Ecology and Physical Setting
Hemlock-Northern Hardwood Forests are mixed forests of hemlock, pines, and hardwoods that are not nutrient-demanding. The moist soils are primarily till-derived, but can also be shallow-to-bedrock, or sandy or gravelly. These forests are often found in isolated patches, but they can also sprawl across hills and valleys, covering extensive areas.
Because of its shade tolerance, hemlock can survive under the hardwood canopy for long periods. In contrast, yellow birch, a common component of this community, is less shade tolerant. These two species do, however, share something in common: seeds of both need exposed mineral soil or mossy logs to germinate. As a result, they are often found growing together, especially in mature forests where there is abundant downed wood.
Vegetation
Eastern hemlock shares the canopy with yellow birch, sugar maple, and/or beech. Hemlocks comprise 25 to 75 percent of the canopy. Other species may include red maple, white pine, paper birch, and red spruce. The canopy components vary with climate and soils, but these forests are always northern in character. Red oak can be present, but other more southern species are lacking. The herb composition has some similarities with that of acidic Northern Hardwood Forests.
Wildlife Habitat
Hemlock-Northern Hardwood Forests occur as large patches and as matrix forests and provide some of the most widespread mixed-forest habitat in Vermont. Breeding bird species include blue-headed vireo, black-throated green warbler, and Blackburnian warbler. Black-throated blue warblers, broad-winged hawks, barred owls, and northern goshawks are associated with mature forests and interior forests. Fishers have home ranges of 10 square miles or more and prefer conifer or mixed forests. They travel regular circuits through the forest in search of prey, including porcupines, red squirrels, and northern flying squirrels—all common mammals in Hemlock-Northern Hardwood Forests. Wood frogs and spotted salamanders may be common on the forest floor around Vernal Pools.
Successional Trends
Successional trends are very similar to those in Northern Hardwood Forests. Mature examples are dominated by hemlock, beech, and yellow birch. Natural disturbances that create tip-ups and downed wood are important for maintaining hemlock. Early-successional species include aspen and paper birch.
Variants
- Hemlock-White Pine-Northern Hardwood Forest: White pine is an important component of the canopy and is persistent over time. These forests occur on coarse outwash soils.
- Hemlock-Yellow Birch Forest is found where there are abundant sites for yellow birch to germinate. Sugar maple and beech are uncommon.
Related Communities
- Dry Hemlock-Oak Forest has a similar abundance of hemlock, but is characterized by species that are more common in southern New England, such as white oak, black oak, chestnut oak, shagbark hickory, bitternut hickory, and black birch.
- Northern Hardwood Forest: The more nutrient-poor variants of this community are perhaps the most similar to Hemlock-Northern Hardwood Forest. Hemlock comprises less than 25 percent of the canopy.
- Hemlock Forest: Hemlock is dominant, comprising over 75 percent of the canopy.
Conservation Status and Management Considerations
There are no known large old forest examples of this community in Vermont, though there may be a few in Massachusetts. Silvicultural practices should consider the long-term ecological trends of the site. Leaving large downed logs is important for ensuring long-term persistence of hemlock and yellow birch.
Distribution/Abundance
This is a common community at elevations below 1,800 feet in Vermont in all biophysical regions except the Northeastern Highlands, where it is uncommon. It is common throughout the northeast.
Characteristic Plants
Trees
Abundant Species
Eastern hemlock – Tsuga canadensis
American beech – Fagus grandifolia
Yellow birch – Betula alleghaniensis
Occasional to Locally Abundant Species
Sugar maple – Acer saccharum
Red maple – Acer rubrum
Paper birch – Betula papyrifera
White pine – Pinus strobus
Red oak – Quercus rubra
Shrubs
Occasional to Locally Abundant Species
Striped maple – Acer pensylvanicum
Hobblebush – Viburnum lantanoides
Herbs
Occasional to Locally Abundant Species
Painted trillium – Trillium undulatum
Partridgeberry – Mitchella repens
Appalachian polypody – Polypodium appalachianum
Intermediate wood fern – Dryopteris intermedia
Indian pipes – Monotropa uniflora
Canada mayflower – Maianthemum canadense
Ground cedar – Diphasiastrum digitatum
Wintergreen – Gaultheria procumbens
Pink lady’s slipper – Cypripedium acaule
Sarsaparilla – Aralia nudicaulis
Staghorn clubmoss – Lycopodium clavatum
Rare and Uncommon Plants
Pinedrops – Pterospora andromedea
Associated Animals
Spotted salamander – Ambystoma maculatum
Wood frog – Lithobates sylvaticus
Smoky shrew – Sorex fumeus
Fisher – Pekania pennanti
Bobcat – Lynx rufus
Porcupine – Erethizon dorsatum
Northern flying squirrel – Glaucomys sabrinus
Red squirrel – Tamiasciurus hudsonicus
Hermit thrush – Catharus guttatus
Ruffed grouse – Bonasa umbellus
Blackburnian warbler – Setophaga fusca
Blue-headed vireo – Vireo solitarius
Red-eyed vireo – Vireo olivaceus
Black-throated green warbler – Setophaga virens
Black-throated blue warbler – Setophaga caerulescens
Hairy woodpecker – Picoides villosus
Pileated woodpecker – Dryocopus pileatus
Broad-winged hawk – Buteo platypterus
Barred owl – Strix varia
Rare and Uncommon Animals
Northern goshawk – Accipiter gentilis
Northern long-eared bat – Myotis septentrionalis
Places to Visit
Atherton Meadows Wildlife Management Area, Whitingham, Vermont Fish and Wildlife Department
Mount Mansfield State Forest, Stowe and Underhill, Vermont Department of Forests, Parks, and Recreation