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Community Field Guide

Scientific Name:
Salix geyeriana / Calamagrostis canadensis Shrubland

Common Name:
Geyer willow / bluejoint reedgrass Shrubland

Community Description

In Colorado, this riparian shrubland often form large expanses of willows on broad montane valley floors. Stands have a 2-3 m tall, cold-deciduous shrub canopy that is dominated by Salix geyeriana. The ground is usually hummocky with a dense herbaceous layer that is dominated by the perennial graminoid, Calamagrostis canadensis. These shrublands are often associated with beaver-created wetlands. Information on stands that occur outside Colorado will be added later.

The Salix geyeriana / Calamagrostis canadensis association can be found in montane habitats in western Montana (from valley bottoms to mid-elevations in the mountains) and in the mountains of central and eastern Montana. It is frequently found on alluvial terraces where beaver activity has created a series of dams that raise the local water table, along streams, and near seeps or springs. Soils are usually deep silt or sand overlying more sand, gravel, or cobbles. This community usually floods during spring, with the water level within 1m of the surface the rest of the year. Nearby wetter communities could include Carex utriculata, Carex aquatilis, Salix geyeriana / Carex utriculata, Typha latifolia, or open water, and nearby drier communities could include Populus balsamifera ssp. Populus trichocarpa / Cornus sericea / Cornus sericea, Calamagrostis canadensis, Deschampsia cespitosa, or Juncus balticus. A variety of adjacent uplands could occur nearby, ranging from conifer dominated communities to dry shrublands such as Artemisia tridentata associations (Hansen et al.1988, Hansen et al. 1995).

The Salix geyeriana / Calamagrostis canadensis association, as it occurs in Montana, has an overstory dominated by Salix geyeriana (40% average cover), which occurs as large clumps; a number of shrub species occur in approximately a third of the stands, including Salix bebbiana, Salix drummondiana, Pentaphylloides floribunda, Ribes spp. About 10% of the stands of Hansen et al. (1995) had Betula nana represented at 20% or higher cover, which occasions speculation as to relative importance of the indicator status of Salix geyeriana and Betula nana. Bog birch is a species strongly associated with peatlands and all the attendant soils related phenomena. These stands have an open corridor aspect, while Salix boothii communities are more often closed and less easily accessible by large ungulates (Padgett et al. 1989). The undergrowth is dominated by Calamagrostis canadensis or Calamagrostis stricta, the two seemingly do not co-occur. If the two Calamagrostis species have low cover values (less than 5%), then Deschampsia cespitosa is used as an indicator but generally its cover and constancy is very low in this association. However, it is decidedly dubious whether this suite of species is actually indicative of a comparable environment. Carex utriculata is the only other native graminoid present in at least 20% of the stands and has low cover, however, a full complement of exotic grasses evidence high constancy and cover, indicating these sites to be livestock impacted. Commonly associated (at least 20% constancy), but by no means indicative, forbs are Aster occidentalis, Epilobium spp., Fragaria virginiana, Geum macrophyllum, Heracleum lanatum, Maianthemum stellatum, Solidago canadensis, and Equisetum arvense (Hansen et al. 1995).

This community or one very similar to it occurs in Montana, Utah, Nevada, and Idaho.

Calamagrostis canadensis is moderately to highly palatable, and with high grazing pressure, the vigor, reproductive success, and competitive ability of this grass will decrease. Exotic pasture grasses (e.g. Poa pratensis, Agrostis stolonifera, Bromus inermis, etc.) will then increase. Livestock grazing in this association should be avoided when the soils are wet to avoid churning of the soil surface. Salix geyeriana / Calamagrostis canadensis stands exposed to heavy browsing pressure usually show reduced vigor of the willow species, such as highlining, clubbing, or dead clumps, with eventual decrease in willow coverage (Hansen et al. 1995).

Global Rank: G5 State Rank: S4

Community References


99-10-15 / J. Greenlee, MTNHP

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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