Rich Northern Hardwood Forest

Ecology and Physical Setting

Rich Northern Hardwood Forests are quintessentially Vermont. Sugar maple is abundant, making these forests vital to three of Vermont’s economic staples: maple sugar production, forestry, and tourism. Rich Northern Hardwood Forests are places where colluvial processes (downslope movement) or mineral-rich bedrock, or some combination of the two, provide plants with a steady supply of nutrients. 

Colluvial processes prevail on lower slopes and benches and also in coves and gullies. Here organic matter and plant nutrients accumulate over time, forming a compost-like soil. If the bedrock or till on such a slope is enriched with calcium and other key plant nutrients, these nutrients will be washed from upper to lower slopes, giving the plants below the greatest advantage. Productivity is high on the lower slopes, as is the overall diversity of plant species. The upper slopes or the convex knobs on such a hill, where nutrients are leached from the soils, will have communities—such as Northern Hardwood Forest, Hemlock Forest, Red Oak-Northern Hardwood Forest, or Dry Oak-Hickory-Hophornbeam Forest—with lower species diversity and lower productivity. 

Rich Northern Hardwood Forests can also be found on rolling terrain where calcium-rich bedrock is found close to the surface. Although soils on these sites can be shallow and droughty, the bedrock nevertheless provides ample plant nutrients. Pockets of rich soil are commonly mixed with the small outcrops of calcareous rock. These sites can be quite productive and diverse, with many plants that indicate mineral enrichment. 

Overall, the soils in Rich Northern Hardwood Forests range from well drained to somewhat poorly drained. Sometimes there is a dense hardpan at about 18-24 inches from the surface. This restricting layer can be a factor in keeping moisture and nutrients near the surface, where they are readily available to plants. Where soils are moist, productivity is higher, trees produce higher quality wood, and herbaceous plants are more abundant. 

Vegetation

Rich Northern Hardwood Forests are high productivity forests: trees grow quickly, and they grow tall and straight. Sugar maple is dominant in the canopy, but basswood and white ash are common as well, and butternuts are scattered. The shrub layer varies from being almost absent in dense shade to well developed in sunny openings. Herbs are often abundant on the forest floor, forming a continuous carpet of lush vegetation in midsummer. Where moisture is plentiful, ferns such as ostrich fern, narrow leaf glade fern, and silvery glade fern form dense fern glades. Most of the herbs are long-lived perennials. Many of them are spring ephemerals that flower and fruit early in spring before trees leaf out, when sunlight is plentiful. By mid-summer some of these plants, like Dutchman’s breeches, have lost all their foliage and are completely invisible above ground. Other plants, like wood nettle and maidenhair fern, persist throughout the summer, displaying large canopies of leaves to gather the filtered light on the forest floor. 

The overall diversity of species is high in Rich Northern Hardwood Forests, as is the sheer abundance of biomass on the forest floor. A study of forests in Vermont and New York showed that in plots of uniform size (0.1 hectare, or about 1/4 acre), a representative Rich Northern Hardwood Forest in the Green Mountains had an average of 48 herb species, while other hardwood forest types in the Adirondacks had an average of 27 species. Other studies show similar results. 

Wildlife Habitat

Rich Northern Hardwood Forests provide very similar wildlife habitat as Northern Hardwood Forests and support many of the same species. Eastern red-backed salamanders thrive in the rich, moist soils. Spotted salamanders, wood frogs, and other vernal pool species may be present if there is a pool nearby. Breeding birds include hermit thrush, rose-breasted grosbeak, ovenbird, and scarlet tanager. The West Virginia white is a rare butterfly that feeds primarily on the nectar of toothwort, a plant of rich woods. This butterfly remains in the same forest patch that contains its host plant for its entire life. The species is now threatened by forest fragmentation and the spread of non-native invasive plants.

Successional Trends

Rich Northern Hardwood Forests that have been undisturbed for long periods of time will likely be dominated by sugar maple, white ash, and basswood. Forests where natural or human disturbances have created openings may be dominated by a combination of sugar maple, bigtooth aspen, white ash, striped maple, black cherry, white pine, yellow birch, and pin cherry. Which of these species dominate, and for how long, will depend on climate, history, seed sources, and site conditions. 

Variants

• Dry Rich Northern Hardwood Forest: This is a Rich Northern Hardwood Forest on well-drained, shallow-to-bedrock soils, primarily associated with the Waits River formation in the Northern Vermont Piedmont. Hophornbeam and white ash are typically common in the canopy. This variant is very similar to Dry Oak-Maple Limestone Forest. 

Related Communities

• Northern Hardwood Forest is the community most closely related to Rich Northern Hardwood Forest. The two differ in the availability of plant nutrients in the soils and in species diversity. Often these communities interfinger, with Rich Northern Hardwood Forest occurring in rich coves or benches, surrounded by Northern Hardwood Forest.
  
   
• Mesic Maple-Ash-Hickory-Oak Forest can be in similar settings as Rich Northern Hardwood Forest, but differs in having southern species such as hickories and oaks. 
  
   
• Dry Oak-Maple Limestone Forest is found in areas of shallow soils over limestone or dolostone in the Champlain Valley and other warm-climate areas, and has much in common with Rich Northern Hardwood Forest, but species composition reflects a warmer climate and southern affinities. 
  
   
• Northern Hardwood Seepage Forest can be highly enriched from groundwater, and can share many species with Rich Northern Hardwood Forest. It is distinguished by the presence of groundwater seepage and a predominance of wetland conditions.

Conservation Status and Management Considerations

Rich Northern Hardwood Forests are common in Vermont, though most examples are small. Exceptionally large examples occur in the eastern Taconic Mountains and are partially protected. Several examples elsewhere are protected as natural areas, and a number of sites are under timber management that considers the long-term ecological integrity of the natural community. 

The observations of foresters and ecologists indicate that this community type can recover well from selective harvest, if patch cuts are kept small and precautions are taken against the encroachment of invasive non-native plants, which thrive in the rich soils. Industrial-scale maple sugaring is a new and increasing use that can have long-term effects on these forests. Maintaining a diverse mix of tree species in addition to sugar maple is an important management strategy in any sugarbush. Clearing for agriculture probably has a long-term impact on these forests; the native flora may take a long time to return after a Rich Northern Hardwood Forest site is used for agriculture. In general, activities that alter the downslope movement of soil and nutrients, such as the building of roads across slopes, threaten the integrity of this community.

Rich Northern Hardwood Forests are being changed by the introduction of non-native insects and pathogens. Emerald ash borer will likely kill most of the large white ash in this community, and butternut canker has all but eliminated the butternuts. Finding a living butternut in this community—something that used to be a common occurrence—is today a rare treat. 

Distribution/Abundance

Rich Northern Hardwood Forests occur throughout Vermont at low to moderate elevations, from approximately 300 to 2,500 feet. They are most common where the bedrock is calcareous but are also present in areas of nutrient-enriched till or topographically induced enrichment. This community occurs throughout the northeastern United States and adjacent Canada but is less common in neighboring states. Vermont may have the largest examples of this natural community type in the northeast.

Characteristic Plants

Trees

Abundant Species 

Sugar maple – Acer saccharum

White ash – Fraxinus americana

Occasional to Locally Abundant Species

Basswood – Tilia americana 

Black birch – Betula lenta

Bitternut hickory – Carya cordiformis

Yellow birch – Betula alleghaniensis

American beech – Fagus grandifolia 

Black cherry – Prunus serotina

Butternut – Juglans cinerea

Hophornbeam – Ostrya virginiana

Shrubs

Abundant Species 

Striped maple – Acer pensylvanicum

Alternate-leaved dogwood – Cornus alternifolia

Occasional to Locally Abundant Species

Maple-leaved viburnum – Viburnum acerifolium

Red-berried elder – Sambucus racemosa 

Round-leaved dogwood – Cornus rugosa

Leatherwood – Dirca palustris

Herbs

Abundant Species 

Wood nettle – Laportea canadensis

Maidenhair fern – Adiantum pedatum

Blue cohosh – Caulophyllum thalictroides

Wild leeks – Allium tricoccum

Dutchman’s breeches – Dicentra cucullaria

Sharp-lobed hepatica – Anemone acutiloba

Canada violet – Viola canadensis

Pale touch-me-not – Impatiens pallida

Wild ginger – Asarum canadense

Bulblet fern – Cystopteris bulbifera

Christmas fern – Polystichum acrostichoides

White snakeroot – Ageratina altissima 

Occasional to Locally Abundant Species

Squirrel corn – Dicentra canadensis

Common toothwort – Cardamine diphylla

Early yellow violet – Viola rotundifolia

Silvery glade fern – Deparia acrostichoides

White baneberry – Actaea pachypoda

Plantain-leaved sedge – Carex plantaginea

Zigzag goldenrod – Solidago flexicaulis

Black snakeroot – Sanicula marilandica

Rattlesnake fern – Botrychium virginianum

Virginia waterleaf – Hydrophyllum virginianum

Herb Robert – Geranium robertianum

Goldie’s wood fern – Dryopteris goldiana

Sprengel’s sedge – Carex sprengelii 

Wood millet – Milium effusum

Invasive Non-native Plants 

Morrow’s honeysuckle – Lonicera morrowii

Tatarian honeysuckle – Lonicera tatarica

Japanese barberry – Berberis thunbergii

Common buckthorn – Rhamnus cathartica

Wall-lettuce – Mycelis muralis 

Rare and Uncommon Plants

American ginseng – Panax quinquefolius

Narrow leaf glade fern – Homalosorus pycnocarpos

Hitchcock’s sedge – Carex hitchcockiana

Summer sedge – Carex aestivalis

Hooker’s orchis – Platanthera hookeri

Goldenseal – Hydrastis canadensis

Broad beech fern – Phegopteris hexagonoptera

Male fern – Dryopteris filix-mas

Puttyroot – Aplectrum hyemale

Small roundleaf orchis – Platanthera orbiculata

Drooping bluegrass – Poa saltuensis ssp. saltuensis

Associated Animals

Eastern red-backed salamander – Plethodon cinereus 

Eastern Newt – Notophthalmus viridescens 

Eastern chipmunk – Tamias striatus 

Hermit thrush – Catharus guttatus 

Rose-breasted grosbeak – Pheucticus ludovicianus 

Ovenbird – Seiurus aurocapilla

Red-eyed vireo – Vireo olivaceus 

Black-and-white warbler – Mniotilta varia 

Black-throated blue warbler – Setophaga caerulescens 

Scarlet tanager – Piranga olivacea

Hairy woodpecker – Picoides villosus 

Rare and Uncommon Animals

West Virginia white – Pieris virginiensis

Northern long-eared bat – Myotis septentrionalis

Places to Visit

Mount Equinox, Manchester, Equinox Preservation Trust, The Nature Conservancy and Vermont Land Trust

Gifford Woods, Killington, Vermont Department of Forests, Parks, and Recreation (VDFPR)

Willoughby State Forest, Westmore and Sutton, VDFPR