University of Pittsburgh
OP-10: Biodiversity

The original research site for the University of Pittsburgh's Pymatuning Laboratory of Ecology since 1949 is situated on Sanctuary Lake, a protected waterway. It as well as the associated researcher housing site are on the shores of Pymatuning Lake and are completely surrounded by Pymatuning State Park. The Pymatuning Lab also manages Tryon-Webber Woods, an old growth forest owned by the Western Pennsylvania Conservancy.

The impact of deer on relationships between tree growth and mortality in an old-growth beech-maple forest Zachary T. Long *, Thomas H. Pendergast IV, Walter P. Carson White-tailed deer have been at high levels in the northeastern forests of the United States for decades and have strongly influenced forest dynamics. In this long-term study, we found that the composition of the overstory and understory assemblages of an old-growth beech-maple forest differed significantly. We used exclosures to test the hypothesis that deer contributed to these differences by differentially influencing the relationship between growth and mortality among seedlings of the six most abundant tree species. In the absence of deer, we found that the mortality of the six species decreased with increased growth and that interspecific differences in the relationships between growth and mortality coincided with previously observed shade-tolerance rankings. In the presence of deer, mortality decreased with growth only for the browse tolerant species (American beech, black cherry, and sugar maple). Mortality did not decrease with growth for preferred browse species (oak species, ash species, and red maple), rather, this relationship was eliminated in the presence of deer. The changes in growth and mortality relationships in the presence of browsing generally corresponded to observed changes in seedling density following the removal of deer. Sugar maple, ash, black cherry, and total stem density increased in the absence of deer. Our results suggest that the relationship between survival and growth in the understory, a metric of shade tolerance, is a fairly plastic response that varies depending upon the presence and absence of herbivores. Our results indicate that deer have contributed to the differences between understory and overstory vegetation, with browse tolerant species increasing in abundance at the expense of preferred browse species. The legacy of deer overabundance: long-term delays in herbaceous understory recovery Thomas H. Pendergast IV, Shane M. Hanlon, Zachary M. Long, Alejandro A. Royo, and Walter P. Carson Decades of white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) overpopulation have dramatically homogenized forests across much of the eastern United States, creating depauperate forest understory communities. The rate at which these communities recover once deer browsing has been reduced remains an open question. We evaluate overbrowsing legacy effects by examining how forest herbaceous layers respond in terms of biodiversity, density, and community composition over 11 years using exclosures and control plots within a mature beech–maple forest. Although little recovery occurred in the first 5 years, total density and preferred browse density rebounded substantially during the final years of the study. Although community composition began to diverge between exclosure and control plots after 5 years, diversity failed to recover even after 11 years of excluding browsers. Our findings show that vulnerable species can increase after excluding browsers but only if those species were initially present. Biodiversity recovery may be extremely slow because preferred browse species have been nearly extirpated from many forests and thus are unable to recruit into refugia. We empirically demonstrate the extent of the ghost of herbivory past or legacy effect of browsing, i.e., the substantial time delay between herbivore abatement and community response after decades of high deer densities.

Tryon-Weber Woods Species List Common Name Scientific name Multiflora rose Rosa multiflora American hophornbeam Ostrya virginiana Apple Malus sp. Arrowhead viola Viola hastata Black cohosh Actaea racemosa Ash Fraxinus sp. American beech Fagus americana Perfoliated bellwort Uvularia perfoliata Blueberry Vaccinium sp. Black birch Betula lenta Black cherry Prunus serotina Blackgum Nyssa sylvatica Buttercup Ranunculus sp. American cancer-root Conopholis americana Cherry Prunus sp. Christmas fern Polystichum acrostichoides Cinnamon fern Osmunda cinnamomea Cleaver Galium sp. Clubmoss Huperzia lucidula Gooseberry Ribes sp. Flowering dogwood Cornus florida American elm Ulmus americana False Solomon's seal Maianthemum racemosum Garlic mustard Alliaria petiolata Grapevine Vitis sp. Grass Poaceae Hawthorne Crataegus sp. Hay-scented fern Dennstaedtia punctilobula Hickory Carya sp. Jewelweed Impatiens capensis Jack-in-the-pulpit Arisaema triphyllum Japanese barberry Barberis thunbergii Common clubmoss Lycopodium clavatum Mapleleaf viburnum Viburnum acerifolium Mayapple Podophyllum peltatum Canada maylilly Maianthemum canadense Cucumber magnolia Magnolia acuminata New York fern Thelypteris noveboracensis Devil's walkingstick Aralia spinosa Partridgeberry Mitchella repens Poplar Populus sp. Broad-leaved plantain Plantago rugelii Poison ivy Toxicodendron radicans Red maple Acer rubrum Red oak Quercus rubra Raspberry Rubus sp. Sassafras Sassafras albidum Sedge Cyperaceae Sensitive fern Onoclea sensibilis Serviceberry Amelanchier sp. Sessile bellwort Uvularia sessilifolia Solomon's seal Polygonatum pubescens Spicebush Lindera benzoin Sugar maple Acer saccharum Trillium (at least 3 species) Trillium spp. Tulip poplar Liriodendron tulipifera Canada white violet Viola canadensis Roundleaf yellow violet Viola rotundifolia Common blue violet Viola sororia Virginia creeper Parthenocissus quinquefolia White oak Quercus alba American witch hazel Hamamelis virginiana Wood fern Dryopteris sp. Fourleaved yam Dioscorea quaternata Eastern Newt Notophthalmys viridescens Northern Dusky Salamander Desmognathus fuscus Mountain Dusky Salamander Desmognathus ochrophaeum Northern Two Lined Salamander Eurycea bislaneata Redback Salamander Plethodon cinereus Slimy Salamander Plethodon glutinosis Northern Red Salamander Pseudotriton ruber Wood Frog Lithobates sylvaticus Spring peeper Pseudacris crucifer Green frog Lithobates clamitans Eastern American Toad Anaxyrus americanus Four-toed Salamander Hemidactylium scutatum Spring Salamander Gyrinophilus porphyriticus Spotted Salamander Ambystoma maculatum Fowler's Toad Anaxyrus fowleri Gray Treefrog Dryophytes versicolor Wood Duck Aix sponsa Wild Turkey Meleagris gallopavo Turkey Vulture Cathartes aura Red-tailed Hawk Buteo jamaicensis Red-shouldered Hawk Buteo lineatus Mourning Dove Zenaida macroura Yellow-billed Cuckoo Coccyzus americanus Black-billed Cuckoo Coccyzus erythropthalmus Eastern Screech-Owl Megascops asio Great Horned Owl Bubo virginianus Barred Owl Strix varia Chimney Swift Chaetura pelagica Ruby-throated Hummingbird Archilocus colubris Red-bellied Woodpecker Melanerpes carolinus Downy Woodpecker Picoides pubescens Hairy Woodpecker Picoides villosus Northern Flicker Colaptes auratus Pileated Woodpecker Dryocopus pileatus Eastern Wood-Pewee Contopus virens Acadian Flycatcher Empidonax virescens Eastern Phoebe Sayornis phoebe Great Crested Flycatcher Myiarchus crinitus Blue-headed Vireo Vireo solitarius Red-eyed Vireo Vireo olivaceus Blue Jay Cyanocitta cristata American Crow Corvus brachyrhynchos Black-capped Chickadee Poecile atricapilla Tufted Titmouse Baeolophus bicolor White-breasted Nuthatch Sitta carolinensis Brown Creeper Certhia americana House Wren Troglodytes aedon Blue-gray Gnatcatcher Polioptila caerulea Wood Thrush Hylocichla mustelina Veery Catharus fuscescens Swainson’s Thrush Catharus ustulatus American Robin Turdus migratorius Gray Catbird Dumetella carolinensis Brown Thrasher Toxostoma rufum European Starling Sturnus vulgaris Cedar Waxwing Bombycilla cedrorum Ovenbird Seiurus aurocapillus Louisiana Waterthrush Parkesia motacilla Black-and-white Warbler Mniotilta varia Blue-winged Warbler Vermivora pinus Tennessee Warbler Oreothlypis peregrina Nashville Warbler Oreothlypis ruficapilla Hooded Warbler Setophaga citrina American Redstart Setophaga ruticilla Black-throated Blue Warbler Setophaga caerulescens Magnolia Warbler Setophaga magnolia Blackburnian Warbler Setophaga fusca Yellow Warbler Setophaga petechia Yellow-rumped Warbler Setophaga coronate Chestnut-sided Warbler Setophaga pensylvanica Black-throated Green Warbler Setophaga virens Blackpoll Warbler Setophaga striata Eastern Towhee Pipilo erythrophthalmus Chipping Sparrow Spizella passerina Song Sparrow Melospiza melodia Northern Cardinal Cardinalis cardinalis Scarlet Tanager Piranga olivacea Rose-breasted Grosbeak Pheucticus ludovicianus Indigo Bunting Passerina cyanea Common Grackle Quiscalus quiscala Red-winged Blackbird Agelaius phoeniceus Brown-headed Cowbird Molothrus ater Baltimore Oriole Icterus galbula House Finch Carpodacus mexicanus American Goldfinch Carduelis tristis House Sparrow Passer domesticus

On April 19, 2017, the Western Pennsylvania Conservancy (WPC) announced the protection and addition of 18 acres of land in Sadsbury Township, Crawford County, to one of the most ecologically important forested areas in the region. These acres are now part of the Conservancy’s Tryon-Weber Woods Natural Area, which is a remote 108-acre reserve that is open to the public for nature walking, exploring, and hunting. Students from the University of Pittsburgh’s Pymatuning Laboratory of Ecology have been using the natural area for years for a variety of research projects, including learning about the effects of deer browsing on forest health. Protected in May 1976, the natural area consists primarily of upland forest and a small stream valley with hillsides flecked with trillium, violets, bellwort, and wild geranium in spring. A tributary to the stream enters from the east and along the southern border where there is an area of forested wetlands, including vernal pools that provide temporary habitat for some unique plants and animals. The area also contains a 40-acre stand of old-growth American beech-sugar maple forest, thought to be the last remaining mature stand of beech-sugar maple in western Pennsylvania and the easternmost stand in the national range. Accordingly, these woods were recently incorporated into the national Old-Growth Forest Network, which recognizes the locations of and organizations from across the country that protect these special forest types. Some of the trees in this forest are around 100 feet tall and at least 90 to 120 years old. Funds from the estate of Helen B. Katz were used to purchase this property. In 2008, the Conservancy received her bequest that remains the largest contribution to date from an individual to WPC.