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A3647 Carex torta - Mixed Forb Riverbed Alliance

Type Concept Sentence: This herbaceous vegetation, ranging from Alabama north to northern New England and southern Quebec, occurs on large coarse substrates deposited along medium- to high-energy river channels and, less frequently, exposed lakeshores with heavy wave action. Vegetation can be sparse to dense depending on degree of flooding and length of exposure, with Carex torta and low Salix spp. as the characteristic species.

Common (Translated Scientific) Name: Twisted Sedge - Mixed Forb Riverbed Alliance

Colloquial Name: Twisted Sedge - Mixed Forb Riverbed

Hierarchy Level:  Alliance

Type Concept: This herbaceous vegetation occurs on large coarse substrates deposited along medium- to high-energy river channels and, less frequently, exposed lakeshores with heavy wave action. Seasonal flooding and ice-scour maintain the open nature of these communities; generally, they develop in areas of the active channel that are exposed at low water or in drought years. Vegetation can be sparse to dense depending on degree of flooding and length of exposure. Characteristic perennial species that tolerate inundation and flood-scouring include Carex torta and low Salix spp. Associated species tend to vary widely from site to site, can be diverse, and may be sparse. Associated species vary with geography. In the Allegheny Mountains, associated species include Doellingeria umbellata, Dichanthelium clandestinum, Solidago rugosa ssp. aspera, Juncus effusus var. solutus, Scirpus expansus, Scirpus cyperinus, Equisetum arvense, Onoclea sensibilis, Vernonia noveboracensis, Lycopus virginicus, Scutellaria lateriflora, and Salix sericea. In Southern Appalachian gorges, this vegetation often is associated with ~Alnus serrulata - Xanthorhiza simplicissima Wet Shrubland (CEGL003895)$$. In the Cumberland Plateau of Alabama, herbaceous components may include Lobelia cardinalis, Symphyotrichum dumosum, Lycopus virginicus, Osmunda regalis, and Hypericum mutilum. Physiognomy varies from strictly herbaceous to shrubby to wooded herbaceous. Scattered shrubs and small, battered specimens of Platanus occidentalis, Betula nigra, Cornus amomum, Alnus serrulata, and Carpinus caroliniana are present in some stands. Stands in disturbed landscapes may be heavily invaded by Microstegium vimineum, Polygonum cespitosum var. longisetum, and other weedy exotics.

Diagnostic Characteristics: Dominance by Carex torta on rivershores scoured by high-energy flooding.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: Additional classification work may suggest splitting this alliance.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Stands of this alliance are characterized by light-requiring, tough-rooted herbaceous perennials tolerant of frequent inundation and flood-scouring, which often form dense, extensive colonies.

Floristics: Carex torta often forms dense, extensive colonies. Associated species in the Allegheny Mountains include Doellingeria umbellata (= Aster umbellatus), Dichanthelium clandestinum, Solidago rugosa ssp. aspera, Juncus effusus var. solutus, Scirpus expansus, Scirpus cyperinus (= var. pelius), Equisetum arvense, Onoclea sensibilis, Vernonia noveboracensis, Lycopus virginicus, Scutellaria lateriflora, and Salix sericea. In Southern Appalachian gorges this vegetation often is associated with ~Alnus serrulata - Xanthorhiza simplicissima Wet Shrubland (CEGL003895)$$. In the Cumberland Plateau of Alabama, herbaceous components may include Lobelia cardinalis, Symphyotrichum dumosum (= Aster dumosus), Lycopus virginicus, Osmunda regalis, and Hypericum mutilum. Scattered shrubs and small, battered specimens of Platanus occidentalis, Betula nigra, Cornus amomum, Alnus serrulata, and Carpinus caroliniana are present in some stands. Stands in disturbed landscapes may be heavily invaded by Microstegium vimineum, Polygonum cespitosum var. longisetum, and other weedy exotics.

Dynamics:  Stands of this alliance are characterized by light-demanding, tough-rooted herbaceous perennials that are able to withstand frequent inundation and flood-scouring. Periodic large or severe floods transport and deposit large numbers of cobbles, stones, and even boulders in characteristic bars both within the channel (islands) and along its edges (streambanks). These bars provide a matrix for deposition of finer alluvium and habitats for the establishment of tough, adaptable herbaceous plants, which in turn stabilize the bars with massive networks of perennial rootstocks. Regular flood-scouring batters or removes woody plants which take root in these habitats, maintaining open-canopy conditions. These habitats are highly dynamic, with conditions more or less constantly shifting in response to an irregular but powerful disturbance regime. While some of the bar habitats may be damaged or removed by severe floods, others may accrete or be newly deposited during the same events (Hupp 1982). Successionally, this unit can be considered a pioneering type on new, coarse alluvial land, but it is also more or less permanently maintained by natural disturbances.
Environmental Description:  This alliance includes sedge-dominated alluvial wetlands on sand, gravel, and rock bars in valleys and gorges.
Geographic Range: This alliance has a broad geographic range, from Alabama north to northern New England and southern Quebec.

Nations: CA,US

States/Provinces:  AL, CT, DE, GA, KY, MA, MD, ME, NC, NH, NY, PA, QC, RI, SC, TN, VA, VT, WV


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: GNR

Greasons: No Data Available
Type Name Database Code Classification Code
Class 2 Shrub & Herb Vegetation Class C02 2
Subclass 2.C Shrub & Herb Wetland Subclass S44 2.C
Formation 2.C.4 Temperate to Polar Freshwater Marsh, Wet Meadow & Shrubland Formation F013 2.C.4
Division 2.C.4.Nd Eastern North American Temperate Freshwater Marsh, Wet Meadow & Shrubland Division D323 2.C.4.Nd
Macrogroup 2.C.4.Nd.3 Eastern North American Wet Shoreline Vegetation Macrogroup M880 2.C.4.Nd.3
Group 2.C.4.Nd.3.a Eastern North American Riverine Wetland Vegetation Group G755 2.C.4.Nd.3.a
Alliance A3647 Twisted Sedge - Mixed Forb Riverbed Alliance A3647 2.C.4.Nd.3.a
Association CEGL004103 Twisted Sedge Riverbed Vegetation CEGL004103 2.C.4.Nd.3.a
Association CEGL006536 Twisted Sedge - Indian-hemp - Flatsedge species Riverbed Vegetation CEGL006536 2.C.4.Nd.3.a
Concept Lineage: A.1340, in part

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: >< IIE3a. Riverside Shoal and Stream Bar Complex (Allard 1990)
Concept Author(s): L. Sneddon, in Faber-Langendoen et al. (2013)

Author of Description: L. Sneddon and D. Faber-Langendoen

Acknowledgements: No Data Available

Version Date: 12-18-14
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  • Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
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  • Hupp, C. R. 1982. Stream-grade variation and riparian forest ecology along Passage Creek, Virginia. Bulletin of the Torrey Botanical Club 109:488-499.
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  • Tobe, J. D., J. E. Fairey, III, and L. L. Gaddy. 1992. Vascular flora of the Chauga River Gorge, Oconee County, South Carolina. Castanea 57:77-109.