* 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:

Allegheny Floodplain Alder Thicket (CEGL006251)

NatureServe Ecological Systems:

Central Appalachian River Floodplain (CES202.608)

NatureServe Group Level:

None

Origin of Concept

Pennsylvania Natural Heritage Program. 2004. Classification, Assessment and Protection of Non-Forested Floodplain Wetlands of the Susquehanna Drainage. Report to: The United States Environmental Protection Agency and the Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry, Ecological Services Section. US EPA Wetlands Protection State Development Grant no. CD-98337501.

Pennsylvania Community Code*

SA : Hawthorn – Mixed Species Shrub Wetland

*(DCNR 1999, Stone 2006)

Similar Ecological Communities

Acidic Mixed Shrub – Sphagnum Wetland and Alder – Dogwood Floodplain Thicket can both be dominated by alders (Alnus spp.) but Acidic Mixed Shrub – Sphagnum Wetland is typically found in upland depression settings, contains sphagnum moss (Sphagnum spp.), and is generally more acidic. Alder – Dogwood Floodplain Thickets typically occur along active stream channels, lack sphagnum moss, and are circumneutral.

Mixed Hardwood Floodplain Thicket and Alder – Dogwood Floodplain Thicket contain similar species and occur along riverine settings. The main difference is that Mixed Hardwood Floodplain Thicket is dominated by a combination of species such as sycamore (Platanus occidentalis), silver maple (Acer saccharinum), eastern cottonwood (Populus deltoides), river birch (Betula nigra), and black willow (Salix nigra), but may be co-dominated by alders and the Alder – Dogwood Floodplain Thicket is clearly dominated by alders and dogwoods (Cornus spp.).

Fike Crosswalk

Alder - dogwood riverine shrubland

Conservation Value

The community is an important part of the river floodplain ecosystem, which provides significant ecosystem services in addition to wildlife habitat, such as sediment control, filtering runoff, and cooling overland flow of water. Floodplain shrublands provide important habitat for many bird species of conservation concern such as alder flycatchers (Empidonax alnorum), willow flycatchers (Empidonax traillii), and wood-warbler species (Parulidae spp.).

Threats

Alteration to the frequency and duration of flood events and the development of river floodplains are the two greatest threats to this community statewide and can lead to habitat destruction and/or shifts in community function and dynamics. Non-native invasive plants may be equally devastating as native floodplain plants are displaced. Development of adjacent land can lead to an accumulation of agricultural run-off, pollution, and sedimentation. This community can be threatened by Japanese knotweed (Fallopia japonica), Japanese stiltgrass (Microstegium vimineum), multiflora rose (Rosa multiflora), Morrow’s honeysuckle (Lonicera morrowii), and gill-over-the-ground (Glechoma hederacea), which can displace native grass and herb species.

Management

Direct impacts to floodplain ecosystems (e.g., channelization, road construction, development, filling of wetlands) have greatly altered their composition, structure, and function region-wide. Further impacts that alter riparian function of the remaining areas should be avoided. When development is unavoidable, low impact alternatives (e.g., elevated footpaths, boardwalks, bridges, pervious paving) that maintain floodplain processes should be utilized to minimize impacts to natural areas and the plant and animal species within them. Maintenance of natural buffers surrounding high quality floodplain wetlands is recommended to minimize nutrient runoff, pollution, and sedimentation. Care should also be taken to control and prevent the spread of invasive species into high quality sites. As floodplains are dependent on periodic disturbance, natural flood frequency and duration should be maintained and construction of new dams, levees, or other in-stream modifications should be avoided. Activities resulting in destabilization of the banks or alteration of the disturbance patterns of the site should be avoided. Numerous land use planning recommendations have been proposed to reduce the negative impacts of changing land use on riparian systems. These include protecting riparian buffer habitat, retaining natural areas in developed landscapes, compensating for lost habitat, excluding livestock grazing from riparian areas, providing corridors between riparian and upland habitats, avoiding construction of roads and utility lines through riparian habitat areas, and restoring degraded riparian habitat. In general, unaltered and intact river systems are more resilient to environmental stress than human-impacted or engineered river systems.

Range Map

Pennsylvania Range

This type is found statewide.

Global Distribution

Maryland, New Hampshire, New York, Ohio, Pennsylvania, West Virginia, and potentially in Virginia.

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.

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

NatureServe. 2009. International Ecological Classification Standard: International Vegetation Classification. Central Databases. NatureServe, Arlington, VA. Available http://www.natureserve.org/explorer.

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.

Pennsylvania Natural Heritage Program. 2004. Classification, Assessment and Protection of Non-Forested Floodplain Wetlands of the Susquehanna Drainage. Report to: The United States Environmental Protection Agency and the Pennsylvania Department of Conservation and Natural Resources, Bureau of Forestry, Ecological Services Section. US EPA Wetlands Protection State Development Grant no. CD-98337501.

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.

Zimmerman, E., and G. Podniesinski. 2008. Classification, Assessment, and Protection of Floodplain Wetlands of the Ohio Drainage. Pennsylvania Natural Heritage Program, Western Pennsylvania Conservancy, Pittsburgh, PA. Report to: The United States Environmental Protection Agency and the Pennsylvania Department of Conservation and Natural Resources, Office of Conservation Science. US EPA Wetlands Protection State Development Grant no. CD-973081-01-0.