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Community Field Guide

Scientific Name:
Picea engelmannii / Calamagrostis canadensis Forest

Common Name:
Engelmann spruce / bluejoint reedgrass Forest

Community Description

This forest plant association occurs on cool, moist sites at low to high elevations in the Rocky Mountains of Montana, Wyoming, and southeastern Idaho. It is generally restricted to flat to gently sloping sites with poor drainage, such as fen and lake margins, toeslopes, and low stream and river terraces. This community usually is saturated for a good portion of the year, and stands have a high water table year round. The ground surface in these stands is characterized by a large amount of microtopography stemming from windthrown trees. The overstory is dominated by Picea engelmannii or Picea (engelmannii X glauca) hybrids, and Abies lasiocarpa may also be present. Not infrequently Pinus contorta is a long-persisting seral component. Shrub canopy coverage is low, although the diversity of shrub species present is fairly high. Calamagrostis canadensis and Calamagrostis stricta are diagnostic species when well represented; usually under these shaded forest conditions Calamagrostis canadensis dominates the ground layer, often forming what appears to be a pure grass sward.

The Picea engelmannii / Calamagrostis canadensis plant association occurs as a minor type at low to high elevations in the mountains throughout Montana. It is generally restricted to flat to gently sloping sites with poor drainage, such as fen and lake margins, toeslopes, and low stream and river terraces. Soil texture varies from silt to sandy loam with some redox concentrations present. This community is usually temporarily flooded in the spring, and stands have a high water table year round. Stands are characterized by a conspicuous amount of microtopography stemming from windthrown spruce. Adjacent wetter communities include Salix drummondiana or Betula glandulosa shrublands, or Carex sp. dominated flats. Adjacent drier communities are usually upland conifer forests dominated by Abies lasiocarpa, Pinus contorta, or Pseudotsuga menziesii (Hansen et al. 1995).

The overstory of these typically small stands (several acres at most, frequently a fraction of an acre) is dominated by spruce, Picea engelmannii or hybrids of Picea engelmannii and Picea glauca, (though pure Picea glauca would be diagnostic of a separate alliance). Scattered individuals of Pinus contorta and Abies lasiocarpa may also be present, typically as unthrifty specimens. There is low coverage of shrubs, although the diversity of shrub species present is fairly high. Hansen et al. (1995) specify just 5% or greater cover of Calamagrostis canadensis or Calamagrostis stricta as equivalently diagnostic for this type; usually the cover of either of these species is in excess of 30%. In western Montana, we have noted only Calamagrostis canadensis associated with this community. In the Hansen et al. (1995) dataset 30% of the stands have as much as 40% Carex utriculata; this condition may warrant separation as a distinctly wetter site (different plant association). Associated forb species include Aster occidentalis, Geum macrophyllum, Geranium richardsonii, Solidago canadensis and Equisetum arvense (Hansen et al. 1995).

This community is present in Montana, Idaho, Utah, and Wyoming.

Timber productivity in this type is moderate to high. Because of high water tables, windthrow following harvest is a significant problem, as is soil damage during harvest and site preparation; timing of management activities is important to avoid damage.

Palatability of Calamagrostis canadensis is moderate to high and foliage is most palatable when young. However, wet conditions during this time period make soil susceptible to trampling damage from livestock. If levels of utilization of Calamagrostis canadensis stay high for long periods, production of Calamagrostis canadensis can decline (Hansen et al.1995) and sites can be invaded by exotic graminoids.

Global Rank: G4 State Rank: S4

Global Rank Comments:
This type is the result of merging two associations, with ranks of G3 and G4, resulting in a rank of G4 for this newly defined type. There are a moderate number of estimated occurrences of this community across its range, and apparently the specific hydrologic and geomorphic conditions required for this community are uncommon. Timber harvest has occurred in this community in the past, and this will likely continue; opening the canopy can leave remaining trees (shallowly-rooted) susceptible to blowdown. However, other threats such as exotic species and development are relatively low.

Community References


99-10-18 / 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