Does Ungulate Foraging Behavior in Forest Canopy Gaps Produce a Spatial Subsidy with Cascading Effects on Vegetation?

Tahtinen, Betsy; Murray, Bryan D.; Webster, Christopher R.; Tarasoff, Catherine S.; Burton, Andrew J.

doi:10.5849/forsci.13-080

Cited by 16 publications

(23 citation statements)

References 99 publications

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“…; Holmes & Webster ; Nuttle, Ristau & Royo ; Tahtinen et al . ; Dobson & Blossey ). Here, we adopt a comprehensive approach, asking how such environmental perturbations interact with direct consequences of deer herbivory to reshape woody and herbaceous communities.…”

Section: Introductionmentioning

confidence: 99%

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

et al. 2017

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Summary In forests of eastern North America, white‐tailed deer (Odocoileus virginianus) can directly affect, via herbivory, the presence, abundance and reproductive success of many plant species. In addition, deer indirectly influence understorey communities by altering environmental conditions. To examine how deer indirectly influence understorey plants via environmental modification, we sampled vegetation and environmental variables in‐ and outside deer exclosures (10–20 years old) located in temperate forests in northern Wisconsin and the Upper Peninsula of Michigan, USA. We assessed how excluding deer affected understorey community composition and structure, the soil and light environment, and relationships between direct and indirect effects, using non‐metric multidimensional scaling (NMDS), mixed linear models and nonparametric multiplicative regression (NPMR). Excluding deer altered sapling communities and several aspects of the understorey environment. Excluding deer from plots with lower overstory basal area increased sapling abundance, decreasing the amount of light available to groundlayer plants. Exclusion also reduced soil compaction and the thickness of the soil E horizon. The composition of understorey communities covaried in apparent response to the environmental factors affected by exclusion. In several common species and groups, E horizon thickness, compaction, openness, and/or total (sapling and overstory) basal area were significant predictors of plant frequency. Complementary analyses revealed that deer exclusion also altered the frequency distributions of several species and groups across environmental space. Synthesis. Deer alter many facets of the understorey environment, such as light availability, soil compaction and thickness of the soil E horizon, which, in turn, appear to mediate variation in plant communities. Those environmental modifications likely compound direct impacts of herbivory as drivers of understorey community change. Our results provide evidence that deer effects on the environment have important implications for forest composition. Thus, we suggest a re‐examination of the common assumption that understorey community shifts stem primarily from tissue removal.

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Section: Introductionmentioning

confidence: 99%

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

et al. 2017

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“…, Tahtinen et al. ) in managed forest landscapes. Second, it demonstrates how deer impacts on one vegetation strata, the sapling layer, can have indirect effects on other strata, such as the herb layer.…”

Section: Discussionmentioning

confidence: 99%

“…, Tahtinen et al. ), the influence of resource availability on plant tolerance to herbivory (Maschinski and Whitham , Strauss and Agrawal ), and plant avoidance of herbivory due to chance. These mechanisms are based on the fact that forest openings create a resource pulse of light, water, and nutrient availability (Kimmins ), producing a pulse of vegetation growth that lies within reach of ungulates.…”

Section: Discussionmentioning

confidence: 99%

“…For example, deer use of canopy gaps (up to 450 m 2 ) in a Michigan eastern hemlock ( Tsuga canadensis ) forest was greatest in gaps < 100 m 2 in area (Tahtinen et al. ). In our study, deer browsing reduced the rate of forest regeneration in patch cuts (~1.4 ha) associated with uneven‐aged silviculture, but had little effect on the rate of regeneration in clearcuts (~4.1 ha) associated with even‐aged silviculture.…”

Section: Discussionmentioning

confidence: 99%

“…() and Tahtinen et al. () have proposed that the “forage maturation hypothesis” (Fryxell ), which predicts that ungulate habitat‐use patterns vary with the stage of maturing vegetation in time and space, suggests that ungulate use of smaller forest openings is elevated for a longer period of time compared to larger openings. This occurs because edge trees shade a larger portion of smaller openings, slowing the growth rate of saplings.…”

Section: Introductionmentioning

confidence: 99%

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Ungulate impacts on herbaceous‐layer plant communities in even‐aged and uneven‐aged managed forests

et al. 2016

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Abstract. Forest management and ungulate herbivory are extant drivers of herbaceous-layer community composition and diversity. We conducted a white-tailed deer (Odocoileus virginianus) exclosure experiment across a managed landscape to determine how deer impacts interact with the type of forest management system in influencing herb-layer (all vascular plants < 0.5 m tall) species richness and composition. Our study took place 3 yr after harvest in a deciduous forest landscape being managed through even-aged (~4.1 ha openings) and uneven-aged (~1.4 ha openings) silvicultural systems. We expected the severity of deer impacts on herb layer species richness and composition to vary according to opening position, opening size, and the spatial scale of inference. At forest stand and landscape scales, species richness within silvicultural openings was greater outside compared to inside deer exclosures, and did not differ according to deer access in edges or the forest matrix. However, greater levels of species richness associated with deer access were driven by infrequently occurring forbs, and overall species composition did not differ. Notably, these species were not exotics or ferns. Deer reduced the density of large saplings and blackberry (Rubus spp.) shrubs in the smaller openings characteristic of uneven-aged management stands, but had no effect on sapling density in the larger openings characteristic of even-aged management stands. This result extends the forage maturation hypothesis to silvicultural systems, and is consistent with predictions that plant tolerance and avoidance of herbivory increase with resource availability. Deer may have facilitated the establishment of forbs in recently created silvicultural openings by temporarily slowing sapling regeneration, creating establishment sites through physical disturbance, and seed dispersal via epizoochory and endozoochory. This outcome is contingent upon declining deer visitation rates as woody vegetation matures as well as distance from source populations of exotic species. We conclude that ecological context, such as local ungulate abundance, disturbance, and landscape factors, influence how ungulates interact with forest management systems.

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A Migratory Ungulate Facilitates Cross-Boundary Nitrogen Transport in Forested Landscapes

2014

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Does Ungulate Foraging Behavior in Forest Canopy Gaps Produce a Spatial Subsidy with Cascading Effects on Vegetation?

Cited by 16 publications

References 99 publications

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

Ungulate impacts on herbaceous‐layer plant communities in even‐aged and uneven‐aged managed forests

A Migratory Ungulate Facilitates Cross-Boundary Nitrogen Transport in Forested Landscapes

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