* 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:

Hemlock - Hardwood Swamp (CEGL006226)

NatureServe Ecological Systems:

North-Central Appalachian Acidic Swamp (CES202.604)

NatureServe Group Level:

None

Origin of Concept

Fike, J. 1999. Terrestrial and palustrine plant communities of Pennsylvania. Pennsylvania Natural Diversity Inventory. Pennsylvania Department of Conservation and Recreation, Bureau of Forestry, Harrisburg, PA. 86 pp.

Pennsylvania Community Code*

UB : Hemlock – Mixed Hardwood Palustrine Forest

*(DCNR 1999, Stone 2006)

Similar Ecological Communities

If the conifer component is less than 25% of the canopy, the community is classified as one of several broadleaf palustrine woodland community types. Hemlock – Mixed Hardwood Palustrine Woodlands differ from Hemlock – Mixed Hardwood Palustrine Forests in that Hemlock – Mixed Hardwood Palustrine Woodlands have a more open canopy (< 60% canopy cover) and typically a denser shrub layer as well as seedlings and sapling of tree species.

Fike Crosswalk

Hemlock – Mixed Hardwood Palustrine Woodland

Conservation Value

This community can host a number of rare plant species including soft-leaved sedge (Carex disperma), log fern (Dryopteris celsa), Clinton's wood fern (Dryopteris clintoniana), glade spurge (Euphorbia purpurea), creeping snowberry (Gaultheria hispidula), lesser rattlesnake-plantain (Goodyera repens), kidney-leaved twayblade (Listera smallii), bristly black currant (Ribes lacustre), and swamp red currant (Ribes triste).

This community also serves as a buffer for sediment and pollution runoff from adjacent developed lands by slowing the flow of surficial water causing sediment to settle within waterways associated with this wetland community. Hemlock – Mixed Hardwood Palustrine Woodlands provide habitat cover for ruffed grouse (Bonasa umbellus), turkey (Meleagris gallopavo), and snowshoe hare (Lepus americanus). This community also serves as a buffer for sediment and pollution runoff from adjacent developed lands into streams by slowing the flow of surficial water causing sediment to settle within this wetland.

Threats

Hemlock – Mixed Hardwood Palustrine Woodlands are threatened by habitat alteration, deposition (sedimentation, agricultural runoff), and alterations to the hydrological regime (flooding due to beaver dams, lowering of water tables). Clearing and development of adjacent land can lead to accumulation of agricultural run-off and pollution, sedimentation, and insolation/thermal pollution. Eastern hemlock communities are threatened by hemlock woolly adelgid (Adelgis tsugae) infestations. A. tsugae is an exotic pest insect that feeds on the twigs of the eastern hemlocks causing defoliation, bud mortality, and, eventually, tree mortality within as little as four years (Young et al. 1995). As tree mortality occurs, light availability increases due to the widening of canopy gaps and provides opportunities for the colonization of invasive plant species within the understory (Orwig and Foster 1998).

Management

A natural buffer around the wetland should be maintained in order to minimize nutrient runoff, pollution, and sedimentation. The potential for soil erosion based on soil texture, condition of the adjacent vegetation (mature forests vs. clearcuts) and the topography of the surrounding area (i.e., degree of slope) should be considered when establishing buffers instead of relying on a pre-established distance for buffer width. The buffer size should be increased if soils are erodible, adjacent vegetation has been logged, and the topography is steep as such factors could contribute to increased sedimentation and nutrient pollution. Direct impacts should be avoided (e.g., roads, trails, filling of wetlands) and low-impact alternatives (e.g., elevated footpaths, boardwalks, bridges) should be utilized in situations where accessing the wetland cannot be avoided. Care should also be taken to control and prevent the spread of invasive species within the wetland. Alterations to groundwater sources should be minimized. This is a successional type therefore acreage and occurrences will fluctuate with time depending on the level and frequency of disturbance in a given watershed or region.

Range Map

Pennsylvania Range

Great Lakes Region, Glaciated NE, Glaciated NW, Pittsburgh Plateau, Pocono Plateau, Ridge and Valley, Unglaciated Allegheny Plateau.

Global Distribution

Unknown

Cowardin, L.M., V. Carter, F.C. Golet, and E.T. La Roe. 1979. Classification of wetlands and deepwater habitats of the United States. U.S. Fish and Wildlife Service. Washington, D.C. 131 pp.

Edinger, Gregory J., D.J. Evans, Shane Gebauer, Timothy G. Howard, David M. Hunt, and Adele M. Olivero. 2002. Ecological Communities of New York State. Second Edition. A revised and expanded edition of Carol Reschke's Ecological Communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Albany, NY. 136 pp.

Fike, J. 1999. Terrestrial and palustrine plant communities of Pennsylvania. Pennsylvania Natural Diversity Inventory. Harrisburg, PA. 79 pp.

NatureServe. 2009. NatureServe Central Databases. Arlington, Virginia. USA

Orwig, D. A., and D. R. Foster. 1998. Forest response to the introduced hemlock woolly adelgid in southern New England, USA. Journal of the Torrey Botanical Society 125: 60:73.

Pennsylvania Department of Conservation and Natural Resources (DCNR). 1999. Inventory Manual of Procedure. For the Fourth State Forest Management Plan. Pennsylvania Bureau of Forestry, Division of Forest Advisory Service.  Harrisburg, PA. 51 ppg.

Stone, B., D. Gustafson, and B. Jones. 2006 (revised). Manual of Procedure for State Game Land Cover Typing.  Commonwealth of Pennsylvania Game Commission, Bureau of Wildlife Habitat Management, Forest Inventory and Analysis Section, Forestry Division.  Harrisburg, PA. 79 ppg.

Young, R. F., K. S. Shields, and G. P. Berlyn. 1995. Hemlock woolly adelgid (Homoptera, Adelgidae)-stylet bundle insertion and feeding sites. Annals of Entomological Society of America 88: 827:835.