Invalid Unit Specified
M302 Acer rubrum - Acer negundo - Platanus occidentalis Eastern North American Ruderal Flooded & Swamp Forest Macrogroup

The U.S. National
Vegetation Classification
Type Concept Sentence: This wetland forest macrogroup is found in northeastern and central United States and southeastern Canada where significant disturbance has greatly altered the species composition and physiognomy of the canopy and understory. Sites are typically flooded for two or more weeks during the growing season.
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Common (Translated Scientific) Name: Red Maple - Box-elder - American Sycamore Eastern North American Ruderal Flooded & Swamp Forest Macrogroup
Colloquial Name: Eastern North American Ruderal Flooded & Swamp Forest
Hierarchy Level: Macrogroup
Type Concept: This macrogroup consists of forested wetlands throughout much of the eastern half of the United States and southern Canada north of Virginia, Tennessee, and Arkansas and east of the Great Plains. Sites where these forests are found have been extensively affected by disturbance such as logging, agricultural use, or a large change in the hydrologic regime. Sites are in depressional wetlands or along the edges of ponds, lakes or rivers. Dominant trees are early-successional native species adapted to wet conditions, especially Acer negundo (exotic in some parts of the range), Acer rubrum, Acer saccharinum, Fraxinus pennsylvanica, and Salix spp. In a few sites, exotic trees such as Acer platanoides, Salix alba, or Salix fragilis may be dominant. The understory is heavily invaded by exotic or invasive native shrub and herbaceous species, including exotics such as Berberis thunbergii (mostly in floodplains and temporarily flooded swamps), Frangula alnus (= Rhamnus frangula), Ligustrum sinense, Ligustrum vulgare, Rhamnus cathartica, and Rosa multiflora (mostly in open floodplains), with occasional generalist native species such as Cornus amomum and Cornus sericea. Herbaceous species may include the exotics Alliaria petiolata (mostly in floodplains), Barbarea vulgaris, Galeopsis spp., Glechoma hederacea, Hesperis matronalis, Hylotelephium telephium, Lysimachia nummularia, Microstegium vimineum (more in floodplains but also basin wetlands), Myosotis scorpioides, Phalaris arundinacea, Phlox paniculata, Phragmites australis, and many others. They may be mixed with very generalist native herbaceous species, such as Calamagrostis canadensis, Cirsium spp., Eupatorium spp., Galium spp., Geum canadense, Glyceria striata, Impatiens capensis, Leersia oryzoides, Solidago canadensis, Solidago rugosa, and Urtica dioica.
Diagnostic Characteristics: This macrogroup includes wetland forests in the eastern United States and southern Canada that have experienced significant hydrologic disturbance or that have been overtaken by exotic species even in the absence of disturbance. This macrogroup is distinguished by having an uneven physiognomy (canopy height, canopy cover) and an understory strongly dominated by exotic and/or invasive native plants. Dominance of these species in the understory is at least 80% relative cover. A few generalist native species may dominate the canopy, including Acer rubrum, Fraxinus pennsylvanica, and Acer negundo.
Rationale for Nominal Species or Physiognomic Features: Nominals are common in this macrogroup but are also common in natural vegetation, so understory shrub and herb species are often what distinguish stands of this macrogroup from native vegetation.
Classification Comments: The current dominant native canopy species are also common in some natural/ruderal swamps. This macrogroup is distinguished by having an uneven physiognomy (canopy height, canopy cover) and an understory strongly dominated by exotic and/or invasive native plants. Only one exotic tree, Acer platanoides, is commonly found in swamps and floodplains in the northern and central United States and this is not typically dominant. It may be that few examples of floodplains have been so altered as to make them unrecognizable as some altered form of other native forest types. Clear specification of the overall set of diagnostic species is needed, not just dominants, along with altered ecological factors, and evidence that native diagnostics are essentially absent (P. Uhlig pers. comm. 2014).

The current definition of this macrogroup requires >80% cover by exotic OR native invasive shrubs and herbaceous species in the understory. This is in agreement with the current concept of ruderal macrogroups (Faber-Langendoen et al. 2014) but a more restrictive concept of the macrogroup requiring >80% relative cover by ONLY exotic shrubs and herbaceous species is favored by some.
Similar NVC Types:
M503 Central Hardwood Swamp Forest, note: tends to have a more even physiognomy and the understory is dominated by native species.
M504 Laurentian-Acadian-North Atlantic Coastal Flooded & Swamp Forest, note: tends to have a more even physiognomy and the understory is dominated by native species.
Physiognomy and Structure: These are tree-dominated wetland forests, but stands can vary from moderately open to closed (25-100% cover) and from short to tall trees. Most stands have a patchy tree canopy and thickets of shrubs. Sites that are recovering from recent extensive disturbance usually have short, young trees and an open canopy with a dense understory. Sites that have not had recent extensive disturbance have taller trees and a moderately closed to closed canopy. The understory in these stands usually thins out due to less light availability, but even most older stands in this wetland forest allow substantial light to penetrate the canopy. A moderate to vigorous shrub and tree sapling layer is typical. The herbaceous layer is extremely variable in cover but tends to have at least moderate cover due to the available light reaching the forest floor.
Floristics: This macrogroup can have a wide variety of native and non-native species. Species composition varies with time since and nature of disturbance, available seed sources, and habitat characteristics, but common dominants in the tree strata are Acer negundo (exotic in parts of the range), Acer rubrum, Acer saccharinum, Fraxinus pennsylvanica, Platanus occidentalis, and Salix nigra. In a few sites, exotic trees such as Acer platanoides, Crataegus spp., Salix alba, or Salix fragilis may be dominant. The understory tree Morus alba can occur on floodplains. The shrub and herb components can have generalist native species but are characterized by exotic and native invasive species providing at least 80% of the lower strata. Shrubs include exotics such as Berberis thunbergii (mostly in floodplains and temporarily flooded swamps), Frangula alnus (= Rhamnus frangula), Ligustrum sinense, Ligustrum vulgare, Rhamnus cathartica, and Rosa multiflora (mostly in floodplains), with occasional generalist native species such as Cornus amomum and Cornus sericea. Herbaceous species range from those also found in wet meadows (more common where the tree canopy allows more light through) to shade-tolerant species. Exotics include Alliaria petiolata (mostly in floodplains), Barbarea vulgaris, Galeopsis spp., Glechoma hederacea, Hesperis matronalis, Hylotelephium telephium, Lysimachia nummularia, Microstegium vimineum (more in floodplains but also basin wetlands), Myosotis scorpioides, Phalaris arundinacea, Phlox paniculata, Phragmites australis, and many others. They may be mixed with very generalist native herbaceous species such as Calamagrostis canadensis, Cirsium spp., Eupatorium spp., Galium spp., Geum canadense, Glyceria striata, Impatiens capensis, Leersia oryzoides, Solidago canadensis, Solidago rugosa, and Urtica dioica (exotic in parts of the range).
Dynamics: These wetland forests are more likely to be affected by further anthropogenic disturbances than natural/ruderal forests. This can include logging or tree clearing of some sort, manipulation of hydrology, continued introduction of seeds of exotic species, etc. In addition, the normal dynamics common to wetland forests can affect examples of this macrogroup. Years of higher or lower than normal precipitation, windthrow, and disease can all affect the composition and physiognomy.
Environmental Description: This macrogroup is found on mineral or shallow peat (<30 cm) soils that are flooded for some or all of the growing season. Soils range from coarse (often alluvial soils) to fine-textured.
Geographic Range: These forested wetlands are found throughout much of the eastern half of the United States and southern Canada north of a line from Virginia to Arkansas and east of the Great Plains.
Nations: CA, US
States/Provinces: CT, DE, IA, IL, IN, KY, MA, MD, ME, MI, MN, MO, NB, NH, NJ, NS, NY, OH, ON, PA, PE, QC, RI, VA, VT, WI, WV
US Forest Service Ecoregions (2007)
Domain Name:
Division Name:
Province Name: Southeastern Mixed Forest Province
Province Code: 231    Occurrence Status: Confident or certain
Section Name: White Mountains Section
Section Code: M211A     Occurrence Status: Confident or certain
Omernik Ecoregions:
Plot Analysis Summary:
Confidence Level: Moderate
Confidence Level Comments:
Grank: GNA
Greasons:
Concept Lineage:
Predecessors:
Obsolete Names:
Obsolete Parents:
Synonomy:
Concept Author(s): Faber-Langendoen et al. (2014)
Author of Description: J. Drake and D. Faber-Langendoen
Acknowledgements: Sean Basquill
Version Date: 05Jun2015
References:
  • Faber-Langendoen, D., J. Drake, S. Gawler, M. Hall, C. Josse, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, L. Sneddon, K. Schulz, J. Teague, M. Russo, K. Snow, and P. Comer, editors. 2010-2017a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]