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Ecological Benefits of Old-Growth Forests

November 02, 2022 12:00 AM

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​Old-growth forests are undoubtably special and unique places.

Their mostly undisturbed locations are some of the most beautiful to be found, filled with large trees, logs, and snags that are hundreds of years old; an abundance of plant and animal life; an abundance and diversity of lichen and fungus; undisturbed soils; and multi-layered canopies with gaps that result from fallen trees.

These forests look and feel different -- more lush and more green than what you might typically see. You know immediately you are someplace special when setting foot in an old-growth forest.

It is estimated that only a fraction of one percent of the eastern United States’ original forests remain standing -- making these places rare and vitally important to protecting.

Pennsylvania recognizes this and leads the nation in conserving old-growth forests. Currently, Pennsylvania has 25 locations dedicated to the Old-Growth Forest Network.

While these old growth forests are open to the public and beautiful places to visit, even more important is the role they play in biodiversity.

Ecological Benefits of Old-Growth Forests

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All forests are important to a healthy ecosystem; however, old-growth forests are especially important because of their unique structure.

The various canopy layers and berry-producing plants commonly found in old-growth forests are beneficial for many bird species.

In a forest that has not been disturbed for hundreds of years, some trees will develop hollow cavities which become important nesting places for wildlife.

The undisturbed, dead fallen trees create even more habitat for insects, fungi, reptiles, and amphibians.

The moisture within an old-growth forests benefits lichen and mosses, and the species that live among them.

Old-growth forests are one of the few places where topsoil is created instead of destroyed.

Old-growth forests retain more carbon and nitrogen than in forests of other age classes; and are superior for improving water and air quality.

Ecological Benefits of Pennsylvania’s Newly Designated Old-Growth Forests

During the past year, several DCNR locations have been added to the Old Growth Forest Network, including three in Pennsylvania state forests and one in the Pennsylvania state parks network.

Let’s take a look at what makes them special and unique places and what important role they play in biodiversity.

The Hemlocks Natural Area, Tuscarora State Forest

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The most recent addition to the Old-Growth Forest Network, the Hemlocks Natural Area in Perry County encompasses 120 acres of virgin hemlock forest in a narrow ravine about one-half mile long within the 96,000-acre Tuscarora State Forest.

Many of the hemlocks located in the natural area are believed to be more than 225 years old with the largest reaching over 120 feet tall and 50 inches in diameter.

Numerous trees are over 24 inches in diameter. The forest is comprised of a variety of tree species including hemlock, yellow birch, black birch, red oak, red maple, and chestnut oak.

Eastern hemlocks are important in riparian areas (areas that border water bodies) by influencing nutrients and water cycling; and by providing food for stream macroinvertebrate communities.

The trees provide vital winter habitat for numerous wildlife species including deer, ruffed grouse, and wild turkey; as well as seeds feeding many species of songbirds.

Many of the large hemlock trees are still standing in The Hemlocks Natural Area because of treatment against the invasive forest pest, hemlock woolly adelgid.

Beartown Woods Natural Area in Michaux State Forest

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The Beartown Woods Natural Area in Franklin County is 27 acres within the 85,500-acre Michaux State Forest; and is a relic northern hardwood forest more typical of northern Pennsylvania and New England.

Species found in this forest include sugar maple, yellow birch, American beech, and eastern hemlock.

The northern hardwood forest type is more commonly found in the northern part of the state, making it a unique ecological community for the southern portion of the state.

This northern hardwood community is confined to the floodplain associated with Red Run, which bisects the natural area. Despite its small size, Beartown Woods contains a relatively diverse accumulation of native species.

Creek Trail, Boyd Big Tree Conservation Area

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The old-growth area in the Boyd Big Tree Conservation Area in Dauphin County is estimated between 75 and 80 acres; and is located in a small valley on the western boundary of the conservation area.

Ten tree species occur there, including red and white oaks, tulip poplar, beech, hickory, and maple, and understory that includes hemlock, sassafras, mountain maple, striped maple, birch, and witch hazel.

The estimated age of several oaks is 120 years.

Substantial ground level moisture exists at the conservation area, with at least two narrow creeks present in the woods. In the spring, mosses, club moss, princess pine, and ferns appear on the trail’s lower elevations.

There is a notable range of fungi and mushrooms, far greater than in other areas of Boyd Big Tree, providing nutrients to the soil and other plant life -- including a population of a native orchid called Rattlesnake Plantain. The area also is important to a variety of bird species.

When Alexander Boyd donated the conservation area to the commonwealth in 1999, his vision was that most of the area would be an old growth forest someday.

He also wanted a small American chestnut nursery on the property, which was installed. There is a fenced American chestnut research orchard at the conservation area.

Alexander envisioned Boyd to be an old growth stand; and that one day American chestnuts would be part of the mix again.

Sweet Root Natural Area in Buchanan State Forest

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Tucked within Buchanan State Forest, the Sweet Root Natural Area covers 1,526 acres in Bedford County, and is located within Pennsylvania’s Ridge and Valley Ecoregion.

It is one of the few old-growth forests left in Pennsylvania after the clear-cut logging of the 19th and early 20th centuries.

The natural area contains a 69-acre stand of virgin hemlock and cove hardwoods. The rest of the natural area is composed of second growth oak and oak-hard pine stands. 

The Sweet Root Natural Area was designated with special concern for 80 acres of old growth eastern hemlock and unique communities found in the complex topography of the area.

It is best known for its Sweet Root Gap, which is where the old-growth hemlock is located. However, most of the hemlock has been negatively impacted by the invasive forest insect, hemlock woolly adelgid, giving rise to black and yellow birch.

The natural area provides critical habitat for many species of birds, including several warbler species -- 14 species of warblers are species of greatest conservation need.

The area also holds a naturally reproducing population of wild trout and is an Amphibian and Reptile Protection Zone.

What’s Next for Old-Growth Forests in Pennsylvania?

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The Old-Growth Network has a goal is to locate and designate at least one protected forest in every county in the United States. Currently in Pennsylvania, 24 of its 67 counties contain a designated forest in the network.

DCNR will continue to look for additional areas on its state park and forest lands to protect and designate as old growth.

The Pennsylvania Natural Heritage Program is working on understanding the old growth character for Pennsylvania’s forests, and then identifying secondary forests that are attaining this character for protection.

The program is working to map old forests in Pennsylvania and learn more about the plant communities associated with them.

The program also is researching which animal species are markers of an old-growth forest and which aspects of an old forest these species need -- providing further understanding about the important and unique ecological benefits of these special areas.

Learn more about the Pennsylvania Natural Heritage Program’s work on old-growth forests in its most recent newsletter, Wild Heritage News.

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