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Community Field Guide

Scientific Name:
Scirpus acutus Herbaceous Vegetation

Common Name:
Hardstem bulrush Marsh

Community Description

This association is a common emergent herbaceous wetland found mostly in the interior western U.S. ranging from the Puget Sound of Washington to Montana south to California, Nevada and Utah. Stands occur along low-gradient, meandering, usually perennial streams, river floodplain basins, and around the margins of ponds and shallow lakes especially in backwater areas. Some sites are flooded most of the year with about 1 m of fresh to somewhat saline or alkaline water. Other sites, however, dry up enough in late summer to where the water table drops below the ground surface, though the soils are still partially saturated. Soils are generally deep, organic, alkaline, poorly drained and fine-textured, but range in soil textures from sand to clay to organic muck. The soils may be normal or saline. Vegetation is characterized by a dense tall herbaceous vegetation layer 1-3 m tall that is dominated by Schoenoplectus acutus (= Scirpus acutus), often occurring as a near monoculture. Associated species include low cover of Mentha arvensis, Polygonum amphibium, Sagittaria latifolia, and species of Carex, Eleocharis, Rumex, and Typha. Early in the growing season or at permanently flooded sites, aquatic species such as Potamogeton spp. and Lemna minor may be present to abundant. Stands of this association contain no tree or shrub layer, but a few sites have been invaded by the introduced shrub Tamarix spp.

Stands of this community type occur along the margins of ponds, lakes, and reservoirs, stringers paralleling stream and river channels, or broad swaths in backwater marshes and sloughs. It is found at low to mid-elevations, from about 2,000 feet to at least 6,600 feet. This type often inhabits relatively deep water, although the water level may be drawn down considerably through the growing season (Hansen et al. 1995; Hall and Hansen 1997). Soils are commonly Mollisols (Aquolls), Entisols (Aquents), or occasionally Histisols. Textures of surface horizons on long-lived stands are predominantly fines, which appear as black or gleyed, mucky clay or silty loam soils with high concentrations of decomposed and partially decomposed plant material that accumulate over time from annual dieback. Alluvial sands, gravel and cobbles may form an unconsolidated matrix in the subsurface horizons. Water tables are generally at or above the soil surface throughout the growing season. Soil reaction varies from neutral to moderately alkaline (pH 7.0 to 8.0)(Hansen et al. 1995; Hall and Hansen 1997).

The Scirpus acutus type usually appears as an impenetrable monotypic stand often reaching 2 m or more in height. Scirpus ssp. require high levels of moisture throughout the year, and while stands may colonize saturated soils along streambanks or on the periphery of ponds and reservoirs, they typically extend out into the water column to 2 m in depth. Due to the dense growth form and flooded water regimes, other species are largely absent, or if present, in limited amounts (Cole 1995; Hansen et al. 1995; Hall and Hansen 1997).

Stands are known from Oregon, Washington, Nevada, California, Idaho, Colorado, and Montana.

Wet conditions and lack of palatable forage limit livestock use of this type. However, if upland forage becomes sparse and soil conditions dry, livestock may make use of Scirpus acutus. Soils are wet throughout the growing season and are easily damaged from trampling by livestock and wildlife. Trampling can also damage vegetation. This community will burn in either late fall or early spring if the water levels have dropped sufficiently (Hansen et al. 1995).

Global Rank: G5 State Rank: S5

Community References


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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