Degradation of Boreal Forests by Nonnative Herbivores in Newfoundland's National Parks: Recommendations for Ecosystem Restoration

Gosse, John W.; Hermanutz, Luise; McLaren, Brian; Deering, P.; Knight, Tom

doi:10.3375/043.031.0403

Cited by 44 publications

(70 citation statements)

References 60 publications

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“…This, in turn, has significantly modified plant community composition and structure (e.g., Estes et al 2011). In boreal and temperate forests, high densities of white-tailed deer (Odocoileus virginianus) and moose (Alces alces) have led to dominance of grasses, sedges, and ferns at the expense of browse-sensitive herbs and woody shrubs (Tremblay et al 2006, Rooney 2009, Gosse et al 2011. Such a field layer can be hard for woody species to penetrate and has therefore been termed a recalcitrant understory (Royo and Carson 2006).…”

Section: Introductionmentioning

confidence: 99%

A large herbivore triggers alternative successional trajectories in the boreal forest

Hidding

Tremblay

Côté

2013

Ecology

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Abstract. Alternative successional trajectories (AST) may result in multiple climax states within an ecosystem when disturbances affect colonization history. In the boreal forest, ungulates have been proposed to drive AST because, under herbivore pressure, preferred species may go extinct and apparent competition may benefit browsing-resistant species. Over a 15-year period following logging, we tested whether deer herbivory altered plant species composition and whether the competitive advantage of resistant species was maintained following herbivore removal. We compared exclosures built immediately after logging with delayed exclosures built eight years later on Anticosti Island, Quebec, Canada. Although the palatable tree Betula papyrifera (paper birch) and some palatable herbs recovered in delayed exclosures, we observed legacies in both tree and herb cover. Woody regeneration in delayed exclosures was dominated by Picea glauca (white spruce), and Poaceae (grasses) were abundant in the field layer. Given that only early-successional species recovered, whereas latesuccessional broadleaf species and Abies balsamea (balsam fir) remained rare, succession may follow an AST after a limited browsing period during early succession.

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Section: Introductionmentioning

confidence: 99%

A large herbivore triggers alternative successional trajectories in the boreal forest

Hidding

Tremblay

Côté

2013

Ecology

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“…Where mature forest stands are lost by natural disturbance or senescence, regenerating stands in areas with hyperabundant moose are characterized by heavily damaged balsam fir saplings that display growth stunted to < 0.6 m height by repeated browsing of the leader; this browsing eventually leads to the death of saplings and greatly reduced sapling density (Bergerud & Manuel, 1968;Gosse et al, 2011). This leads to the creation of open 'moose meadows', characterized by grasses, ferns, non-palatable woody shrubs and a low-density canopy of less-palatable spruce and mature white birch (Gosse et al, 2011). This leads to the creation of open 'moose meadows', characterized by grasses, ferns, non-palatable woody shrubs and a low-density canopy of less-palatable spruce and mature white birch (Gosse et al, 2011).…”

Section: Study Areamentioning

confidence: 99%

Multiscale impacts of forest degradation through browsing by hyperabundant moose (Alces alces) on songbird assemblages

Rae

Whitaker

Warkentin

2013

Diversity and Distributions

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Aim Songbirds are sensitive to changes in forest structure and composition at various spatial scales, particularly during the breeding season. Habitat degradation associated with herbivore browsing may contribute to declines in songbird populations. Here, we evaluate songbird responses to herbivore-induced habitat change at multiple spatial scales.Location In Gros Morne National Park (GMNP), Newfoundland, Canada, browsing by hyperabundant moose (Alces alces) has changed forest structure by reducing understorey cover and converting regenerating stands to open areas dominated by grasses and shrubs.Methods We conducted point count surveys to measure bird occurrence throughout GMNP during the 2010 breeding season. Using vegetation information from ground plots and remote sensing, we characterized habitat at three scales: local, neighbourhood and landscape. Following a two-step procedure to model species occurrence with habitat, the most important habitat factors within each scale were retained for cross-scale modelling.Results Cross-scale models revealed patterns in the association of songbird habitat assemblages with moose-altered habitats. Early successional species such as mourning warbler (Geothlypis philadelphia) were positively associated with moose-browsed habitat at the landscape scale. Forest interior specialist (e.g. black-throated green warbler, Setophaga virens) and generalist species (e.g. boreal chickadee, Poecile hudsonicus) were negatively associated with moosebrowsed habitat at the neighbourhood scale. Local songbird species richness was independent of moose-browsed habitat at any scale.Main conclusions The influence of intense browsing on forest songbirds varies by species but has the potential to extend beyond the area of immediate impact. Continued intense browsing and resulting forest alteration could cause declines in forest specialists and generalists, but may increase populations of early successional species. To maintain bird assemblages characteristic of the region, we recommend management actions that lower moose density in areas with hyperabundant populations such as GMNP to maintain forest structure and regeneration comparable to that present prior to the introduction of moose.

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“…After canopy opening, moose maintain gap susceptibility to invasion by focusing their browsing on the highly palatable species that revegetate early successional stands (Rose and Hermanutz 2004;Forbes 2006;Gosse 2006;Gosse et al 2011). This activity combined with trampling of native vegetation maintains high light availability and creates competitionfree, bare ground sites.…”

Section: Introductionmentioning

confidence: 98%

“…Forests act as a relatively continuous barrier to wind dispersal of alien plant seeds (Brothers and Spingarn 1992) and the low light availability, soil pH, and nutrient availability in undisturbed forest canopies, which often separate gap openings by great distances, are unsuitable for shade-intolerant herbs such as C. arvense (Bakker 1960;Haber 1997;Rose 2002). In GMNP, it appears that these obstacles to invasion have been overcome as a result of direct and indirect facilitation by the high density of non-native moose (Alces alces L.; Rose and Hermanutz 2004;Gosse et al 2011).…”

Section: Introductionmentioning

confidence: 98%

Impacts of non-native plant and animal invaders on gap regeneration in a protected boreal forest

Humber

Hermanutz

2011

Biol Invasions

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In balsam fir (Abies balsamea)-dominated boreal forests of Gros Morne National Park, Newfoundland (Canada), non-native Cirsium arvense (Canada thistle) has invaded forest gaps. Its management is complicated by the lack of viable control techniques and an overarching issue of gap regeneration failure attributed to browsing by non-native moose (Alces alces). This study identifies the impacts of thistle invasion on balsam fir regeneration and explores protocols to re-establish fir in gaps invaded by thistle and moose. Fir seeds were planted into ten gaps (five natural; five anthropogenic) and the emergence, growth, herbivory damage, and survival of fir was determined for 2 years amongst five treatments (n = 50 plots; 32 seeds/plot): (1) thistle monocultures in gaps; (2) where aboveground thistle biomass was removed; (3) where above-and below-ground thistle biomass was removed; (4) non-invaded areas in gaps; and, (5) adjacent uninvaded forest edges. In addition, 432 fir seedlings (aged 15 months) were transplanted into four forest gaps within the above treatments and followed for 1 year. Results indicate that invasion of C. arvense negatively affects fir emergence and early survival, and may further contribute to continued balsam fir regeneration failure independent of future moose densities. However, older fir seedlings transplanted into thistle monocultures experienced a positive facilitative effect due to the protection thistle provided against small mammal herbivory. Restoration actions that combine moose density reductions with the planting of fir seedlings offers the most viable long-term strategy to re-establish the native forest canopy in thistle-invaded gaps and would likely lead to the eventual decline of shade-intolerant C. arvense.

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Degradation of Boreal Forests by Nonnative Herbivores in Newfoundland's National Parks: Recommendations for Ecosystem Restoration

Cited by 44 publications

References 60 publications

A large herbivore triggers alternative successional trajectories in the boreal forest

A large herbivore triggers alternative successional trajectories in the boreal forest

Multiscale impacts of forest degradation through browsing by hyperabundant moose (Alces alces) on songbird assemblages

Impacts of non-native plant and animal invaders on gap regeneration in a protected boreal forest

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