Northern Hardwood Forest

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System: Terrestrial
Subsystem: Forest
PA Ecological Group(s): Appalachian-Northeast Mesic Forest

Global Rank:G4G5 rank interpretation
State Rank: S4

General Description

This community type is characterized by a mix of hardwood species including sugar maple (Acer saccharum), American beech (Fagus grandifolia), red maple (Acer rubrum), sweet birch (Betula lenta; primarily in northern PA), yellow birch (B. alleghaniensis), paper birch (B. papyrifera; primarily in southern PA), black cherry (Prunus serotina; less than 40% cover), and northern red oak (Quercus rubra). White ash (Fraxinus americana) and basswood (Tilia americana) may be present at richer sites but are often a minor component of the canopy. Oaks can be quite common depending on the topographic position. For example, in the North Central Appalachians and Northern Allegheny Plateau, oaks are common in Northern Hardwood Forests on mid-to-upper slopes where the community transitions to an oak-dominated, dry-mesic hardwood community type. Canopy cover is typically 50-95% . This community may support eastern hemlock (Tsuga canadensis) or white pine (Pinus strobus) in the canopy and subcanopy, but the relative cover of conifers is less than 25%. Common shrubs include striped maple (Acer pensylvanicum), Allegheny blackberry (Rubus allegheniensis; limited to canopy gaps), mountain holly (Ilex montana), elderberry (Sambucus canadensis), witch-hazel (Hamamelis virginiana), shadbush (Amelanchier arborea), ironwood (Carpinus caroliniana), hop-hornbeam (Ostrya virginiana), and gooseberry (Ribes cynosbati). The groundcover may range from species-rich to species-poor, depending on soil type and topography. Drier, more acid soils typically are species-poor, while mesic, higher pH soils typically are richer in herbaceous species. Common herbaceous species include intermediate wood fern (Dryopteris intermedia), Christmas fern (Polystichum acrostichoides), hay-scented fern (Dennstaedtia punctilobula), New York fern (Thelypteris noveboracensis), wood aster (Oclemena acuminata), violets (Viola blanda, V. rotundifolia, V. canadensis are ubiquitous), Indian cucumber-root (Medeola virginiana), wild-oats (Uvularia sessilifolia), shorthusk (Brachyelytrum spp.), Canada mayflower (Maianthemum canadense), Pennsylvania sedge (Carex pennsylvanica), a sedge (C. communis), and common wood-sorrel (Oxalis acetosella). Often, intermediate and Christmas ferns dominate the herb layer, but hay-scented fern is also (frequently) a dominant species. Northern hardwood forests on richer sites may include Jack-in-the-pulpit (Arisaema triphyllum), wake-robin (Trillium erectum), two-leaved toothwort (Cardamine diphylla), cut-leaved toothwort (C. concatenata), Appalachian sedge (Carex appalachica), and spring beauty (Claytonia virginiana). Nettle (Laportea canadensis) and jewelweed (Impatiens sp.) may be common, especially near seeps or drainages. Mesic sites may also support substantial bryophyte cover. Sites with a higher pH (often limestone bedrock influence) support a greater diversity of herbaceous species, including great spurred violet (Viola selkirkii), American ginseng (Panax quinquefolius), ramps (Allium tricoccum), blue cohosh (Caulophyllum thalictroides), and Allegheny foamflower (Tiarella cordifolia). In drier or more acidic sites, partridge-berry (Mitchella repens), teaberry (Gaultheria procumbens), and clubmosses (Lycopodium sp.) can be common.

Rank Justification

The Northern Hardwood Forest is a widespread matrix forest on moderately acidic, moderate to well-drained soils in the Allegheny Plateau of Pennsylvania and New York, the adjacent Lake Ontario and Lake Erie plains and in Lower New England to northern New Jersey.

 

The four subtypes/variations are tracked by the PA Natural Heritage Program separately; their S Ranks are based on the range and number of occurrences, condition of occurrences, and threats.

Identification

  • Plant species richness can vary substantially across the range of this community type in Pennsylvania and is associated with soils and topography
  • Total tree canopy cover is between 50-95%
  • Black cherry accounts for less than 40% relative cover in the canopy/subcanopy
  • A community type that can be highly variable; often an intermediate between richer hardwood-dominated (Sugar maple - Basswood) and acidic/less rich mixed hardwood conifer (Hemlock (white pine) - Northern Hardwood Forest) communities

* limited to sites with higher soil calcium
Vascular plant nomenclature follows Rhoads and Block (2007). Bryophyte nomenclature follows Crum and Anderson (1981).

International Vegetation Classification Associations:

USNVC Crosswalk:

None

Representative Community Types:

Transitional Northern Hardwood Forest (CEGL006632)
Beech – Tuliptree – Sugar Maple Forest (CEGL006296)
Transitional Northern Sugar Maple – Ash Rich Mesic Forest (CEGL006637)
Central Appalachian Northern Hardwood Forest (Yellow Birch – Northern Red Oak Type) (CEGL008052)

NatureServe Ecological Systems:

None

NatureServe Group Level:

Appalachian-Northeast Mesic Forest (G742)

Origin of Concept

Faber-Langedoen, D., Sneddon, L. Fleming, G., and Gawler, S. C. 2018. Transitional Northern Sugar Maple - Ash Rich Mesic Forest (CEGL006637). NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. (Accessed: February 11, 2022).

Fike, J. 1999. Terrestrial and palustrine plant communities of Pennsylvania. Pennsylvania Natural Diversity Inventory. Harrisburg, PA. 86 pp.

Fike, J., Sneddon, L. A., Largay, E., and Gawler, S. C. 2006. Beech - Tuliptree - Sugar Maple Forest (CEGL006296). NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. (Accessed: February 11, 2022).

Fleming, G. P. 2018. Central Appalachian Northern Hardwood Forest (Yellow Birch - Northern Red Oak Type) (CEGL008502). NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. (Accessed: February 11, 2022).

Gawler, S. C. and Faber-Langendoen, D. 2015. Transitional Northern Hardwood Forest (CEGL006632). NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. (Accessed: February 11, 2022).

Pennsylvania Community Code*

BB : Northern Hardwood Forest

*(DCNR 1999, Stone 2006)

Similar Ecological Communities

Because of the species diversity of the overstory, this type can be very similar to a number of Pennsylvania community types. Often mapped as large stands, Northern Hardwood Forests may demonstrate significant microsite variation in canopy dominance. These large mapping units could include pockets of dense hemlock, black cherry, white ash, and basswood, which can make classification difficult. The Pennsylvania Bureau of Forestry divides the Northern Hardwood Forest into two types based on the amount of black cherry in the overstory. The Black Cherry – Northern Hardwood Forest type has more than 40% black cherry cover in canopy, and typically less sugar maple, ash, and yellow birch. In northern Pennsylvania, Red Oak – Mixed Hardwood Forests may also be similar in understory composition but have a larger (greater cover or basal area) red oak component in the canopy/subcanopy than Northern Hardwood Forests. In southern Pennsylvania, particularly in the Central Appalachians and Western Allegheny Plateau, the Northern Hardwood Forest may less resemble Red Oak – Mixed Hardwood Forests. Additionally, in southern Pennsylvania, the Northern Hardwood Forest may be restricted to north-facing slopes, cool ravines, and/or mesic soils, and may be associated with Hemlock (white pine) – Northern Hardwood Forests, or rarely the Rich Hemlock – Mesic Hardwood Forest.

 

The Northern Hardwood Forest can also be similar to the Sugar Maple – Basswood Forest. The Sugar Maple – Basswood Forest is more consistently rich, and white ash and basswood have greater relative cover in the canopy.

Fike Crosswalk

Northern Hardwood Forest

Conservation Value

The Northern Hardwood Forest community type is common in Pennsylvania and is found in nearly all of the state’s ecoregions. Although this community type supports a number of state-listed species, the community itself does not require special conservation action. A number of state-listed plant species have been documented in Northern Hardwood Forests, including great-spurred violet (Viola selkirkii; Hnatkovich, 2014). Breeding bird species that prefer forest interior conditions in the Northern Hardwood Forest include the veery (Catharus fuscescens), ovenbird (Seiurus aurocapilla), red-eyed vireo (Vireo olivaceus), and scarlet tanager* (Piranga olivacea; Sargent et al., 2017). * SGCN species

Threats

While there are no short-term conservation risks for the Northern Hardwood Forest community at this time, it could experience significant changes in the composition or distribution in a changing climate. Some authors have suggested that species that are currently dominant in our Northern Hardwood Forests, such as sugar maple, eastern hemlock, red maple, or black cherry, could become less common in both high and low emissions scenarios (Iverson et al., 2008; Peters et al., 2020). Forest pests/pathogens could significantly impact tree species in this community type, including emerald ash borer (EAB; Agrilus planipennis), hemlock wooly adelgid (HWA; Adelges tsugae), and beech bark disease. Invasive plant species such as garlic mustard (Alliaria petiolata) and Japanese barberry (Berberis thunbergii) are also a threat to Northern Hardwood Forests.

 

Throughout much of its range, the Northern Hardwood Forest has experienced forest fragmentation from roads, shallow gas development, and habitat conversion. Furthermore, the core range of the Northern Hardwood Forests overlaps with the shale gas region in Pennsylvania and New York. Development of the shale gas region, specifically the Marcellus Shale, may result in significant and continued fragmentation throughout the range in Pennsylvania.

Management

Northern Hardwood Forests can be sustainably managed. However, forest conditions may require a specific plan to achieve management goals. Private landowners can consult with service foresters at the Pennsylvania Bureau of Forestry for more information on sustainable forest management practices that are best suited for their property. Invasive species treatment is encouraged. Management of white-tailed deer could improve forest regeneration in forests experiencing high herbivory pressure.

Research Needs

Monitoring of Northern Hardwood Forests in Pennsylvania could benefit from adaptive management efforts in the context of climate change. Shifts in species dominance could impact the distribution of this community type as it is currently described (Bauer et al., 2016; Shortle et al., 2015). Providing periodic updates to community mapping throughout Pennsylvania may be an effective monitoring tool in the future. Maintaining up-to-date maps of plant communities is both important for rare species as well as more common species for ecological modeling efforts.  

Trends

About 20% of all mapped forests on State Forests and State Game Lands (combined) are classified as Northern Hardwood Forests (as of 2014). There is some evidence of widespread distribution of the Northern Hardwood Forest prior to European settlement. Pre-settlement vegetation has been reconstructed in the High Allegheny Plateau (Black et al., 2006; Thomas-Van Gundy et al., 2015), and Western Allegheny Plateau (Whitney, 1982; Whitney & DeCant, 2003) where northern hardwoods were dominant (Using the History of Pennsylvania Wildfire to Inform Landscape Level Prescribed Burn Planning, 2015). However, the historical distribution and abundance of Northern Hardwood Forests relative to oak dominated forests is not clear.

Range Map

range map

Pennsylvania Range

The Northern Hardwood Forest is found in the following USEPA Level III (IV) Ecoregions: Erie Drift Plain (61), Northern Central Appalachians (62), Ridge and Valley (67), Central Appalachians (69), Western Allegheny Plateau (70) and Eastern Great Lakes Lowlands (83).

Global Distribution

Massachusetts, New Jersey, New York, Pennsylvania; Ontario

Black, B. A., Ruffner, C. M., & Abrams, M. D. (2006). Native American influences on the forest composition of the Allegheny Plateau, northwest Pennsylvania. Canadian Journal of Forest Research, 36(5), 1266-1275.

Hnatkovich, A. (2014). Habitat assessment and conservation planning for Viola selkirkii (great-spurred violet) in north central Pennsylvania (Agreement #12463; p. 50). Western Pennsylvania Conservancy, Pennsylvania Natural Heritage Program.

Iverson, L. R., Prasad, A. M., Matthews, S. N., & Peters, M. (2008). Estimating potential habitat for 134 eastern US tree species under six climate scenarios. Forest Ecology and Management, 254(3), 390-406.

Peters, M. P., Prasad, A. M., Matthews, S. N., & Iverson, L. R. (2020). Climate change tree atlas, Version 4. U.S. Forest Service, Northern Research Station and Northern Institute of Applied Climate Science, Delaware, OH. https://www.fs.fed.us/nrs/atlas/tree/

Sargent, S., Yeany III, D., Michel, N., & Zimmerman, E. (2017). Forest Interior Bird Habitat Relationships in the Pennsylvania Wilds, Final Report for WRCP-14507. Audubon Pennsylvania, National Audubon Society.

Thomas-Van Gundy, M. A., Nowacki, G. J., & Cogbill, C. V. (2015). Mapping pyrophilic percentages across the northeastern United States using witness trees, with focus on four national forests. Gen. Tech. Rep. NRS-145. Newtown Square, PA: US Department of Agriculture, Forest Service, Northern Research Station. 26 p., 145, 1-26.

Using the history of Pennsylvania wildfire to inform landscape level prescribed burn planning (Final Report to the Pennsylvania Department of Conservation and Natural Resources, Wild Resource Conservation Program). (2015). Pennsylvania Natural Heritage Program.

Whitney, G. G. (1982). Vegetation-site relationships in the presettlement forests of northeastern Ohio. Botanical Gazette, 143(2), 225-237.

Whitney, G. G., & DeCant, J. P. (2003). Physical and historical determinants of the pre-and post-settlement forests of northwestern Pennsylvania. Canadian Journal of Forest Research, 33(9), 1683-1697.

Cite as:
Braund, J., E. Zimmerman, A. Hnatkovich, and J. McPherson. 2022. Pennsylvania Natural Heritage Program. Northern Hardwood Forest Factsheet. Available from: https://www.naturalheritage.state.pa.us/Community.aspx?=16058 Date Accessed: May 19, 2024

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