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Through their foraging and habitat selection, white-tailed deer (Odocoileus virginianus) can have profound effects on forest plant communities that produce persistent legacy effects. To examine the duration of persistence of potential legacy effects, we investigated the long-term consequences of deer herbivory in plant communities following canopy gap creation in a hemlock–northern hardwood forest in the Upper Peninsula of Michigan. Twenty artificial canopy gaps were created during the winter of 2002–03: seven small gaps (50–150 m2), seven medium gaps (151–250 m2), and six large gaps (251–450 m2). Herbaceous layer communities were sampled within arrays of exclosed and nonexclosed sample plots, established within a few years of gap creation, during the summer of 2020 and compared to a previous study conducted in 2007. Eighteen years following canopy gap creation, herbaceous layer communities exhibited both persistent and transient legacies of deer herbivory. Persistent legacies included similarity of small to large gaps compositionally and low abundance of browse-sensitive species outside of exclosures. Transient patterns included initial high graminoid cover and low cover of trees in the ground layer outside of exclosures and differences in diversity between gap size classes. Some emergent patterns were also observed, including declining floristic quality indices over time but sustained high occurrence of a number of species with moderately high coefficients of conservatism on deer access plots, albeit at low abundance. Differential compositional trajectories emerged based on gap-specific tree species colonization patterns. Our results suggest that through differential foraging patch selection and control of woody regeneration, white-tailed deer may alter or reinforce patterns of dominance depending on initial conditions. These interactions may result in context-specific persistent, transient, and emergent dynamics as plant communities recover from canopy disturbance. [ABSTRACT FROM AUTHOR]

Plant–herbivore interactions account for much of the biodiversity observed in an ecosystem. Plants may alter defense expression dependent on the specific herbivore present. Many studies focus on the optimization of these defenses against a single herbivore, but in an ecological context, there may be a myriad of herbivores at any given time. We designed a study to examine defenses employed by swamp white oak (Quercus bicolor) against insects and large mammals. We established six deer exclosures with trees located inside and outside each exclosure. Outside the exclosures, physical constraints only allow deer to feed up to a browseline on trees, whereas insects can potentially access all portions of the tree. Trees inside exclosures were only accessible to insect herbivores. Furthermore, insecticides were applied to half of the exclosures to create insect‐free (i.e., insecticide applied), deer‐free (i.e., inside exclosures), deer‐only (i.e., outside exclosures with insecticide), and herbivore‐free (i.e., inside exclosures with insecticide) environments. This design allowed us to analyze simultaneous defensive responses of individual trees to mammal and insect herbivores. We predicted that because insects represent a continuous threat, plants should invest in fixed concentrations of defenses (e.g., polyphenols, tannins, and condensed tannins), even when deer are absent. When deer are present, plants should increase investment in defenses in tissues that deer have access to. We found that plant defense strategies varied spatially on individual trees. When only insects were present, nutritional constituents (e.g., nitrogen and non‐structural carbohydrates) did not change but antinutritional constituents increased. Contrastingly, when deer were present, both nutritional and antinutritional constituents decreased. We found a decrease in insect functional group diversity when deer were present. Our findings suggest that plants may partition defense strategies depending on the most prominent herbivore pressure. However, changes in insect functional group diversity may result from either changes in plant defense strategy or intraspecific competition among multiple herbivores. Future studies should investigate patterns of chemical heterogeneity displayed by plants in response to diverse herbivore pressures. [ABSTRACT FROM AUTHOR]

Abstract Plant–herbivore interactions account for much of the biodiversity observed in an ecosystem. Plants may alter defense expression dependent on the specific herbivore present. Many studies focus on the optimization of these defenses against a single herbivore, but in an ecological context, there may be a myriad of herbivores at any given time. We designed a study to examine defenses employed by swamp white oak (Quercus bicolor) against insects and large mammals. We established six deer exclosures with trees located inside and outside each exclosure. Outside the exclosures, physical constraints only allow deer to feed up to a browseline on trees, whereas insects can potentially access all portions of the tree. Trees inside exclosures were only accessible to insect herbivores. Furthermore, insecticides were applied to half of the exclosures to create insect‐free (i.e., insecticide applied), deer‐free (i.e., inside exclosures), deer‐only (i.e., outside exclosures with insecticide), and herbivore‐free (i.e., inside exclosures with insecticide) environments. This design allowed us to analyze simultaneous defensive responses of individual trees to mammal and insect herbivores. We predicted that because insects represent a continuous threat, plants should invest in fixed concentrations of defenses (e.g., polyphenols, tannins, and condensed tannins), even when deer are absent. When deer are present, plants should increase investment in defenses in tissues that deer have access to. We found that plant defense strategies varied spatially on individual trees. When only insects were present, nutritional constituents (e.g., nitrogen and non‐structural carbohydrates) did not change but antinutritional constituents increased. Contrastingly, when deer were present, both nutritional and antinutritional constituents decreased. We found a decrease in insect functional group diversity when deer were present. Our findings suggest that plants may partition defense strategies depending on the most prominent herbivore pressure. However, changes in insect functional group diversity may result from either changes in plant defense strategy or intraspecific competition among multiple herbivores. Future studies should investigate patterns of chemical heterogeneity displayed by plants in response to diverse herbivore pressures.

We propose that small patches of land protected by low (1.2-m tall) fence is a viable approach for restoring and/or conserving forests in riparian or upland areas with high white-tailed deer (Odocoileus virginianus Zimmerman) populations. We also propose that this new approach may be advantageous because, unlike tree shelters, fenced areas protect shrubs just as well as trees in afforestation projects. Multi-year field experiments were performed involving deer exclosures where fence height and fenced area were manipulated in upland and lowland pasture and forest settings. Results show that low fencing significantly increased seedling survival and growth relative to unfenced areas when fenced areas were small (i.e., less than or equal to ∼100 m2). Moreover, tall fencing (1.8 or 2.3 m) did not provide significantly greater protection than shorter (1.2-m) fencing when the fenced areas were kept small. We propose that creating small patches of deer-free pasture or forest habitat will greatly support new approaches to afforestation such as applied nucleation. Finally, we show that low-stature fencing may also have application for protecting larger areas (≥0.8 ha) if the fencing is deployed around the perimeter as two low fences erected in parallel and with a small (3-m) space between them. We conclude that low fencing can result in levels of survival and growth of both trees and shrubs suitable to meet the success criteria for afforestation projects funded by the US federal government. [ABSTRACT FROM AUTHOR]

Deer support high tick intensities, perpetuating tick populations, but they do not support tick-borne pathogen transmission, so are dilution hosts. We test the hypothesis that absence of deer (loss of a dilution host) will result in either an increase or a reduction in tick density, and that the outcome is scale dependent. We use a complementary methodological approach starting with meta-analysis, followed up by a field experiment. Meta-analysis indicated that larger deer exclosures reduce questing (host-seeking) tick density, but as the exclosure becomes smaller (<2.5 ha) the questing tick density is increased (amplified). To determine the consequences for tick-borne pathogen transmission we carried out a field experiment, comparing the intensity of ticks that fed on hosts competent for tick-borne pathogen transmission (rodents) in two small (<1 ha) deer exclosures and their replicated controls. Intensity of larval ticks on rodents was not significantly different between treatments, but nymph intensity, the tick stage responsible for tick-borne encephalitis (TBE) transmission, was higher in deer exclosures. TBE seropositive rodents were found in a deer exclosure but not in the controls. We propose that localized absence of deer (loss of a dilution host) increases tick feeding on rodents, leading to the potential for tick-borne disease hotspots. [ABSTRACT FROM AUTHOR]

Abstract: Chronic herbivory by white-tailed deer (Odocoileus virginianus Zimmerman) can have profound impacts on the function and structure of forest ecosystems. We examined the combined influence of intense herbivory associated with a deer population eruption and chronic herbivory by the post eruption population on the spring flora of Cades Cove, Great Smoky Mountains National Park. During the 1970s the deer population reached a peak of 43 deer per km2, from which it has slowly declined in recent decades. To examine the influence of intense herbivory, we compared the abundance and flowering rates of early flowering plants in Cades Cove to a nearby reference site with similar bedrock geology, vegetation, and disturbance history but contrasting history of deer abundance. Our results suggest that significant changes (p ⩽0.05) in the diversity, evenness, and species richness of the spring flora occurred during the eruptive phase. Trillium spp. and other liliaceous species appeared to be disproportionately impacted. Comparisons between control and exclosure plots established after the deer population eruption indicate that recovery has been largely restricted to species that were able to persist under intense herbivory. These species have increased in number in exclosures, suggesting continued impacts by deer on the plant community outside the exclosures. Little to no recolonization by browse sensitive species was observed. Consequently, to restore the natural diversity of early flowering plants once present in Cades Cove, active restoration may be necessary in addition to maintaining deer densities below current levels. [Copyright &y& Elsevier]