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Natural Areas Journal

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Natural Areas JournalJanuary 2005Volume 25, Number 2Table of Contents continued 202 Book Reviews Protected Areas and the Regional Planning Imperative in North America, Nelson, Day, Sportza, Louckey, and Vasquez ◆ A Citizen’s Guide to Ecology, Slobodkin ◆ The Russian Far East: a Reference Guide for Conservation and Development, 2nd ed., Newell ◆ Drafting a Conservation Blueprint: a Practitioner’s Guide to Planning for Biodiversity, Groves ◆ Community Forestry in the United States: Learning from the Past, Crafting the Future, Baker and Kusel 209 Review of Current Literature CORRECTIONOn the back cover of the January 2005 issue of Natural Areas Journal (Vol. 25, no. 1), the list of authors of the last paper in the issue is incorrect. The correct listing should have been: 91 Land Trust Activity and Highest and Best Uses Under Conservation Easements in Georgia, USA Columbia L. Crehan, David H. Newman, Warren A. Flick, and Hans NeuhauserWe regret this error.CORRECTIONIn the the January 2005 issue of Natural Areas Journal (Vol. 25, no. 1), the list of authors was shown in the wrong order for the paper “Plant Communities Growing on Boulders in the Allegheny National Forest: Evidence for Boulders as Refugia From Deer and as a Bioassay of Overbrowsing,” pp. 10-18. The correct order of the authors is: Joshua A. Banta, Alejandro A. Royo, Chad Kirschbaum, and Walter P. CarsonWe regret this error.10 Natural Areas Journal Volume 25 (1), 2005Natural Areas Journal 25:10–18•Plant Communities Growing on Boulders in the Allegheny National Forest: Evidence for Boulders as Refugia from Deer and as a Bioassay of OverbrowsingWalter P. Carson1,3Joshua A. Banta1,4Alejandro A. Royo1,2Chad Kirschbaum21University of PittsburghDepartment of Biological SciencesA 234 Langley HallPittsburgh, PA 15260, [email protected] Northeastern Research StationWarren, PA 16365, USA•R E S E A R C H A R T I C L E3 Corresponding author: [email protected]; 412-624-54964 Current address: Dept. of Ecology and Evolution, 650 Life Sciences Bldg., State University of New York at Stony Brook, Stony Brook, NY 11794. E-mail [email protected]: Deer have been overabundant throughout much of Pennsylvania since at least the 1940’s. We compared plant communities in the Allegheny National Forest (ANF) on boulder tops and the forest floor to test the hypothesis that large boulders serve as refugia for plants threatened by deer herbivory. Five of the ten most common woody species (hemlock, Tsuga canadensis L., mountain maple, Acer spicatum Lam., red maple, A. rubrum L., striped maple, A. pensylvanicum L., and yellow birch, Betula alleghaniensis Britton) occurred at much higher densities on boulders than in randomly selected areas of the same size adjacent to these boulders on the soil surface. We never encountered any individuals of hemlock, mountain maple, or red maple on the forest floor. Total woody species density (excluding root suckers of beech, Fagus grandifolia Ehrh.) was nearly three times higher on the boulders. Woody species richness and evenness, as well as forb and shrub cover and richness, were also much greater on boulders. Our results strongly suggest that overbrowsing by deer can dramatically reduce tree regenera-tion and diversity as well as reduce forb and shrub abundance in the ANF. Furthermore, understory plant communities are now dominated by species that are known to be unpalatable or tolerant of deer browse, particularly beech, grasses, and ferns (Dryopteris carthusiana Vill. and Thelypteris noveboracensis L.). The primary alternative explanation is that conditions on the surface of boulders are superior for numerous woody and herbaceous species. Although we cannot rule this out, we consider this alternative improbable because of the poor nature of these habitats. Because deer are reducing the diversity and abundance of both woody and herbaceous species, we conclude that deer are damaging the very nature of these hardwood forests. Furthermore, our findings suggest that boulders could serve as an inexpensive bioassay of deer impact on vegetation whenever they are common and large enough. Boulders may also overcome the problem associated with the ghost of herbivory past, whereby plant species that would respond to the reduction of herbivores are absent because they have been driven to very low abundance or local extirpation. Our findings suggest that sampling the surface of boulders circumvents this problem because the vulnerable species were never subjected to sustained browsing on these refugia; consequently, these areas may represent typical levels of abundance of these vulnerable plant species.Index terms: beech, browsing, ferns, forest regeneration, herbivory, herbs, refugia, species richness, white-tailed deerable and palatable species to deer refugia though only a small number of these refu-gia have been documented. For example, following a tornado blowdown in the Al-legheny National Forest (ANF), Long et al. (1998) found that hemlock saplings and seedlings were larger and more abundant on tree tip-up mounds compared to areas on the forest floor. They showed that large tip-up mounds were less accessible to deer, and thus were one of the few sites with abundant hemlock regeneration. They acknowledged that tip-up mounds might enhance the growth and density of hemlocks; however, this appeared unlikely because mounds experience dramatic ero-sion, freezing, and desiccation; conditions typically inimical to hemlock germina-tion and survival (Long 1998; see also Schopmeyer 1974, Beatty 1984, Godman and Lancaster 1990, Peterson et al. 1990). Grisez (1960) showed that browsing dam-age was lower and overall woody seedling density (subtracting beech) higher within piles of hardwood slash (leftover from INTRODUCTIONThere is growing evidence that browsing by high populations of white-tailed deer (Odocoileus virginianus) can dramatically reduce the diversity, abundance, and vigor of both woody and herbaceous species in eastern deciduous forests (Miller et al. 1992, Balgooyen and Waller 1995, Waller and Alverson 1997, Augustine and Frelich 1998, Webster et al. 2001, Collins and Carson 2003, Horsley et al. 2003, and a review by Russell et al. 2001). In the Allegheny National Forest (ANF), over-abundant deer substantially reduce


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