The impact of deer on relationships between tree growth and mortality in an old-growth beech-maple forest

Aggregations of dead wood after wildfire act as browsing refugia for seedlings of Populus tremula and Salix caprea

We evaluated the impact of chronic deer over browsing on the diversity and abundance of understory forbs and shrubs within a forest stand in the Allegheny High Plateau Region of Pennsylvania by comparing vegetation inside a 60-year-old exclosure to vegetation within an adjacent reference site. This is the oldest known exclosure in the Eastern Deciduous Forest. Browsing caused the formation of an extremely low diversity herbaceous understory dominated by a single fern species, caused the local extirpation of shrubs, and drove forbs to extremely low abundance (< 0.2% cover m−2 vs. 43% inside the exclosure). Our results confirm previous findings that demonstrate that browsing has caused 60–80% declines in herb and shrub richness regionally. Because many of these species have low dispersal and reproductive rates, we predict long-term legacy effects if deer numbers are ever reduced. Our results combined with other studies provide information on shrub and herb abundance in the absence of browsing that ...

https://www.nrs.fs.fed.us/pubs/jrnl/2011/nrs_2011_goetsch_001.pdf

Chronic over browsing and biodiversity collapse in a forest understory in Pennsylvania: Results from a 60 year-old deer exclusion plot

We studied the effects of browsing by Odocoileus virginianus (white-tailed deer) on the native and non-native vegetation in a mixed oak-beech forest in Rock Creek Park, Washington, DC. We compared the thickness and cover of vegetation up to 2 m in height, and species richness of native and non-native plants in 17 exclosed (1 × 4 m) and 17 control plots from 2001–2004. Over the four-year period, foraging by deer suppressed the thickness of vegetation ≤ 1 m in height, reduced the cover of herbaceous, woody, and native plants, and generally decreased the species richness of native and woody plants. Browsing had no effects on the species richness of non-native plants, but generally reduced the prevalence of Celastrus orbiculatus (oriental bittersweet). Of the dominant canopy species, browsing affected Quercus spp. (oak) regeneration, but had no apparent effects on Fagus grandifolia (American beech). These results indicate that white-tailed deer are having a detrimental effect on the structure and spe...

Effects of Deer Browsing on Native and Non-native Vegetation in a Mixed Oak-Beech Forest on the Atlantic Coastal Plain

We evaluated the impact of long-term over-browsing by white-tailed deer on the diversity and density of trees in a forest in the Allegheny High Plateau region of central Pennsylvania. We compared tree diversity and density inside a 60 year-old deer exclosure to an adjacent reference site. Browsing caused a 55–100% decline in density of four tree species (Prunus serotina, Acer saccharum, Betula lenta, Cornus alternifolia) and created a forest dominated (> 70% of all stems) by Acer pensylvanicum, an understory tree that is known to be highly browse-tolerant. The total density of trees that are capable of ascending into the canopy (i.e., non subcanopy tree species) declined by 85%. Browsing caused a significant decline in both mean species richness and Shannon diversity and created communities that contrasted significantly in tree species composition (ANOSIM, R  =  0.8105, P < 0.0001). Our results suggest that long-term over-browsing can create low density, depauperate communities where dominance is...

https://www.nrs.fs.fed.us/pubs/jrnl/2011/nrs_2011_kain_001.pdf

Over-browsing in Pennsylvania creates a depauperate forest dominated by an understory tree: Results from a 60-year-old deer exclosure

We surveyed the vegetation growing on the surface of tall boulders (>1.5 m), on the surface of short boulders (<0.5 m) and in areas adjacent to these boulders on the soil surface in the Allegheny National Forest, Pennsylvania. Our purpose was to test the hypothesis that tall boulders serve as refugia from deer browsing for both woody plant species as well as understory herbs. We conducted our surveys during spring when many of these herbs reproduce sexually and their inflorescences are vulnerable to browsing. Deer cannot gain access and browse on these tall boulders, whereas they can easily browse plant species on shorter boulders and on the forest floor. We predicted that the tall boulders would have the highest plant diversity, woody species density and the density of reproductive individuals of understory herbs. We found a total of more than 1300 reproductive individuals of flowering herbs of more than 10 species growing on tall boulders and only 6 reproductive individuals of only a few species growing on the soil surface. Overall, there was a much greater density and diversity of woody species and sexually reproducing herbs on tall boulders or Rock Refugia Gardens than either on short boulders or the soil surface. Because the diversity and abundance of vegetation on the short boulders was nearly identical to that on the forest floor, our findings are unlikely to be explained by tall boulders providing a superior edaphic or abiotic habitat relative to habitats on the forest floor. Species accumulation curves showed that plant species continued to accrue with area on tall boulders, but did not increase with area on the forest floor or on the short boulders. These Rock Refugia Gardens demonstrate the pervasive and deleterious impact that deer are having on plant species diversity and forest regeneration in the Allegheny National Forest and likely elsewhere in the eastern US where these vertebrates are abundant.

https://www.nrs.fs.fed.us/pubs/jrnl/2005/nrs_2005_comisky_001.pdf

Lauren Comisky

Papers

Deer Browsing Creates Rock Refugia Gardens on Large Boulders in the Allegheny National Forest, Pennsylvania