Sammendrag
Forest management can enhance the ecosystem services forests provide, but it can also alter the capacity of
forests to provide those services in the future. Ecosystem-based management has been widely implemented to
mitigate the deterioration of forest ecosystems by reducing dissimilarities between managed and natural forests.
Ecosystem-based management objectives generally aim to maintain community composition, stand structure,
ecosystem functions and services. Heavy browsing pressure by ungulates at densities unrepresentative of past
abundance could interfere with these objectives by chronically and selectively browsing tree regeneration
following logging.
Using a browsing exclusion experiment, we investigated how the effects of different moose browsing pressures
on tree regeneration could interfere with ecosystem management objectives in boreal forests of Quebec, Canada.
Management objectives in this region include, among others, reaching targeted coniferous trees densities for
commercial harvest, favouring the conservation of birches (Betula spp.) to maintain soil quality and conserving
fruit-bearing trees due to their ecological significance for biodiversity. We used path analyses to differentiate
direct and indirect effects of moose on seedling density and mixed models to investigate how browsing affected
sapling recruitment and whether resulting densities are compatible with ecosystem management objectives.
By directly reducing the overall sapling density, moose browsing indirectly increased seedlings densities of all
deciduous species. This indirect effect increased with browsing pressure and favoured raspberry cover, which
was positively or negatively linked to seedling density, depending on tree species. Moderate and heavier
browsing pressures reduced coniferous sapling density below the ecosystem management target. Moose suppressed
birch saplings so that the minimal target of 50 birches ha− 1 was not met under heavier browsing
pressure. Sapling density of fruit-bearing trees was low under all browsing pressures when compared to
exclosures.
Policy implications
Heavy moose browsing is preventing the achievement of ecosystem management objectives in our study area.
Positive indirect effects on seedling densities suggest that reducing moose density could allow released seedlings
to replenish the sapling layer, but we discuss why this would not guarantee reaching ecosystem management
objectives. To help forest managers evaluate and respond to challenges posed by high ungulate densities, we
suggest incorporating browsing inventories in national forest surveys to monitor this chronic disturbance and
modulate decisions for forest ecosystem management.
Ungulate
Moose
Alces alces
Forest regeneration
Browsing
Forest ecology
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