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CEGL003429 Glyceria grandis Wet Meadow

Type Concept Sentence: No Data Available

Common (Translated Scientific) Name: American Mannagrass Wet Meadow

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: This association most commonly occurs in the mountains of southeastern Oregon, across southern Idaho, and western Montana at elevations ranging from 1340 to 2715 m (4400-8900 feet). The association occurs in narrow to broad V-shaped valleys with 5-6% gradients. It occupies low-lying bars and streamside terraces with silty, slightly acidic soils of saturated alluvium or poorly drained Histosols, Mollisols, and Entisols. The association is also found on the margins of ponds and reservoirs, and in seasonally flooded wet meadows on floodplains of low-gradient streams, springs, sloughs, and ditches. Some occurrences are saturated season-long, while some occurrences are found adjacent to more dynamic fluvial systems that are inundated early in the season. The water table is high and is at or above the soil surface during summer. This association occurs as a very small patch (less than 0.5 acre) but can occupy as much as an entire acre. Stands are distinctively dominated by Glyceria grandis, up to 2 m tall, with an average cover of 30-90%. Other graminoids with high constancy and low cover include Agrostis stolonifera (introduced), Carex athrostachya, Carex vesicaria, Juncus arcticus ssp. littoralis, other Juncus spp., and Eleocharis spp. A variety of forbs that tolerate saturated moisture conditions occur with low cover, including Epilobium spp., Mimulus guttatus, Montia chamissoi, Rumex crispus, and Veronica americana.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: The association is quantitatively defined and described from 6 plots by Evenden (1990), although some stands had high cover of mesic forbs leading to the description of a Glyceria grandis/mesic forb association. These stands are considered synonymous with the Glyceria grandis association based on species composition. Classification is supplemented with 3 plots from Idaho and 2 plots from Montana (Hansen et al. 1988a, Jankovsky-Jones et al. 2001, Hansen and Hall 2002, IDCDC 2002). Kovalchik (2001) lumped 1 plot dominated by Glyceria grandis into the Glyceria striata association. A similar type, ~Schoenoplectus spp. - Poa palustris - Mixed Herbaceous Great Plains Streamside Marsh (CEGL005263)$$, is known from South Dakota and may be synonymous with degraded occurrences of this association. Similar Glyceria borealis and Glyceria striata associations have been described from Idaho, Montana, Oregon, and possibly Wyoming (Hansen et al. 1988a, Crowe and Clausnitzer 1997, and others). These two types are similar to the Glyceria grandis type in the genus of the dominant grass and sometimes in landscape position, hydrology, and associated species. Glyceria grandis is the only species with high cover in this association making stands very distinct in the field. This plant association and closely related types occur in Montana (Hansen et al. 1988a), Idaho (Idaho Conservation Data Center website), and Colorado (Cooper and Cottrell 1990, CNHP 1999).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: No Data Available

Floristics: Vegetation is characterized by a dense herbaceous layer dominated by Glyceria grandis, up to 2 m tall, with an average cover of 30-90%. Other graminoids with high constancy and low cover include Agrostis scabra, Beckmannia syzigachne, Carex aquatilis, Carex athrostachya, Carex nebrascensis, Carex utriculata, Carex vesicaria, Eleocharis acicularis, Eleocharis palustris, Juncus arcticus ssp. littoralis (= Juncus balticus), Juncus orthophyllus, Leersia oryzoides, and Phalaris arundinacea. A variety of forbs that tolerate saturated moisture conditions occur with low cover, including Bidens cernua, Cerastium arvense ssp. strictum, Cerastium fontanum, Epilobium hornemannii, Epilobium ciliatum, Mentha arvensis, Mimulus guttatus, Montia chamissoi, Persicaria spp., Potentilla spp., Rumex crispus, Solidago spp., and Veronica americana. Introduced species are present in disturbed stands and include Agrostis stolonifera, Agrostis gigantea, Alopecurus aequalis, Phleum pratense, and Poa palustris. Sparse cover (<1%) of shrubs such as Salix sp. and Ribes montigenum may be present.

Dynamics:  This plant association is usually stable and long-lived but is susceptible to changes in hydrologic conditions, which will eventually lead to a change in communities (Kittel et al. 1999b).
Environmental Description:  This palustrine wetland association most commonly occurs in the mountains of southeastern Oregon, across southern Idaho, and western Montana and Colorado at elevations ranging from 1342 to 2700 m (4400-8900 feet). The association occurs in narrow to broad V-shaped valleys with 5-6% gradients. Stands are found on the margins of ponds and reservoirs, as well as in permanently and seasonally flooded wet meadows on floodplains of low-gradient streams, springs, sloughs, and ditches where it occupies low-lying bars and streamside terraces, and is often associated with beaver ponds (Evenden 1990, Kittel et al. 1999b, Jankovsky-Jones et al. 2001, Hansen and Hall 2002). Sites are restricted to areas of saturated soils with water levels at or above the soil surface during most of the growing season, but specific soil types and environmental settings can vary among sites. Some occurrences are saturated season-long, while some occurrences are found adjacent to more dynamic fluvial systems that are inundated early in the season. Substrates vary from mineral to organic soils. Soils are coarse to silty, slightly acidic, of saturated alluvium or poorly drained Histosols, Mollisols, and Entisols often forming a highly organic soil of poorly drained muck. This association occurs as a very small patch (less than 0.5 acre) but can occupy as much as an entire acre.
Geographic Range: This relatively uncommon association is known from widely scattered, low- to mid-elevation wetland locations in southeastern Oregon, southern Idaho, western Montana, Colorado and eastern Washington.

Nations: US

States/Provinces:  CO, ID, MT, OR, WA


Confidence Level: High

Confidence Level Comments: No Data Available
Grank: G2?

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.Nb Western North American Temperate Freshwater Marsh, Wet Meadow & Shrubland Division D031 2.C.4.Nb
Macrogroup 2.C.4.Nb.5 Sitka Alder - Booth''s Willow / Northwest Territory Sedge Montane Marsh, Wet Meadow & Shrubland Macrogroup M893 2.C.4.Nb.5
Group 2.C.4.Nb.5.b Sedge species - Reedgrass species Montane Wet Meadow & Marsh Group G521 2.C.4.Nb.5.b
Alliance A3808 American Mannagrass - Fowl Mannagrass - Small Floating Mannagrass Wet Meadow Alliance A3808 2.C.4.Nb.5.b
Association CEGL003429 American Mannagrass Wet Meadow CEGL003429 2.C.4.Nb.5.b
Concept Lineage: No Data Available

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: < Glyceria grandis Dominance Type (Hansen et al. 1988a)
= Glyceria grandis Herbaceous Vegetation (Carsey et al. 2003b)
= Glyceria grandis Herbaceous Vegetation (Carsey et al. 2003a)
= Glyceria grandis Plant Association (Kittel et al. 1999b)
= Glyceria grandis Plant Association (Jankovsky-Jones et al. 2001)
= Glyceria grandis/Mesic Forb Community Type (Evenden 1990)
< Tall Mannagrass Plant Association (Kovalchik 1993) [two plots classified, one dominated by Glyceria grandis and one by Glyceria striata (= Glyceria elata).]
Concept Author(s): A. Evenden (1990)

Author of Description: C. Murphy and K.A. Schulz

Acknowledgements: No Data Available

Version Date: 01-13-05
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