Dendrology in the Park

 I've put together a short slideshow below outlining some of the tree and shrub species you're likely to encounter out on the trails in Harriman State Park, with a few more details about each species outlined below, enjoy!

Harriman Dendrology by Alicyn Formica 

Introduction:

• Harriman State Park spans approximately 47,500 acres across Orange and Rockland Counties in southeastern New York, making it one of the largest protected forest landscapes in the lower Hudson Valley (New York State Office of Parks, Recreation and Historic Preservation [NYS Parks], n.d.).
• Located within the Appalachian Highlands, the park's glacial history, rugged terrain, and diverse soil types create a wide range of habitats, including oak-hickory forests, northern hardwood forests, wetlands, rocky ridges, and cool hemlock ravines (New York Natural Heritage Program [NYNHP], 2021).
• These forests are dominated by native hardwoods and conifers that provide essential ecosystem services, including wildlife habitat, carbon storage, nutrient cycling, soil stabilization, and water regulation.
• The following species represent some of the most common and ecologically significant trees and shrubs visitors are likely to encounter throughout Harriman State Park.

Northern Red Oak:

• One of the dominant canopy species throughout Harriman's upland hardwood forests (Burns & Honkala, 1990).
• Identified by its pointed, bristle-tipped leaves and mature bark with distinctive vertical "ski track" ridges.
• Produces abundant acorns that are among the park's most important wildlife food resources, supporting black bears, white-tailed deer, wild turkey, squirrels, chipmunks, and numerous songbirds.
• Large mature trees provide nesting habitat, shade, and eventually coarse woody debris that supports insects, fungi, amphibians, and cavity-nesting birds.
• Because northern red oak is relatively drought tolerant, it is expected to remain an important component of northeastern forests as climate conditions continue to change (Iverson et al., 2008).

Chestnut Oak:

• Particularly common on Harriman's dry, rocky ridges where shallow soils limit competition from other hardwood species (Burns & Honkala, 1990).
• Easily recognized by leaves with rounded teeth resembling chestnut leaves and thick, deeply furrowed bark.
• Well adapted to drought and historically benefited from periodic low-intensity fire, making it an important species in Appalachian ridge ecosystems.
• Acorns provide an additional mast source for wildlife and help sustain animal populations during years when other oak species produce fewer seeds.
• Extensive root systems stabilize thin soils on steep slopes and help reduce erosion throughout the park.

Sugar Maple:

• Found primarily in Harriman's cooler valleys and mesic forests where soils are deeper and more nutrient-rich.
• Identified by opposite branching, five-lobed leaves, and brilliant yellow-orange fall foliage.
• One of the most shade-tolerant hardwood species in eastern North America, allowing seedlings to establish beneath existing forest canopies before eventually replacing older trees (Burns & Honkala, 1990).
• Calcium-rich leaf litter decomposes rapidly, enriching soils and supporting diverse understory vegetation and microbial communities (Likens, 2013).
• Contributes significantly to long-term forest succession and nutrient cycling within mature hardwood forests.

Red Maple:

• One of the most adaptable tree species found in Harriman, occurring in wetlands, stream corridors, uplands, and disturbed forests.
• Identified by opposite leaves, reddish twigs, and vibrant scarlet fall foliage.
• Frequently colonizes canopy gaps following storms or other disturbances, making it an important early successional species.
• Early spring flowers provide one of the first nectar and pollen sources available to native bees and other pollinating insects (Dirr, 2009).
• Its broad ecological tolerance allows it to connect many of Harriman's different forest communities.

Eastern Hemlock:

• Grows primarily in cool ravines, north-facing slopes, and stream corridors throughout Harriman.
• Dense evergreen canopy creates cool, shaded microclimates that regulate stream temperatures, reduce evaporation, and maintain habitat for salamanders, brook trout, and many shade-dependent plant species (Ellison et al., 2005).
• Considered a foundation species because its presence influences the structure and function of entire forest ecosystems.
• Provides important winter cover for birds and mammals when deciduous trees have lost their leaves.
• Currently threatened by the invasive hemlock woolly adelgid, which has caused extensive mortality throughout the northeastern United States (USDA Forest Service, 2023).

American Beech:

• Common throughout mature hardwood forests where it grows alongside oaks and maples.
• Easily recognized by smooth gray bark and long, pointed winter buds.
• Produces beechnuts that are an important food source for black bears, squirrels, foxes, chipmunks, and many bird species (Burns & Honkala, 1990).
• Mature trees often develop cavities that provide nesting and denning sites for owls, woodpeckers, raccoons, and other wildlife.
• Although many populations have been affected by beech bark disease, the species continues to be an important contributor to forest biodiversity (Houston, 1994).

Black Birch:

• Common on moist slopes and in forest openings created by natural disturbance.
• Best identified by the distinctive wintergreen scent released when a twig is scratched.
• Functions as an early successional species that rapidly colonizes canopy gaps following storms or tree fall.
• Helps stabilize soils during forest recovery while providing browse for deer and seeds for numerous songbird species.
• Historically valued as a source of natural wintergreen oil because of its high methyl salicylate content.

Mountain Laurel:

• New York's official state shrub and one of the most recognizable understory plants in Harriman.
• Forms dense evergreen thickets beneath oak forests on acidic, rocky soils.
• Showy spring flowers support a variety of native bees and other pollinating insects (Dirr, 2009).
• Dense foliage provides valuable shelter and nesting habitat for many birds and small mammals.
• Thick stands can reduce tree seedling establishment by limiting light availability, influencing forest regeneration patterns.
• All parts of the plant contain toxic compounds and should not be consumed.

Flowering Dogwood:

• Small understory tree commonly found along woodland edges and beneath partially open forest canopies.
• Easily recognized by its white spring bracts and bright red fruits produced in late summer.
• Supports biodiversity throughout the growing season by providing nectar for pollinators and fruits for more than 35 bird species as well as numerous mammals (Dirr, 2009).
• Adds structural diversity to Harriman's forest understory and increases habitat complexity.
• Populations have declined across much of the eastern United States because of dogwood anthracnose, making healthy individuals increasingly valuable within protected forests (USDA Forest Service, 2018).

Black Gum:

• Found in wetlands, stream corridors, and rocky uplands throughout Harriman, demonstrating remarkable adaptability (Burns & Honkala, 1990).
• Identified by glossy oval leaves, horizontal branching, dark blocky bark, and brilliant scarlet fall foliage.
• Produces blue-black fruits that provide an important food source for migratory birds, wild turkey, foxes, and black bears (Dirr, 2009).
• Flowers support native pollinators, while extensive roots help stabilize soils near wetlands and streams.
• Its ability to thrive in both wet and dry habitats contributes to the resilience of Harriman's forest ecosystems.

Witch Hazel:

• Native understory shrub or small tree commonly found in deciduous forests and along woodland edges throughout Harriman (Dirr, 2009).
• Easily recognized by its yellow, ribbon-like flowers that bloom in late fall after most other plants have finished flowering.
• Provides an important late-season nectar source for native pollinators when few other woody plants are in bloom (Burns & Honkala, 1990).
• Dense growth offers cover for birds and small mammals and adds structural diversity to the forest understory.
• Historically valued for its medicinal properties and remains an important native species in northeastern forests.

Wrap up:

• Harriman's forests are composed of species adapted to a wide variety of environmental conditions, from dry ridge tops to cool stream valleys.
• Each species contributes differently to ecosystem function through food production, habitat creation, nutrient cycling, carbon storage, soil stabilization, and forest succession.
• Together, these native trees and shrubs support the exceptional biodiversity that makes Harriman State Park one of New York's most ecologically significant protected landscapes (Ellison et al., 2005; NYNHP, 2021).
• Understanding how to identify these species also provides insight into broader conservation challenges, including invasive pests, forest diseases, and climate-driven changes to northeastern forests.

References:

Burns, R. M., & Honkala, B. H. (Eds.). (1990). Silvics of North America: Volume 1. Conifers; Volume 2. Hardwoods(Agriculture Handbook 654). U.S. Department of Agriculture, Forest Service. 

Dirr, M. A. (2009). Manual of woody landscape plants: Their identification, ornamental characteristics, culture, propagation and uses (6th ed.). Stipes Publishing.

Ellison, A. M., Bank, M. S., Clinton, B. D., Colburn, E. A., Elliott, K., Ford, C. R., Foster, D. R., Kloeppel, B. D., Knoepp, J. D., Lovett, G. M., Mohan, J. E., Orwig, D. A., Rodenhouse, N. L., Sobczak, W. V., Stinson, K. A., Stone, J. K., Swan, C. M., Thompson, J., Von Holle, B., & Webster, J. R. (2005). Loss of foundation species: Consequences for the structure and dynamics of forested ecosystems. Frontiers in Ecology and the Environment, 3(9), 479–486. https://doi.org/10.1890/1540-9295(2005)003[0479:LOFSCF]2.0.CO;2

Houston, D. R. (1994). Major new tree disease epidemics: Beech bark disease. Annual Review of Phytopathology, 32, 75–87. https://doi.org/10.1146/annurev.py.32.090194.000451

Iverson, L. R., Prasad, A. M., Matthews, S. N., & Peters, M. P. (2008). Estimating potential habitat for 134 eastern U.S. tree species under six climate scenarios. Forest Ecology and Management, 254(3), 390–406. https://doi.org/10.1016/j.foreco.2007.07.023

Likens, G. E. (2013). Biogeochemistry of a forested ecosystem (3rd ed.). Springer.

New York Natural Heritage Program. (2021). Ecological communities of New York State (2nd ed.). New York Natural Heritage Program, New York State Department of Environmental Conservation.

New York State Office of Parks, Recreation and Historic Preservation. (n.d.). Harriman State Park. New York State Parks. https://parks.ny.gov/parks/harriman

U.S. Department of Agriculture, Forest Service. (2018). Dogwood anthracnose. U.S. Department of Agriculture Forest Service.

U.S. Department of Agriculture, Forest Service. (2023). Hemlock woolly adelgid. U.S. Department of Agriculture Forest Service.

Virginia Tech Department of Forest Resources and Environmental Conservation. (n.d.). Dendrology factsheets. Virginia Tech. https://dendro.cnre.vt.edu/dendrology/factsheets.cfm