Wolf, elk, and aspen food web relationships: Context and complexity
- Department of Forest Ecosystems and Society, College of Forestry,
- Oregon State University, Corvallis, OR, USA
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Abstract
Like most ecological communities, aspen
(Populus tremuloides) forests are influenced
by a synergy of bottom-up (resources-driven)
and top-down (predator-driven) processes.
Since the 1920s, ecologists have observed
the decline of many aspen communities
throughout the Intermountain West. The extent
and possible drivers of this decline are topics of
much recent scientific study.
(Populus tremuloides) forests are influenced
by a synergy of bottom-up (resources-driven)
and top-down (predator-driven) processes.
Since the 1920s, ecologists have observed
the decline of many aspen communities
throughout the Intermountain West. The extent
and possible drivers of this decline are topics of
much recent scientific study.
In addition to bottom-up effects, which include
drought, fire suppression, and disease, ungulate
herbivory is a contributing factor. Trophic
cascades are ecological relationships in which
an apex predator produces strong top-down,
direct effects on its prey and indirect changes
in faunal and floral communities at lower
trophic levels. Apex predators, such as the
gray wolf (Canis lupus), have been linked to
aspen vigor and recruitment, via trophic
cascades mechanisms.
drought, fire suppression, and disease, ungulate
herbivory is a contributing factor. Trophic
cascades are ecological relationships in which
an apex predator produces strong top-down,
direct effects on its prey and indirect changes
in faunal and floral communities at lower
trophic levels. Apex predators, such as the
gray wolf (Canis lupus), have been linked to
aspen vigor and recruitment, via trophic
cascades mechanisms.
Scientists
have
hypothesized
that returning wolves to the landscape enables
aspen to recruit into the forest overstory, via
the density-mediated and behaviorally-mediated
effects of wolves on their ungulate prey,
primarily elk (Cervus elaphus). We present
a synthesis of scientific findings on this topic,
identify trends in the ecological impacts of
wolves in aspen communities in a variety of
ecosystems, and suggest areas for further
investigation.
Knowledge gaps include the interaction of
top-down (e.g., predators) and bottom-up
(e.g., drought, fire, hydrology, logging)
effects, and how the ecological context of
the interaction affects the outcome. Future
horizons involve exploring these food web
relationships as a complex of inter-level
interactions in a more integrated, empirical
manner. We suggest adopting a new standard
for the aspen/wolf ecology literature by shifting
its emphasis and lexicon from trophic cascades
to food web studies. Such an integrated
approach can help managers create more
resilient aspen communities.
top-down (e.g., predators) and bottom-up
(e.g., drought, fire, hydrology, logging)
effects, and how the ecological context of
the interaction affects the outcome. Future
horizons involve exploring these food web
relationships as a complex of inter-level
interactions in a more integrated, empirical
manner. We suggest adopting a new standard
for the aspen/wolf ecology literature by shifting
its emphasis and lexicon from trophic cascades
to food web studies. Such an integrated
approach can help managers create more
resilient aspen communities.
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