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G046 Thuja occidentalis - Fraxinus nigra - Acer rubrum Swamp Forest Group
Type Concept Sentence: These forested wetlands are dominated by Thuja occidentalis often with Acer rubrum or Fraxinus nigra and found on circumneutral to alkaline soils across the temperate regions of eastern to south-central Canada south into northern New England and the upper Midwest and down to the high plateau of the Allegheny Mountains.
Common (Translated Scientific) Name: Northern White-cedar - Black Ash - Red Maple Swamp Forest Group
Colloquial Name: Laurentian-Acadian Alkaline Swamp
Hierarchy Level: Group
Type Concept: These forested wetlands are found across the temperate regions of eastern to south-central Canada, southward from northern New England to the upper Midwest and down to the high plateau of the Allegheny Mountains. They occur in areas where circumneutral to alkaline pH and/or higher nutrient levels are associated with a rich flora. Examples of this group also occur within swales along the dunes of the Great Lakes. The substrate is typically mineral soil, but there may be extensive peat in examples occurring on the margins of peatland complexes. Thuja occidentalis is a diagnostic canopy species and may dominate the canopy or be mixed with other conifers or with deciduous trees, most commonly Acer rubrum or Fraxinus nigra. Some examples are strongly dominated by deciduous hardwoods, such as Fraxinus nigra (less often Fraxinus americana) and Acer rubrum. Larix laricina, a deciduous conifer, may dominate some stands within this group. Shrub species commonly occur and range in cover from sparse to dense depending on canopy cover. The herb layer tends to be more diverse than in acidic swamps and some examples may have extensive bryophytes. Examples of this group may occur on seepages, in a basin setting, or alluvial settings. A hummock-and-hollow topography is typical. Logging, especially of Thuja occidentalis, has influenced the structure and dominance of many examples of this group.
Diagnostic Characteristics: This type is distinguished by the poorly drained, circumneutral to alkaline conditions with a hummock-and-hollow topography, shallow to deep layer of peat (20+ cm) in combination with a mix of sphagnum, feathermosses and brown mosses, a variable tall-shrub layer of Alnus incana, Ilex verticillata, and Vaccinium corymbosum, with occasional ericaceous shrubs, and partial to closed tree canopies, ranging from pure conifer to deciduous, with dominants of Thuja occidentalis, Acer rubrum, and Fraxinus nigra. Other temperate species companions include Tsuga canadensis, Picea rubens, and Betula alleghaniensis.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Analyses of FIA plot data from the eastern U.S. combined this group and ~Laurentian-Acadian Acidic Swamp Group (G045)$$ into a Northern White-cedar - Hemlock - Red Spruce Conifer Swamp Group (Faber-Langendoen and Menard 2006). On review, this FIA group was split based on broad patterns of substrate pH, with this group (G046) housing the more alkaline swamps and G045 housing the more acidic swamps. Thuja occidentalis is a diagnostic here, but can also be diagnostic for boreal rich swamps, so further clarity is needed on the distinction between boreal rich swamps in ~Ontario-Québec Boreal Flooded & Rich Swamp Forest Group (G809)$$ and ~Atlantic Boreal Flooded & Rich Swamp Forest Group (G810)$$ and this type, but in this northern rich swamp type Thuja occidentalis often has companions of Tsuga canadensis, Picea rubens, Betula alleghaniensis, and Acer rubrum, which are not typically found in boreal rich swamps.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This group contains mostly closed-canopy to patchy-canopy forests. Many examples contain a hummock-and-hollow topography. Dominant species can range from completely deciduous to completely coniferous. The most common canopy structure is mixed. The shrub layer varies from sparse to well-developed depending on the canopy cover, but some shrub cover is typical. Herb cover likewise varies. The bryoid layer is often extensive.
Floristics: The canopy layer varies from very open to moderately closed. Typical examples of this group are mixed conifer and deciduous with Thuja occidentalis being the most common conifer species and Fraxinus nigra the most common deciduous species. Typical stands contain a hummock-and-hollow topography with Thuja occidentalis dominating the hummocks and Fraxinus nigra common in the hollows. Some examples are dominated by conifers in addition to Thuja occidentalis, most commonly Larix laricina, although some examples may contain Picea spp. The density of shrubs varies with canopy closure. The most common are minerotrophic shrubs such as Cornus sericea and Alnus incana; Rhamnus alnifolia is a good indicator species. The herbaceous layer is typically more diverse than acidic swamps. It is characterized by Carex spp., Linnaea borealis, and Lonicera spp. An incomplete to dense moss layer occurs.
Dynamics: Tip-up mounds caused by blowdowns are common, in part because the very wet soils permit only shallow rooting by Thuja occidentalis. Logging, especially of Thuja occidentalis, has influenced the structure and dominance of this group. Acreage of hardwood-conifer swamp has been reduced by conversion of wetlands for agriculture and other human uses (Kost et al. 2007).
Environmental Description: Stands occur on level to gently sloping ground with wet, organic or mineral soil. Typical stands occur along the margins of peatlands, in drainage courses, shores of lakes and rivers above flooding level, or in shallow depressions. Some examples occur in swales within dunal areas of the Great Lakes. Stands occur on wet, saturated soils. Substrate is either wet mineral soils or well-decomposed peat, and hummocky topography is present. The groundwater is moderately minerotrophic and has circumneutral to alkaline pH.
Geographic Range: This group is located in northern New England and the Midwest, and southern regions of eastern and central Canada. It ranges into the southern Great Lakes and south-central Minnesota south to northern Illinois, Indiana, Ohio, and West Virginia. Examples are can be found along the high, flat plateau of the Allegheny Mountains.
Nations: CA,US
States/Provinces: CT, DE, IL, IN, MA, MB, MD, ME, MI, MN, NB, ND, NH, NJ, NY, OH, ON, PA, QC, RI, VT, WI, WV
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.836789
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: No Data Available
- Comer, P., and D. Albert. 1993. A survey of wooded dune and swale complexes in Michigan. Michigan Natural Features Inventory, Natural Heritage Program. Lansing, MI. 158 pp.
- 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. 2010-2019a. Divisions, Macrogroups and Groups for the Revised U.S. National Vegetation Classification. NatureServe, Arlington, VA. plus appendices. [in preparation]
- Faber-Langendoen, D., and S. Menard. 2006. A key to eastern forests of the United States: Macrogroups, groups, and alliances. September 15, 2006. NatureServe, Arlington, VA.
- Kost, M. A., D. A. Albert, J. G. Cohen, B. S. Slaughter, R. K. Schillo, C. R. Weber, and K. A. Chapman. 2007. Natural communities of Michigan: Classification and description. Report No. 2007-21, Michigan Natural Features Inventory, Lansing. 314 pp. [http://web4.msue.msu.edu/mnfi/reports/2007-21_Natural_Communites_of_Michigan_Classification_and_Description.pdf]