Common (Translated Scientific) Name: Pin Oak - Green Ash - Blackgum Swamp Forest Macrogroup
Colloquial Name: Central Hardwood Swamp Forest
Hierarchy Level: Macrogroup
Type Concept: These swamp forests include seepage, wet flatwood and depression, and lake or pond fringe forests (i.e., not associated with overbank flow from stream or river channels) found in the eastern United States and adjacent Canada, primarily exclusive of the coastal plains. Stands are dominated by hardwood trees, including Acer rubrum var. trilobum, Acer saccharinum, Betula nigra, Fagus grandifolia, Fraxinus pennsylvanica, Liriodendron tulipifera, Liquidambar styraciflua, Nyssa biflora, Nyssa sylvatica, Platanus occidentalis, Quercus alba, Quercus bicolor, Quercus lyrata, Quercus michauxii, Quercus palustris, and Quercus phellos. The collective range includes the northern glaciated midwestern United States ranging east into Lower New England, south into most of the south-central states, including the broad Appalachian region, the unglaciated Interior Low Plateau, and the Ouachitas and Ozarks. Examples of ~Central Interior-Appalachian Seepage Swamp Group (G044)$$ generally occur where the substrate is saturated to the surface for extended periods during the growing season, but where surface water is seldom present for more than short periods of time. This includes streamhead swales or broad sandstone ridges where soils are sandy and saturated due to a combination of perched water table and seepage flow, as well as seepage-fed wetlands on gentle slopes, with substantial seepage flow which may be influenced by wildland fire, and along the bottom slopes of smaller valleys, as well as in the upper riparian zones of larger creeks, sometimes extending upslope along small ephemeral drainages. Examples of ~South-Central Flatwoods & Pond Forest Group (G654)$$ are found in ponds, wet depressions, flats along small streams, and other related environments. Examples of ~Central Hardwood Swamp & Flatwoods Forest Group (G597)$$ are found in ponds and depressions, and include various kinds of flatwoods (where soils often contain an impermeable clay layer or fragipan creating a shallow, perched water table, soils are poorly drained to very poorly drained, and surface water may be present for extended periods of time, rarely becoming dry).
Diagnostic Characteristics: These are generally nonriverine forested wetlands, characterized by hydrologic setting, which includes flat to depressional wetlands, as well as seepage swamps, ponds, flats along small streams, and other related environments. Stands are dominated by a diverse suite of primarily wetland Quercus species or other wetland deciduous hardwood trees that vary with biogeography and hydrology. Diagnostic species include Acer rubrum var. trilobum, Fagus grandifolia, Fraxinus pennsylvanica, Liriodendron tulipifera, Liquidambar styraciflua, Nyssa biflora, Nyssa sylvatica, Platanus occidentalis, Quercus alba, Quercus bicolor, Quercus lyrata, Quercus michauxii, Quercus palustris, and Quercus phellos.
Rationale for Nominal Species or Physiognomic Features: Quercus palustris represents a northern component. Quercus michauxii would be an equivalent southern component, but it is not used as a nominal. Their ranges lack any substantial overlap. Fraxinus pennsylvanica and Quercus palustris are wide-ranging swamp tree species whose ranges primarily define the range of the macrogroup.
Classification Comments: The floristic and hydrologic variation within this diverse macrogroup will be accommodated by the various component groups and alliances.
Similar NVC Types:
M302 Eastern North American Ruderal Flooded & Swamp Forest, note:
M504 Laurentian-Acadian-North Atlantic Coastal Flooded & Swamp Forest, note:
Physiognomy and Structure: Stands of this macrogroup are composed of broad-leaved deciduous trees. The canopy can range from moderate to dense. The density of shrubs and herbs varies based on the extent of canopy closure, hydrologic regime, and disturbance regime. In the current landscape, most are closed-canopy forests, but with greater fire frequencies they would have varied more in the past.
Floristics: Stands are dominated by hardwood trees, typical of wet-mesic to wet conditions, including Acer rubrum var. trilobum, Acer saccharinum, Betula nigra, Fagus grandifolia, Fraxinus pennsylvanica, Nyssa sylvatica, Liriodendron tulipifera, Liquidambar styraciflua, Nyssa biflora, Platanus occidentalis, Quercus alba, Quercus bicolor, Quercus lyrata, Quercus michauxii, Quercus palustris, and Quercus phellos. Understories and ground layers vary with biogeography and hydrology, but some possible shrub components include Alnus serrulata, Carpinus caroliniana, Cephalanthus occidentalis, Ilex opaca var. opaca (central), Leucothoe racemosa (= Eubotrys racemosa), Lyonia lucida, Vaccinium corymbosum, and Viburnum nudum. The herb layer is quite variable. Forbs such as Boehmeria cylindrica, Impatiens capensis, Rudbeckia laciniata, and Saururus cernuus (central) are also often prominent with various wetland grasses, sedges, and rushes, including Carex albolutescens, Carex intumescens, Carex joorii, Chasmanthium laxum, Cinna arundinacea, and others. Large wetland ferns such as Osmunda cinnamomea and Osmunda regalis var. spectabilis are often prominent. Large Smilax tangles sometimes occur, and some examples have substantial amounts of Sphagnum spp. There is some floristic variation with latitude and elevation, with southern and lower-elevation associations containing Magnolia virginiana and/or Nyssa biflora, which are more typical of the coastal plain. In drier examples, Quercus rubra, Quercus stellata, and/or Quercus velutina may occur. Other species (in drier zones or phases) include Campsis radicans, Cardamine bulbosa, Croton willdenowii, Danthonia spicata, Leersia virginica, Manfreda virginica, Porteranthus stipulatus, and Pycnanthemum tenuifolium.
Dynamics: In ~Central Interior-Appalachian Seepage Swamp Group (G044)$$, the presence of seepage is the most important environmental factor. Long-term droughts will affect seepage flow and presumably have an impact on the vegetation. Canopy dynamics are not well-known and potentially may vary substantially over short distances in response to wetness. Wetness clearly limits recruitment of most tree and shrub seedlings to drier microsites in the wettest examples, and fire is also important in some examples. Long-term geomorphic processes may also be important. Headward erosion by small streams, or meandering by larger stream channels, sometimes drains seeps and eliminates the wetland vegetation. In north-central swamps and flatwoods (~Central Flatwoods & Swamp Forest Group (G597)$$), water level dynamics are the most important factor, differentiating them from the surrounding uplands and differentiating the various components from one another. Most depressions and basins have a very limited watershed area, so water comes largely from rainfall. Variation in rainfall patterns will drive variation in duration of flooding, though most basins have an outlet that ultimately limits water depth. Fire is presumably naturally rare in these systems, although they would naturally be exposed to fires spreading from the surrounding uplands. Standing water and lack of continuous fuel would limit fires to the edges of ponds, with greater influence in flatwoods.
Environmental Description: This wooded wetland vegetation encompasses various primarily non-alluvial wetlands of the eastern and central United States. This diverse suite of communities includes types associated with ponds and depressions, as well as various kinds of flatwoods. Flatwoods often contain an impermeable clay layer or fragipan creating a shallow, perched water table, soils are poorly drained to very poorly drained, and surface water may be present for extended periods of time, rarely becoming dry. These wetlands result from topographic or edaphic circumstances that promote an enhanced hydroperiod at these sites, and this affects both the vegetation and the dynamics. Ponds and flatwoods have some features in common, and are united at this level, but will be discussed separately where this is necessary. Examples of ~Central Interior-Appalachian Seepage Swamp Group (G044)$$ occur in small patches where relatively constant or seasonal seepage water creates wetland conditions. This seepage commonly occurs at the base of slopes on the edge of bottomlands or in headwaters of small streams. Examples also occur on gently sloping hillsides where impermeable soils and slope force shallow groundwater to the surface. The soils are seasonally to permanently saturated, but without substantial standing water. In north-central swamps and flatwoods (~Central Flatwoods & Swamp Forest Group (G597)$$), soils are poorly drained to very poorly drained, and may have a dense clay hardpan or some other impermeable clay layer or fragipan that limits internal drainage and can create a shallow, perched water table. Some soils may be deep (100 cm or more), consisting of peat or muck. Rainwater accumulates in the basins and persists through the wet season, occasionally persisting all year. Some examples become dry, with drought possible during the summer and autumn months. These fluctuating moisture levels can lead to complexes of forest upland and wetland species.
Geographic Range: The collective range includes the northern glaciated midwestern United States and adjacent Canada, ranging east into Lower New England, south into most of the south-central states, including the broad Appalachian region, including the Piedmont, from Alabama to Kentucky, and the Ouachitas and Ozarks of Arkansas and Oklahoma.
Nations: CA, US
States/Provinces: AL, AR, CT, DC?, DE, GA, IA, IL, IN, KY, MA, MD, MI, MO, NC, NH, NJ, NY, OH, OK?, ON, PA, QC, RI, SC, TN, VA, WV
|US Forest Service Ecoregions (2007)|
Ouachita Mixed Forest - Meadow Province
Confident or certain
Western Unglaciated Allegheny Plateau Section
Confident or certain
Confidence Level: Moderate
Confidence Level Comments:
Concept Author(s): Faber-Langendoen et al. (2014)
Author of Description: M. Pyne
Acknowledgements: We have incorporated significant descriptive information previously compiled by S. Menard and S. Gawler.
Version Date: 15Oct2014
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