Northern Hardwood Forests of the Adirondacks

Adirondack Northern Hardwood Forest: The rich tapestry of hardwoods that characterizes the northern hardwood forest is conveniently seen in the autumn, when the orange and yellows of birch and aspen contrast with the orange-reds of maples. Autumn colors from the Old Orchard Loop at Heaven Hill. (6 October 2018).

The northern hardwood forest is the most extensive woodland in the Adirondacks. It occupies the region's best soils and sites, growing on the more fertile soils that make up glacial till. The northern hardwood forest is generally found on the lower and warmer mountainsides – gentle slopes where soils are neither extremely dry nor extremely wet.

The most dominant life form in the northern hardwood forest are deciduous trees, which lose their leaves each fall and are almost completely dormant in the winter months. One of the most striking characteristics of the northern hardwood forest is the extravagant display of fall colors, which results from the loss of green pigment, chlorophyll, as the trees slow down their photosynthesis in the autumn and prepare to enter dormancy for the winter. With the chlorophyll gone, pigments which were hidden previously become visible, producing the vibrant reds of the Sugar Maple and the golden yellows of the American Beech.

Northern hardwood forests in the Adirondacks can be recognized from afar by the color and pattern of foliage.

• In spring, before leaf-out, the grey-brown pattern of unleafed branches contrasts with the somber dark green expanse of conifers both above and below the hardwoods.
• In summer, hardwood forests can be distinguished by areas of bright green foliage.
• In fall, the oranges, yellows, and reds of deciduous trees stand out against the dark greens of the conifers.

Trees of the Northern Hardwood Forest

Trees of the Adirondacks: Sugar Maple leaves turn red, yellow, or orange in autumn, contributing to the brilliant palette of colors seen in September and early October in the Adirondacks. Sugar Maple on the Heart Lake Trail (2 October 2018).

The two dominant tree species in the northern hardwood forest are Sugar Maple and American Beech, both of which can tolerate more shade than other hardwoods and thrive on deep, fertile, well-drained till. Also present in some areas is Yellow Birch, which requires somewhat more sun and does well on both till and outwash, and Eastern Hemlock.  The mix of trees on any given site varies with the elevation, soil, topography, and water table. 

The Sugar Maple – growing in abundance with Yellow Birch, Eastern Hemlock, American Beech, and Eastern White Pine – is an indicator species for the northern hardwood forest. On those areas most suited for hardwoods, Sugar Maple is the dominant species.  This tree can also be found  in mixed hardwood-conifer forests. Although the Sugar Maple grows in a wide variety of soils, it does best on deep, well-drained soils. It is rarely found in swamps, because it does not tolerate wet soils.

Sugar Maple is a food source for several wildlife species. White-tailed Deer, Moose, and Snowshoe Hares commonly browse on Sugar Maple trees. Red Squirrels feed on its seeds, buds, twigs, and leaves. Porcupines eat the bark and can girdle the upper stem.  A number of birds build nests in Sugar Maples, including American Redstarts, Evening Grosbeaks, Baltimore Orioles, and Northern Cardinals. For several species – including the Cerulean Warbler, Scarlet Tanager, Hairy Woodpecker, and Summer Tanager – the Sugar Maple is one of the preferred trees for foraging for insects.

Trees of the Adirondacks: The leaves of American Beech trees turn yellowish to reddish brown in the fall. American Beech at the Paul Smith's College VIC (13 October 2013).

American Beech is the other dominant species in northern hardwood forests of the Adirondacks.  It also occurs in mixed hardwoods with Sugar Maple, birch, and hemlock. American Beech trees do best in well-drained upland sites and are not found in wetlands.  American Beech trees contribute to the brilliant fall color of the Adirondacks, turning golden yellow or lustrous brown in late September and October, then pale brown in autumn. The leaves remain on the tree well into winter.

Beech nuts are an important source of food for wildlife, including Raccoons, White-tailed Deer, Porcupines, and foxes, as well as squirrels and chipmunks. Beechnuts are also consumed by Black Bears, who load up on calories for winter hibernation. The American Beech also provides food and nesting sites for a variety of birds. American Beech trees are used as a nest site by Cooper's Hawks and American Redstarts. American Beech trees provide nest cavities for cavity nesters, like the Wood Duck. Beechnuts are an important food source for Blue Jays, Red-headed Woodpeckers, White-breasted Nuthatches, and Red-bellied Woodpeckers.

Shrubs of the Northern Hardwood Forest

Shrubs of the Adirondacks: The Hobblebush, so named for its pendulous branches which form obstacles which easily trip (or hobble) walkers, is commonly found in Adirondack hardwood and mixed wood forests. Hobblebush on the Henry's Woods Loop Trail (23 May 2018). 

The understory of the northern hardwood forest includes several species of shrub:  

Hobblebush, which also occurs commonly in mixed wood forests, is a native deciduous shrub which abounds in rich, moist woods throughout the Adirondack Mountains. It produces flat-topped clusters of fragrant white flowers in the spring. The flowers are followed in September by red berries gradually changing to dark blue, and attractive bronze-red or purple foliage in the fall. This shrub grows to a height of three to six feet. Hobblebush serves a variety of wildlife. Browsers eat its twigs and leaves. Game birds, songbirds, and mammals eat the fruit.

Another common understory plant is Striped Maple, an indicator species of the Northern Hardwood forest. It is a deciduous understory tree or large shrub which flourishes in cool, moist woods in the Adirondack Mountains. Striped Maple leaves turn yellow in the fall. These plants can also be found in mixed wood forests. The Striped Maple is an important browse plant for wildlife. Its twigs are browsed by Snowshoe Hares. Red Squirrels and Eastern Chipmunks eat the seeds. Striped Maple is frequently eaten by North American Porcupines. The Striped Maple also provides browse for White-tailed Deer and Moose.  Striped Maple are also very useful to wildlife in that these understory plants help diversify the vertical profile of a forest, creating the dense layers in a woodland that are attractive to many wildlife species for nesting, feeding, and perching.

Wildflowers and Ferns of the Northern Hardwood Forest

Wildflowers of the Adirondacks: The Trout Lily, like other spring ephemerals, takes advantage of the full sun hitting the forest floor early in the growing season. Trout Lily on the Big Field Loop at Heaven Hill (14 May 2018).

The wildflowers and ferns that flourish in the deeply-shaded forest floor of a mature northern hardwood forest are those that are very tolerant of shade. The only sun-loving wildflowers which bloom in a mature hardwood forest are found on the edges of wide trails or in places where a blowdown or other disturbance has created a gap in the tree canopy.

Northern hardwood forests are home to a group of spring-blooming wildflowers known as spring ephemerals. These are perennial woodland plants that sprout from the ground in deciduous forests in early each spring, then quickly bloom and seed before the canopy trees overhead leaf out. Once the leaves of the deciduous trees above are fully-developed and the forest floor is deep in shade, the foliage of these plants wither away leaving just the roots, rhizomes, and bulbs underground.

Spring ephemerals that bloom in the Adirondack Mountains include Trout Lily, Dutchman's Breeches, Squirrel Corn, Carolina Spring Beauty, and Dwarf Ginseng. You can also find many of these plants in mixed wood forests, but almost always under deciduous trees. These little plants emerge, bloom, and die back very quickly, sometimes (depending on the weather) in a matter of a few days, so nature lovers seeking to find them need to carefully time their spring wildflower walks.

Wildflowers of the Adirondacks: Purple Trillium is a shade-tolerant wildflower which blooms in the northern hardwood forest. Purple Trillium at the Adirondack Wildlife Refuge (11 May 2018).

Other shade-tolerant wildflowers common in northern hardwood forests in our region include Purple Trillium, Indian Cucumber-root, Jack-in-the-Pulpit, Canada Mayflower, Starflower, and Wild Sarsaparilla. Most bloom in the spring, many in dappled sunlight before the leaves of the maples and beeches above have fully developed. Many of these plants may also be found in mixed wood forests, often in proximity to a group of deciduous trees.

Ferns – non-flowering, perennial plants that reproduce by spores – are an important component of the forest understory. Together with wildflowers, they form an intermediate layer between the understory and a litter layer of decomposing leaves and wood.

Ferns found in the northern hardwood forest include Northern Lady Fern, Bulbet Fern, Christmas Fern, Maidenhair Fern, Interrupted Fern, Hay-scented Fern, Intermediate Woodfern, and New York Fern. Two fern allies – Shining Clubmoss and Tree Clubmoss (or Ground Pine) – are also found in this habitat in abundance.

Wildlife of the Northern Hardwood Forest

Birds of the Adirondacks: Black-and-white Warblers prefer mature and second-growth deciduous and mixed deciduous-coniferous forests. Black-and-white Warbler in the woods near the Cemetery Road Wetlands (18 July 2018).

Birds that make their home in the northern hardwood forest of the Adirondack Mountains include year-round residents (primarily generalists like the Black-capped Chickadees, Common Ravens, and Downy Woodpeckers).

The list of birds that breed in northern hardwood forests also includes summer residents, such as Ovenbird, Wood Thrush, Red-eyed Vireo, Eastern Wood-Pewee, Black-and-white Warbler, Black-throated Blue Warbler, Veery, and Scarlet Tanager.

• Some summer residents who breed in the northern hardwood forest, such as the Ovenbird, favor mature forests.
• Other birds prefer successional forests – deciduous forests that are regenerating from natural or man-made disturbances. Examples include the Chestnut-sided Warbler (which breeds in early successional deciduous woods) and the Veery (which breeds in disturbed and successional northern hardwood forests).

Some of these summer migrants rely on the deciduous forest for both feeding and nesting sites. The Scarlet Tanager, for instance, prefers mature deciduous forest during breeding season and often nests in maple or beech. This bird commonly forages on three of the primary deciduous trees of the northern hardwood forest: Sugar Maple, American Beech, and Yellow Birch.

Mammals of the Adirondacks: Although the Gray Fox can be found in mixed forests and forest-farmland edges, it favors deciduous woodland. Gray Fox near Country Club Lane, Lake Placid (5 July 2015).

Characteristic mammals of the northern hardwood forest in the Adirondacks include the Eastern Chipmunk, Gray Squirrel (along the eastern and southern margins of the mountains), Southern Flying Squirrel, Gray Fox, Porcupine, Black Bear, Eastern Coyote, Striped Skunk, Fisher, Raccoon, Bobcat, and White-tailed Deer.

These species rely to varying degrees on deciduous trees as a vital food source. The Yellow Birch, for example, provides browse for White-tailed Deer. Moose, Eastern Cottontail, and Snowshoe Hare also use the plant for food. Red Squirrels cut and store the mature catkins of the birch and eat the seeds. American Beaver and North American Porcupine chew the bark.

Many of the mammal species who live in this habitat, like the Eastern Chipmunk, Gray Fox, and Fisher, can also be found in mixed wood forests. Others, like the White-tailed Deer, can also be found in farmlands and the brushy areas of successional fields.

Butterflies of the Adirondacks: Caterpillar hosts of the Canadian Tiger Swallowtail include the leaves of birch, aspen and black cherry. Canadian Tiger Swallowtail near Hulls Falls Road (9 June 2018).

Some species of butterflies and moths make use of the northern hardwood forest in the Adirondack Mountains.

• Butterflies that use deciduous trees as their caterpillar hosts include the Eastern Comma, Spicebush Swallowtail, and Canadian Tiger Swallowtail.
• The Spotted Tussock Moth is usually found in boreal forests containing its host plants: deciduous trees. This small, attractive moth is usually seen in the Adirondack Mountains in June.
• One of our silkmoths, the  Promethea Silkmoth, a large moth which may be seen in the Adirondack Mountains in upstate New York in late May and early June, also favors deciduous woodlands.
• The Luna Moth, a large nocturnal moth that may be seen in the Adirondacks in June, also lives in deciduous hardwood forests. 
• The Rosy Maple Moth can also be found in hardwood forests; its preferred host is the maple.

Amphibians of the Adirondacks: The Eastern Newt is known as a Red Eft during its terrestrial stage. Red Eft at the Paul Smith's College VIC (7 June 2012).

Amphibians and Reptiles of the Adirondack hardwood forest include the Eastern Newt, Spotted Salamander, Blue-spotted Salamander, Two-lined Salamander, Gray Treefrog, Wood Frog, American Toad, and Common Garter Snake. Some are generalists, like the Common Garter Snake, and are found in many terrestrial habitats.

The Eastern Newt only appears in this habitat during its terrestrial stage, when it is known as a Red Eft. These creatures begin life as eggs which hatch into aquatic larval newts, which then transform into brightly-colored Red Efts in their terrestrial stage. Red Efts spend several years on land. During the juvenile Red Eft stage, this amphibian is found on moist forest floors. Red Efts are typically found under leaf litter, brush piles, logs and stumps. They occur in forests of any type, but seem to prefer deciduous and mixed forests. Red Efts are mostly diurnal. Look for them in the leaf litter of the forest floor. The bright orange color warns predators of their toxic skin secretions. The eft later returns to water, transforming into aquatic adults.

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