tsLandscape and Urban Planning, 23 (1994) 47-53 47Elsevier Science B.V., Amsterdam

Deer and diversity in Allegheny hardwood forests: managing an

unlikely challenge

David S. deCalestaNortheastern Forest Experiment Station, USDA Forest Service, PO Box 928, Warren, PA 16365, USA

Abstract

High white-tailed deer ( Odocoileus virginianus) density and interfering vegetation were identified as factors affectingthe regeneration of hardwood forests in the Allegheny National Forest and surrounding forests in northwestern Pennsyl-vania. Research was designed by Forest Service scientists to quantify these effects. A high degree of interest in the impactof these effects on the diversity of forest resources led to additional research. Scientists, natural resource managers, andprivate timber interests used the research findings on the impacts of deer and interfering ve getation on regeneration anddiversity to produce newsletters, tours, symposia, and to make presentations to groups of legislators, environmentalistsand other influential segments of the public. This combined research–educational effort has been associated with theenactment of hunting regulations designed to reduce deer density and for registration and continued use of herbicides tocontrol interfering vegetation. Both actions have the potential to increase the diversity of songbirds and woody and her-baceous vegetation in forest lands. The challenge is to sustain directed management of deer density and interfering vege-tation until these factors are controlled to the point where they no longer negatively impact the diversity of forest resources.

1. Introduction 1991 from the four-county area encompassingthe ANT. In addition to its directive to manage

The Allegheny National Forest ( A_NF ) is lo- for multiple resources, the ANF is charged tocated in northwestern Pennsylvania, and corn- "provide for and maintain diversity of plantprises approximately 250 000 ha of Allegheny and animal communities to meet overall mul-hardwood, northern hardwood, and oak tiple-use objectives".( Quercus sp. ) types. It is the second largest The ANF and its resources have changedpiece of contiguous public land in Pennsylva- since the land was developed by European set-nia and the second largest national forest in the tlement. With the exception of a few isolatednortheastern United States. Like other na- patches of old growth forest, the ANF was al-tional forests, it is managed for multiple re- most completely logged in a, sequence of par-sources. It provides approximately one-third of tial cuts and clearcuts during the 1890-1930the world's supply of cherry veneer and furni- railroad logging era in the northeast and inLure wood and generates over 14 million dol- Pennsylvania (Braun, 1964; Marquis, 1975 ).lars annually from timber receipts, special use As a result of this activity species were lost.permits, recreation fees, power and mineral Some of the native flora and fauna were elim-fees, and administrative user fees. The ANF's inated, either deliberately, e.g. the mountainabundant natural resources attract thousands lion ( Felis concolor) and the wolf ( Canisof recreationists annually (335 000 recreation pus), or inadvertently, e.g. American chestnutvisitor-days in 1990) (Allegheny National ( Castenea dentata), passenger pigeon ( Estop-Forest, 1990 ). Chief among these are hunters istes migratorius) and eastern elk ( Cervzts ela-who harvested over 32 000 white-tailed deer in phus canadensis) (Schorger, 1955; Genoways,

© 1994 Elsevier Science B.V. .A/1 ri ghts reserved 0169-2046/94/307.00

55D/ 0169-2046 (93) 03007-V

48 D.S. deCalesta / Landscape and Urban Planning 28 (1994) 47-53

1985). The composition of overstory trees to colonization (Witmer and deCalesta, 1992).shifted from a climax mix of beech ( Fagus The heavy browsing pressure exerted by deergrandifolia )–su2-ar maple (Acer saccharum)– for approximately 70 years resulted in the losshemlock ( Tsuga canadensis) to an early to or a reduced abundance of some woody spe-mid-successional mix of black cherry (Prunus cies, shifts in species composition of unders-serotina )–beech–red maple (Acer rubra) tort' vegetation, and failure of regeneration in( Marquis and Gearhart, 1983 ). The oak type areas with excessively hi gh deer densitiesforest, a temporary type on the Alle gheny Pla- (Marquis and Brenneman, 1981; Whitney,teau created by disturbances such as fire, is 1984 ). Understory herbaceous ve getation andshrinking as these disturbances are no longer shrubs, including Rubus and witch hobble ( Vi-common. burnum almfolium), were nearly eliminated by

Prior to European settlement, which oc- deer and replaced by ferns and grasses (Hough,curled in the ANF area about 1800, lar ge-scale 1965; Horsley and Marquis, 1983; Whitney,perturbations (windstorms and tire) pro- 1984). When understories are dominated byduced large even-age blocks (thousands of grasses and ferns and high deer densities pro -hectares) of shade-intolerant tree species at in- duce heavy browsing intensity, a diverse woodyfrequent intervals (100-300 years) (Borman vegetation, fails to become established (Hor-and Likens, 1979 ). Smaller openings created slew and Marquis, 1983), and future forests arein the forest by ice storms, local wind shear, characterized by low tree species diversity.and insect- and disease-induced mortality of The demands of deer hunters (seeing asindividual trees comprised approximately 1% many deer as possible during the huntin g sea-of the forest annually (Runkle, 1982). These son and high hunter success rates) can be metpatches of large and small openings created only when deer density is so high that vegeta-varying amounts of forage for deer and pro- tion damage becomes chronic.vided upper limits to deer density. Deer den- These challenges to the preservation of di-sities approaching these limits were dampened. versify on the ANF are lon g-standing and wereby pressure from abundant predators (Ameri- created in part by societal demands for forestcan Indian, mountain lion, wolf) (Ellingwood resources (deer and timber) that run counterand Caturano, 1988; Witmer and deCalesta, to maintaining diversity. The ecolo gical rela1992 ) tionships between these resources were incom-

This system of forage and predator influence pletely understood by forest managers andon deer density was eliminated during the late those who influence and make decisions about1800s as white settlers engaged in unregulated the management of forest resources. This pa-market hunting to meet a growing demand for per describes the association developed be-meat in large cities and lo gging camps. White- tween natural resource scientists and man-tailed deer were nearly extirpated from Penn- agers to develop solutions to preservingsylvania by the end of the 19th century (Mar- diversity on the ANF.quis, 1975 ). Subsequent prohibition of hunt-ing, elimination of natural predators, and 2. Development of the research programcreation of a vast abundance of deer forage byharvesting Pennsylvania's forests in the late In 1979 the silvicultural research work unit1800s and early 1900s resulted in a steep in- ( RWU-4l52 ) of the USDA Forest Servicecrease in the number of deer, beginning in Northeastern Forest Experiment Station de-1907. Although the deer population has sub- signed a series of research projects to "developsequently declined, the overall number of deer and refine silvicultural practices required toremains far above the density that existed prior establish and grow high quality hardwood for-

D.S. deCaiesta i Landscape and Urban Planning 28 (1994)47-53 49

ests for timber and wildlife" on the Allegheny density on the diversity of forest vegetation,Plateau and Allegheny Mountain sections of including, woody and herbaceous vegetation,Pennsylvania, New York, Ohio, and West and wildlife communities, including, songbirds

irginia. and small mammals ( deCalesta, 1992 ).Representatives from the USDA Forest Results from this study indicated that deer

Service, timber industry, Pennsylvania Game density was negatively related to the success ofCommission, Pennsylvania Bureau of For- hardwood re generation, and diversity of woodyestry, regional universities, and New York State and herbaceous vegetation and songbirds nest-Conservation Department participated in the ing in sapling- and pole-sized trees. The resultsProcess of identifying major factors limiting the also suggested that the threshold deer densitysuccessful regeneration and yields of hard- where these effects became limitin g, was be-wood trees and designing appropriate research tween 4 and 8 deer km-2 . At deer densities ofprojects. High deer density and interference over 8 deer km', selective browsing by deerfrom woody and herbaceous vegetation were altered the species composition of woody andamong the top priority items identified. A herbaceous vegetation so that plant-plant re-number of studies was established to deter- lationships changed, altering patterns of corn-mine the impacts of these independent vari- petition for resources among plant species andables on regeneration success. Because deer and reducing the diversity of woody and herba-interfering vegetation were later identified as ceous species ( deCalesta, 1992 ).factors potentially affecting the diversity offorest resources, evaluation of the impact of 3.2. Impact of interfering vegetation on diversitythese factors on the diversity of forest re-sources was conducted.

Earlier studies suggested that ferns, grasses,3. Applied research projects striped maple (Ater pennsylvanicum), and

beech can interfere with the regeneration of3.1. Impact of deer density on diversity other woody plants, especially when high deer

densities reduce the abundance of these woodyIn 1979, a 10 year project was initiated to plants (Horsley, 1977, 1981; Horsley and

investigate the relationship between deer den- Bjorkbom, 1983; Horsley and Marquis, 1983 ).situ and hardwood regeneration (Tilghman, At sufficiently high levels of interference, de-1989 ) . Five different deer densities (0, 3.7, 7.9, sirable woody species do not become estab-19.9 and 24.9 deer km-2 were simulated lished in fully stocked conditions when overs-within four replicate enclosed sites. Within tory trees are removed by timber harvest.each deer density enclosure, 10% of the area Instead, understocked stands of primarily un-was clearcut, 30% thinned, and 60% left uncut desirable woody and herbaceous species result.to simulate intensive management to sustain Subsequent studies determined that the ju-timber yield on a 100 year rotation. The origi- dicious use of herbicides could reduce herba-nal dependent variable for this study was the ceous and woody plant interference suffi-success of hardwood regeneration as measured ciently to permit the successful regeneration ofby regeneration stocking percentage, height desirable woody plants (Horsley, 1982; Hor-arowth, and maintenance of desirable woody slew and Bjorkbom, 1983 ). The timing of ap-species composition. plication and lack of residual effect of herbi-

Increased interest and emphasis on manage- cides prevented the exposure of forbs thatmeat for diversity of forest resources prompted flower in spring and early summer (Horsley,an 1 1 th year evaluation of the impact of deer 1992 ). Because herbicides did not totally

50 D.S. deCalesta /Landscape and Urban Planning 28 (1994) 47-53

eliminate target herbaceous and woody plants ties below levels where habitats are negativelyfrom treated sites, herbicide use actually in- impacted (McShea and Rappole, 1992; de-creased the diversity of forest floor ve getation Calesta, 1994) .( Horsley, 1992). A committee was formed by organizers of the

The sum of these studies has been a qualita- deer research to educate and inform key deci-tive and quantitative description of the im- sion-makers and influential action groupspacts of deer and interfering vegetation on the about the impacts of deer on forest resources.diversity of woody and herbaceous vegetation The goal of the committee was to "promoteand selected wildlife communities in hard- enactment of deer hunting regulations that willwood forests on the Allegheny Plateau of west- bring the deer herd down to target levels rec-ern Pennsylvania. The studies were estab- ommended by the Pennsylvania Game Com-lished as a direct result of the request for mission, as these levels approximate densitiesinformation about these impacts from practis- associated with successful forest regenerationing, foresters representing public and private and maintenance of diversity of naturalforest lands. Implementation of the manage- resources".meat steps required to miti gate these impacts Committee members developed and dis-on the diversity of forest resources required a seminated a newsletter to persons consideredconcerted educational effort conducted by re- influential in setting deer huntin g regulations.search and management personnel. Results from research developed by the com-

mittee, as well as research conducted by oth-4. Applying research results ers, were summarized to promote the idea of

deer herd reduction. Quantitative descriptionsApplying the knowledge obtained from the of the negative impact of high deer densities

studies required informing persons in posi- on commercial forestry and on the diversity oftions of authority about the research implica- forest resources were included. Suggestionstions and the consequences of acting on these were aired on how deer hunting regulationsresults. A major effort was undertaken to edu- could be managed to effect desired deer herdcate these decision-makers concerning the reductions,management steps required to counteract the Committee members conducted tours of re-negative impacts of deer and interfering vege- search sites to demonstrate the negative im-tation on forest resources and their diversity. pact of high deer density on forest resources.

Decision-makers and special interest audi-4.1. Deer management ences were targeted as tour participants. Com-

mittee members testified before state senateA considerable body of knowledge concern- and house committees that influenced deci-

ing the impact of deer damage on vegetation sions on deer harvest regulation. Committeeuniformly concludes that the best, most cost- members organized and conducted two largeeffective method for reducing deer damage is symposia that featured the results of studies ofto reduce deer densities to levels that do not deer impact on forest resources. With these ef-threaten the integrity of vegetative communi- forts, the committee obtained media coverageties (Matschke et al., 1984; Ellingwood and to spread further the message of deer impacts.Caturano, 1988; Witmer and deCalesta, 1992 ). To enhance the efficiency of its message, theBecause deer impact wildlife communities in- committee aligned itself with agricultural in-directly via their impact on vegetation, the best terests (another group affected by high deerway to lessen the negative impact of deer on density) to provide a united front that repre-wildlife communities is to reduce deer densi- sented two large constituencies and considers-

D.S. deCalesta / Landscape and Urban P!anning 28 (1994) 47-53 51

ble portions of Pennsylvania's economy.In 1989, pressurized by these groups to re-

duce deer density to its own target density (7deer km' in the four-county area surroundingthe ANF), the Pennsylvania Game Commis-sion embellished its burgeoning antlerless deerharvest program by initiating a bonus tag sys-tem which allowed hunters to harvest an addi-tional deer. Deer harvest, numbers of antler-less deer tags, and bonus tags increased in thesucceeding 1990-1992 seasons and the densityof the overwinter deer herd stabilized; previ-ously it had been climbing steadily in spite ofincreased harvest. Recalculation of deer den-sity for 1991-1992 by Pennsylvania GameCommission personnel su ggested that it ac-tually decreased by about 1.5 deer km' dur-ing 1990-1991 in the four-county area encom-passing the ANF. If this declining trend in deerdensity can be maintained, by 1997 the den-sity will approximate levels that research hasidentified as below the threshold for negativeimpact on diversity of forest resources.

It is unclear how long it will take (given thatdeer density can be kept at or below the targetlevel) for woody and herbaceous vegetation toregain a measure of previous diversity. Prelim-inary results suggest that this period may be 10years for woody vegetation (D.S. deCalesta,unpublished data, 1993; Healy, USDAForest Service, personal communication,1992). Unfortunately, herbaceous vegetationparticularly forbs, have much lower seed dis-persal distances than trees, and unlike trees, nolonger have adult individuals available to shedseed on many sites. Regaining the diversity offorbs may require several decades, duringwhich time deer density is rigorously main-tained at or below target density. Withstand-ing pressure from the hunting public to in-crease deer density during this period ofdiversity recovery will require sustained, un-remitting effort by a coalition of impactedgroups and enlightened, dedicated agencyprofessionals.

4.2. Vegetation management

The proven efficacy of selected herbicides forthe control of interfering vegetation, with nodemonstrable negative environmental im-pacts, led to registration of these chemicals foruse in forest management (Horsley, 1988 ).However, forest managers were confrontedwith a number of political challenges that couldprevent such use of herbicides to improve di-versity of forest vegetation. Some environ-mental groups threatened to file appeals againstthe Forest Service to challenge the use of her-bicides in resource management; others ac-tually did so.

Administrators from the ANF arranged forinformal meetings among scientists, forestmanagers, and environmental groups wheresuits were pending. Administrators used vege-tation management research to successfully re-but arguments of environmental groups in re-sponse to the Environmental Impact Statementconcerning the use of herbicides.

As a result of the informal meetings, theenvironmental groups refrained from filing suitschallenging the use of herbicides and the con-cerns of other environmental groups were suc-cessfully rebutted. The use of herbicides tocontrol interfering vegetation on the ANT wassuccessfully defended, and today the ANT se-lectively uses herbicides to control interferingvegetation. As a fortuitous result, the diversityof understory woody and herbaceous vegeta-tion is being enhanced (Horsley, 1992).

5. Discussion

Deer density and interfering vegetation af-fect the diversity of woody and herbaceousvegetation and song birds via impacts on com-position, abundance, and structure of vegeta-tion. It is important to recognize that both fac-tors must be managed concurrently to optimizethe diversity of forest resources. Without ag-gressive management, deer density and inter-

52 deCalesta / Landscape and Urban Planning 28 (1994) 47-53

fering plants will increase at the expense of di-

Genoways, H.H., 1985. Mammals. In: H.H. Genoways andF.J. Brenner (Editors), Species of S pecial Concern inversity of forest resources. Pennsylvania. Carnegie Museum of Natural History,

Attempts to educate decision-makers on the Pittsburgh, PA, pp. 355-423.importance of controlling deer density and in- Horsley, S.B., 1977. Allelopathic inhibition of black cherry

terfering vegetation have resulted in the reten- by fern, grass, goldenrod, and aster. Can. J. For. Res.,terfe7:205-216.

tion of the use of herbicides to control interfer- Horsley, S.B., 1981. Control of herbaceous weeds in Alle-ing, vegetation and modest reductions in deer gheny hardwood forests with herbicide. Weed Sci., 29:655-

density. Until deer densities reach target lev- 662.Horsley, 1982. Development of reproduction after her-els, considerable persuasion skills will be re- bicide-clearcut and herbicide-sheiterwood cut treatment

quired to convince decision-makers to con- of Allegheny hardwood stands. Res. Note NE-308, UStinue endorsing aggressive efforts for reducing Department of Agriculture Forest Service.

controlling interferingcontroforanddensity Horsley, S.B., 1988. How vegetation can influence regenera-deertion. In: C.H. Smith, A.W. Perkey and W.E. Kidd, Jr.

vegetation. These activities will need to be (Editors), Workshop Proceedin gs Guidelines for Regen-conducted within landscapes managed by sil- crating Appalachian Hardwood Stands. SAF Publ. 88-03,

vicultural systems that produce mandated US Department of Agriculture Forest Service, pp. 38-55,Horsley, S.B., 1992. Species diversity of Allegheny hardwoodpublic outputs while enhancing the diversity of stands over time after a single application of glyphosate.

forest resources. Proc. Annu. Meet. Northeast. Weed Sci. Soc., 46:137.

The current emphasis of the Forest Service

Horsley, S.B. and Bjorkbom, J.C., 1983. Herbicide treatmentof striped maple and beech in Allegheny hardwood stands.to practice 'Ecosystems Mana gement' reflectsFor. Sci., 29:103-112.

a desire to manage all forest resources in an Horsley, S.B. and Marquis, D.A., 1983. Interference by weedsecologically sound manner. To achieve this and deer with Allegheny hardwood reproduction. Can. J.

end, the Forest Service and other agencies For. Res., 13:61-69.Hough„A.F., 1965. A twenty-year record of understory- vege-

manage public and private forests need to cut tational change in a virgin Pennsylvania Forest, Ecology,through the confrontational rhetoric of such 46:370-373.

groups as deer hunters and. environmental

Marquis, D.A., 1975. The Allegheny hardwood forests ofPennsylvania. Gen. Tech. Rep. NE 15, US Department ofgroups and provide them with clear examplesAgriculture Forest Service.

(from research) of how factors affecting such Marquis. D.A. and Brenneman, R., 1981. The impact of deerforest values as diversity need to be and can be on forest regeneration in Pennsylvania. Gen. Tech. Rep.

managed. NE-65, US Department of Agriculture Forest Service.Marquis, D.A. and Gearhart, P., 1983. Cherry-Maple. In: R.M.

Burns (Editor), Silvicultural Systems for the Major For-References est Types of the United States. Agricultural Handbook 445,

US Department of Agriculture Forest Service, pp. 137-

Allegheny National Forest, 1990. Alle gheny National Forest 140.

Allegheny National Forest, Warren, PA, Matschke, G.H., deCaiesta, D.S. and Harder, J.D., 1984. CropAnnual Report. A , , ,p30 damage and control. In: L.K. Halls (Editor), White-tailedp.

Borman, F.H. and Likens, G.E., 1979. Catastrophic distur- Deer Ecology and Management. Stackpole Books, Harris-

bance and the steady state in northern hardwood forests. burg, pp. 647-654.

Am. Sci., 67:660-669. McShea. W.J. and Rappole, J.H., 1992. White-tailed deer asBraun. E.L., 1964. Deciduous Forests of Eastern North keystone species within forested habitats of Virginia. Va.

America. Hafner, New York, 596 pp. J. Sci., 43:177-186.deCaiesta, D.S., 1992. Impact of deer density on species di- Runkle, J.R., 1982. Patterns of disturbance in some old-growth

versity of Allegheny Hardwood Stands. Proc. Annu. Meet. mesic forests of eastern North. America. Ecology, 63:1533-Northeast. Weed Sci. Soc., 46:135. 1546.

deCalesta. D.S., 1993. impact of deer density on diversity of Schorger, A.W., 1955. The Passenger Pigeon. University ofsongbirds in northwestern Pennsylvania. J. Wildl. Man- Wisconsin Press, Madison, 424 pp.age.. in press. Tilghman, N.G., 1989. Impacts of white-tailed deer on forest

Ellingwood, M.R. and Caturano, S.L., 1988. An evaluation of regeneration in northwestern Pennsylvania. J.deer management options. Connecticut Department of Manage., 53:524-532.Environmental Protection, Wildlife Bureau, Hartford, 12 Whitney, G.G., 1984. Fifty years of change in the arborealpp. vegetation of Heart's Content, an old-growth hemlock-

D.S. deCaiesta /Landscape and Urban Planning 28 (1994) 47-53 53

white pine-northern hardwood stand. Ecology, 65:403- ficuity of bringing the Pennsylvania deer herd under con-408. trol. Proc. East. Wail. Damage Control Conf., 5:130-137.

Witmer, G.W. and deCalesta, D.S., 1992. The need and dif-

K

Reprintedfrom

An International Journal of Landscape Ecology , Landscape Planning and Landscape Design

Landscape and Urban Planning, 28 (1994) 47-53Elsevier Science B.V., Amsterdam

Deer and. diversity in Allegheny hardwood forests: managing anunlikely challenge

David S. deCalestaNortheastern Forest Experiment Station, USDA Forest Service, PO Box 928, Warren, PA 16365, USA

ELSEVIER

An International Journal of Landscape Ecology, Landscape Planning, and Landscape Design

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incl. PostageISSN 0378-1127

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FOREST ECOLOGYAND MANAGEMENT

An International Journal

Editors-in-Chief:E.P. Farrell, Environmental Resource Management, University College Dublin,

Beifield, Dublin 4, IrelandR.F. Fisher, Department of Forest Science, Texas A & M University,

College Station, TX 77843-2135, USA

Founding Editor: L.L. Roche, Murroe, Ireland

Book Review Editor: D. Binkley, Forest and Wood Science, Colorado State University,Fort Collins, CC 80523, USA

AIMS AND SCOPEForest Ecology andManagement publishes

scientific articlesconcerned with forestmanag ement andconservation and inparticular, the application ofbiological, ecological andsocial knowledge to themanag ement of naturaland man-made forests.The scope of the journalincludes all forestecosystems of the world. Arefereein g process ensuresthe quality and internationalinterest of the manuscriptsaccepted for publication.The journal aims toencourag e communicationbetween scientists indisparate fields who sharea common interest inecolog y and naturalresource management,and to bridge the gapbetween research workersand forest :manag ers in thefield to the benefit of both.