in post-budworm forest regeneration. Fifty-eight ran­domly located sites were sampled for composition and structural characteristics, moose browse severity, moose pellet group density, and site conditions. We used univariate general linear modelling (GLM) and multivariate redundancy analysis (RDA) to examine relationships between moose abundance as indicated by pellet-groups, site conditions, and post-budworm regeneration. Approximately 65% of all balsam fir and white birch saplings tallied were severely browsed by moose, exhibiting stunted, abnormal growth forms. Both the GLM and the RDA indicated that moose abundance was the best predictor of variation in the density of post-budworm regeneration of balsam fir and white birch. Site conditions were less useful predictors of variation in regeneration. The relationship between moose abundance and regeneration of balsam fir and white birch was positive, suggesting that moose may be more abundant in areas where regeneration is denser. Sustained, severe browsing in areas regenerating after spruce budworm outbreak may significantly inhibit future forest development and alter the well documented spruce budworm-balsam fir cyclic successional system of northern Cape Breton Island

Quantifying distance of edge influence: a comparison of methods and a new randomization method

Published VersionDespite many studies on edge influence in forests, there is no common method for estimating distance of edge influence (DEI, = edge width). We introduce a new randomization method (RTEI) for estimating DEI that tests the significance of edge influence compared to the reference forest. Using artificial datasets we compared DEI as estimated by nine different methods and examined effects of sampling design and the nature of the edge response. DEI estimates varied widely among methods; parametric, randomization and curve-fitting analyses produced the lowest, intermediate and greatest values, respectively. Sampling design and the nature of the edge response affected estimates of DEI differently among methods. RTEI was the only method that was generally invariable to sampling design while being sensitive to variation in the reference ecosystem but not at the edge. A standard method of quantifying DEI is important for comparing edge responses among different studies for conservation research

Patterns of shrub abundance and relationships with other plant types within the forest–tundra ecotone in northern Canada

Published VersionThroughout the forest–tundra ecotone where trees and tall shrubs are becoming more abundant, knowledge of associations between shrubs and surrounding vegetation could inform predictions of their changing relationships. We assessed shrubs in 1 m × 1 m contiguous quadrats along two ∼450 m transects across tundra and ecotone landscapes near Churchill, Canada to determine patterns in relation to lakeshore edges, soil pH, microtopography, and other plant groups. We used wavelet analysis to assess patterns and generalized least squares for relationships with environmental variables. Shrubs were taller and more diverse at edges, particularly in tundra. The ecotone was more complex than tundra with greater variation in tall shrub and tree cover, shrub height, and microtopography. Shrub richness was positively correlated with microtopography but exhibited no relationship with pH. Bivariate relationships of shrubs with other plant groups varied for different scales. In tundra, shrub richness was negatively correlated with graminoids, forbs, and moss, but positively correlated with lichens within 1 m; opposite relationships were found at 4–60 m scales. Relationships in the ecotone were reversed and more complex at different scales. As trees encroach in the tundra, the spatial pattern of shrubs will become more complex at a variety of scales, likely with cascading effects on other plant types

Spatial patterns of vegetation structure and structural diversity across edges between forested wetlands and upland forest in Atlantic Canada

Accepted versionForested wetlands are an integral but understudied part of heterogeneous landscapes in Atlantic Canada, although they are known to provide habitat for species at risk. Our objectives were to explore patterns of forest structure across edges between forested wetland and upland forest, to locate changes in vegetation structure and to assess multivariate relationships in vegetation structure. Our study sites were in temperate (Acadian) forested wetland landscapes. We sampled trees and recorded canopy cover every 20 m along 120-m-long transects. We estimated the cover of trees, saplings, shrubs in three height classes, Sphagnum, other bryophytes, lichens, graminoids, ferns, and forbs in contiguous 1 m × 1 m quadrats. We calculated structural diversity using the Shannon index and used wavelet analysis to assess spatial patterns. We found few clear patterns except for lower tree structural diversity at the edge of forested wetlands. Structural diversity was not a reliable measure for distinguishing forested wetland from upland forest. Forested wetlands are an integral part of many forested landscapes in Atlantic Canada, but their detection and differentiation from surrounding ecosystems can be difficult. Policy should err on the side of caution when mapping forested wetlands and include them in wetland protection

Assisted Revegetation in a Subarctic Environment: Effects of Fertilization on the Performance of Three Indigenous Plant Species

Published VersionAssisted re-vegetation is particularly difficult in subarctic and arctic ecosystems where the impact of anthropogenic activities can be extensive and natural plant regeneration is slow. The construction of a military base in the 1950s at Kuujjuarapik–Whapmagoostui in northern Quebec destroyed most of the vegetation cover. Afterwards, other anthropogenic disturbances linked to the village expansion (housing, ATV traffic, pedestrian trampling) have slowed down the recovery process. To provide residents with low-cost but efficient assisted revegetation techniques, we evaluated the performance (seedling emergence, survival, and biomass production) of three indigenous plant species (Leymus mollis, Lathyrus japonicus, Trisetum spicatum) submitted to different levels of mineral and organic fertilizer additions in both a greenhouse experiment and a field plantation in the village. In the greenhouse experiment, moderate mineral fertilization had positive impacts on seedling emergence and both above ground and below ground biomass of L. mollis. The magnitude of this impact on biomass was greater when mineral fertilization was combined with organic fertilization. The effects of mineral fertilization were negative on the other two species, especially at higher fertilization levels. However, after two growing seasons, a moderate level of mineral fertilizer in the field plantation had positive effects on the cover and above ground biomass of all three species. Overall, organic fertilization from the substrate of a nearby marsh did not enhance plant performance in either experiment. Planting seeds of L. mollis or T. spicatum in combination with a moderate level of mineral fertilization at the time of planting provides a low-cost assisted re-vegetation treatment for subarctic villages

The role of the circumarctic forest–tundra ecotone for Arctic biodiversity

Accepted VersionThe arctic forest–tundra ecotone (FTE), which links species communities of the boreal forest with those of the arctic tundra, is expected to respond swiftly to climate change with a profound reduction of tundra as the dominating scenario. With its circumarctic expanse and up to several hundred kilometres in width, the zone occupies a large part of the vegetated surface at high latitudes. Relocation and structural changes of the ecotone vegetation will affect not only plant but also animal and other biological diversity. A large number of arctic species are dependent on the forest–tundra ecotone in terms of food and habitat during parts of their life cycle or annual migration. In the ‘Arctic Species Trend Index’, developed to provide trends in arctic vertebrates, more than half of the species and data are from the forest–tundra ecotone. However, in assessments of arctic biodiversity, only the northernmost tundra-dominated areas of the ecotone are included. This is unfortunate and somewhat problematic since the treed part that serves as a source of seeds for new seedlings and saplings in the tundra-dominated part is excluded. This inconsistency hampers monitoring efficiency and biodiversity conservation efforts. During the International Polar Year, a large international research project on the forest–tundra ecotone established numerous sites around the circumpolar north where causes and consequences of vegetation change were analyzed. This network of sites and data forms an excellent basis for necessary monitoring of the spatial and temporal complexity of forest encroachment into tundra and its relation to arctic biodiversity