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Community Field Guide

Scientific Name:
Dulichium arundinaceum Seasonally Flooded Herbaceous Vegetation

Common Name:
Threeway sedge Seasonally Flooded Herbaceous Vegetation

Community Description

This herbaceous vegetation association is known from British Columbia, Canada, the western states of California, Idaho, Montana, Oregon, Washington, and possibly occurs in Wyoming. The community occurs over fibrous peat or mineral soils in areas that are seasonally or permanently flooded with shallow water. In Idaho and Montana stands are typically present in fens and may occur on fixed or floating mats. West of the Cascades it occurs in freshwater marshes as well as in fens. Dulichium arundinaceum may occur as a monoculture, but stands are sometime moderately species-rich with Carex viridula ssp. viridula (= Carex oederi), Carex exsiccata, Carex aquatilis, Carex limosa, Carex lasiocarpa, Eleocharis palustris, Juncus balticus, Lycopus uniflorus, Mentha arvensis, Menyanthes trifoliata, Comarum palustre (= Potentilla palustris), Rhynchospora alba, Schoenoplectus subterminalis (= Scirpus subterminalis), and/or Utricularia macrorhiza (= Utricularia vulgaris) present.

The community occurs over mineral soils, fibrous peat, or muck on areas that are seasonally or permanently flooded with shallow water. In a few places it occurs adjacent to sphagnum peat (Kunze 1994). In Montana this community occurs in depressional wetlands (frequently glacial potholes) and on lake margins (Hansen et al. 1988).

The Dulichium arundinaceum community type is of rare occurrence and poorly described. Dulichium arundinaceum typically occurs as a monoculture with few associated species. Minor amounts of the Eleocharis palustris, Carex aquatilis, Carex limosa, or Carex lasiocarpa may be present. The community occurs on organic soils, on lake margins and may occur on fixed or floating mats (Hansen et al. 1988).

This association is a minor type in the western United States of Montana, Idaho, Oregon, Washington, California and possibly Wyoming. It is also reported from British Columbia, Canada.

Drought years may lower water tables, making this community accessible to both domestic and wild grazing animals; trampling damage by hoofed animals on wet soils may cause rutted and hummock soils on margins. These sites are generally so wet as to preclude most types of recreational uses except fishing.

Global Rank: G3 State Rank: S2

Global Rank Comments:
This plant association is known from the western United States and British Columbia, Canada. Stands are uncommon on the eastern side of the Cascades and more common west of the Cascades. Stands range from small patches in fens to larger occurrences in freshwater marshes. Stands are usually too wet for most uses, but alteration of hydrology and water quality may change species composition. Drought years may make stands accessible to both domestic and wild grazing animals causing rutted and hummocky soils on margins of stands. In addition, loss of waterfowl habitat may concentrate foraging and bedding in stands. Homes and cabins are frequently located along shores of lakes supporting stands. In some locations boat docks are cut into shoreline vegetation, and access across unstable substrates is provided by primitive boardwalks (created with palettes or wood scraps). In addition, nutrients from faulty sewage systems and sediment from activities (roads and logging) within the watershed may impact water chemistry and hydrology. The global rank has been changed from G4?.

Community References


97-01-06 M. Jankovsky-Jones

Bourgeron and Engelking 1994, Bursik and Moseley 1995, Christy 1993, Christy et al. 1998, Driscoll et al. 1984, Kunze 1994, Pierce 1986, Titus and Christy 1999

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This information is from the:
Montana Natural Heritage Program
Montana State Library--Natural Resource Information System
1515 East Sixth Ave., Helena, MT 59620-1800
406 444-5354