Allegheny Highlands forests
The Allegheny Highlands forests are a distinctive biome located in the northeastern region of North America, primarily across Pennsylvania and New York. Characterized by a temperate to boreal climate, these forests are predominantly composed of Eastern hemlock and American beech trees, which together constitute about 60% of the forest's overstory. The biome features a mix of glaciated and unglaciated landscapes that influence its unique vegetation distribution, including a variety of associated tree species like sugar maple, red maple, and black cherry.
Historically, extensive logging in the early 20th century significantly reduced the forest's range, leading to a decline in the populations of dominant species due to threats such as the hemlock woolly adelgid and beech bark disease. Today, conservation efforts are critical for preserving the remaining relict pockets of these forests, which now occupy less than 1% of their original area. The rich biodiversity includes various mammals, birds, and plant species, underscoring the ecological importance of the region. However, human activities, such as urban pollution and natural gas extraction, pose ongoing threats to the health and sustainability of the Allegheny Highlands forests, making their conservation increasingly urgent.
Allegheny Highlands forests
- Category: Forest Biomes.
- Geographic Location: North America.
- Summary: The Allegheny Highlands are home to a series of unique forest flora and fauna, dominated by Eastern hemlock and American beech, found throughout the Allegheny Plateau of Pennsylvania and New York State.
The Allegheny Highlands forests are a temperate to boreal hardwood biome composed largely of two dominant tree species: the Eastern hemlock (Tsuga canadensis) and American beech (Fagus grandifolia), and this forest type is well represented in the Allegheny National Forest. Much of this forest was cleared in the early 20th century, leaving relict pockets throughout northeastern Pennsylvania. Logging left behind large piles of slash and debris, which piled up and led to catastrophic fires that tended to promote early-successional species such as aspen rather than late-successional species like Eastern hemlock. Because this forest is now restricted to such a small area—less than 1 percent of its original range—careful attention should be focused on conservation strategies.
The topography of this biome is characterized by both glaciated and unglaciated sections, which in turn influence the distribution and composition of the vegetation. The glaciated section's bedrock is composed of sandstone, siltstone, and shales; this topography features rounded hillsides, ridges, and valleys. The unglaciated section contains sharper topographic relief; the bedrock is similar but also includes limestone parent material.
The Allegheny Highlands forest community is found in the Allegheny Plateau in New York and Pennsylvania, specifically in the mountain ranges of the Catskills, Poconos, Finger Lakes, Allegheny, and Appalachians. Also found here are some unusual habitats such as high-elevation wetlands and shale barrens. The climate, characterized by warm summers and cool winters, is considered to be a humid continental climate. The soils are largely acidic, which is preferential for hemlock and beech tree species, and have thick organic layers that decompose slowly.
Vegetation Community
The two dominant tree species—Eastern hemlock and American beech—compose roughly 60 percent of all forest overstory tree species within the Allegheny Highlands forests. Eastern hemlock is the most common tree species in approximately 2,471,054 acres (1 million hectares) of forest from the southern Appalachian Mountains north into southern Canada and west to the Great Lakes region. Strikingly, this abundant species is disappearing rapidly (within decades across its entire range) due to infestation by an exotic pest: the hemlock woolly adelgid (Adelges tsugae). Hemlock is a late-successional tree and an irreplaceable foundation species (a type of species that is the dominant primary producer in an ecosystem).
American beech is a shade-tolerant species that is slow-growing and prefers moist, well-drained acidic soils, making it a complementary species to the acidic environment commonly associated with the Eastern hemlock. American beech provides an important food source—beechnuts—for a variety of wildlife species. American beech is currently threatened by the beech bark disease complex, which is leading to a decline in its abundance and importance within the Allegheny Highlands forests.
Associated vegetation forest types include sugar maples (Acer saccharum), which in some parts will replace Eastern hemlock as the dominant overstory species, leading to beech–maple stands, which are more commonly found in drier soils. Associated tree species within the Allegheny Highlands include red maple (Acer rubrum), yellow birch (Betula allegheniensis), black birch (Betula lenta), white ash (Fraxinus americana), and black cherry (Prunus serotina). These associated species are found both in hemlock–beech stands and beech–maple stands, and generally are indicative of nutrient-rich soils.
In the 21st century, the Allegheny forests where this relict forest community still exists are more often composed of black cherry and maple trees than of the hemlocks and beeches that dominate the Allegheny Highlands. The understory community within these forests largely consists of shade-tolerant herbaceous species such as Canada mayflower (Maianethemum canadense), partridgeberry (Mitchella repens), wintergreen (Gaultheria procumbens), and lady's slipper (Cypripedium acaule), accompanied by hardy ericaceous shrubs such as mountain laurel (Kalmia latifolia) and highbush blueberry (Vaccinium corymbosum).
Important Biota
The Allegheny Highlands support a wide variety of terrestrial and aquatic organisms. Important plant species include Fraser's marsh, St. John's wort (Triadenum fraseri), bunchberry (Cornus canadensis), Catawba rhododendron (Rhododendron catawbiense), and the flame azalea (Rhododendron calendulaceum).
The forest is home to a variety of mammals, including the black bear (Ursus americanus), snowshoe hare (Lepus americanus), red and gray fox (Vulpes vulpes, Urocyon cinereoargenteus), beaver (Castor canadensis), mink (Neovison vison), and muskrat (Ondatra zibethicus). The white-tailed deer has played an important role in the development of the Allegheny Highlands forest after logging and has strongly influenced the trajectory of succession and community structure by browsing preferentially. The timber rattlesnake (Crotalus horridus) is among the larger of many reptilian species supported by the Allegheny Highlands forest. A suite of avian species depends on this forest for vital habitat and food resources, including migratory songbirds such as thrushes (Catharus spp.), warblers (Dendroica spp.), and raptors (Accipitor spp.). This forest also provides important habitat for insects including dragonflies, damselflies, moths, and butterflies.
Special Features
The Allegheny Highlands are home to several unique places worth trekking out to, including several nationally designated areas such as the Hickory Creek Wilderness, the Allegheny Islands Wilderness, the Allegheny and Clarion Wild and Scenic Rivers, the Allegheny National Recreation Area, the North Country Scenic Trail, and Buzzard Swamp. The Allegheny National Forest encompasses a variety of topographic features, and its protection ensures the protection of a vital watershed within the Allegheny region, thus promoting the protection of animal and plant communities that live within that region.
Human Threats
Humans can be a threat to the health and maintenance of the Allegheny Highlands forests. Over the past century, the landscape was transformed, initially due to logging, then by targeted conservation efforts such as the Civilian Conservation Corps, and more recently by development. People have increased the habitat fragmentation within this forest due to road construction, development for recreational activities, and forest management for wood products. Furthermore, pollution from urban centers such as Chicago and Cleveland travels eastward toward the Allegheny Highlands, negatively influencing plant and animal health and community resilience to environmental disturbances. The most recent harsh stress comes from the rush to drill and apply hydrofracture techniques to extract natural gas from the Marcellus Shale formation that underlies much of this biome.
Global climate change, induced by anthropogenic pollution over large scales, will also have devastating effects on this ecosystem as the vegetation and animal communities are exposed to unprecedented climate regimes, which will likely lead to species displacement over the long term; a warmer climate also leads to longer windows of seasonal opportunity for invasive insects and their linked bacterial and fungal disease threats.
Bibliography
Braun, E. Lucy. Deciduous Forests of Eastern North America. Caldwell, NJ: Blackburn Press, 1950.
Eyre, F. H., ed. Forest Cover Types of the United States and Canada. Bethesda, MD: Society of American Foresters, 1980.
"Forest Health Monitoring in Alleghany Portage Railroad National Historical Site." National Park Service, 22 Jan. 2020, www.nps.gov/articles/forest-health-monitoring-in-allegheny-portage-railroad-national-historic-site.htm. Accessed 14 Nov. 2024.
Kudish, Michael. The Catskill Forest: A History. Fleischmanns, NY: Purple Mountain Press, 2000.
Lieb, Lisa C. “Fracking Threatens the Allegheny Plateau and Its Biodiversity.” The Revelator, 27 Mar. 2023, therevelator.org/fracking-allegheny-biodiversity/. Accessed 14 Nov. 2024.