Montana Field Guide

This system is typically associated with highly intermittent or ephemeral streams. It may occur on steep northern slopes or within canyon bottoms where soil moisture and topography produce higher moisture levels than are common throughout most of the area. In some areas of the western Great Plains, in higher elevation draws and ravines, Rocky Mountain juniper (Juniperus scopulorum) can dominate the canopy. Aspen (Populus tremuloides), paper birch (Betula papyrifera), or boxelder maple (Acer negundo) are commonly present in portions of the northwestern Great Plains. In central and eastern Montana, green ash (Fraxinus pennsylvanicus) or chokecherry (Prunus virginiana) are the usual dominants. Douglas hawthorne (Crataegus douglasii) is occasionally seen as a dominant in south-central Montana, especially around the Pryor Mountains. This system is found in ravines formed by ephemeral and intermittent streams, and on toeslopes and north-facing backslopes. Generally, these systems are less than 50 meters (165 feet) wide, although the linear extent may be considerable. Soils are usually deep and loamy. Flooding is very short in duration when it occurs, as water is rapidly channeled downslope.

In Montana, this community is composed mostly of small trees, although larger diameter trees can occur at the foot of the ravine where there is greater available soil moisture. In some areas of the western Great Plains, in higher elevation draws and ravines, Rocky Mountain juniper can dominate the canopy. Aspen, paper birch or boxelder maple are commonly present in portions of the northwestern Great Plains. Throughout central and eastern Montana, green ash or chokecherry are the typical dominants, although Douglas hawthorne is occasionally seen as a dominant in south-central Montana, especially around the Pryor Mountains. Boxelder maple and American elm (Ulmus rubra or Ulmus americana) are often present. In many parts of Montana, particularly in disturbed occurrences, the understory is a dense shrub layer of western snowberry (Symphoricarpos occidentalis). In less disturbed sites, the understory is two-layered, with a shrub layer of chokecherry and other Prunus species, as well as hawthorne species, silverberry (Elaeagnus commutata), current (Ribes species), Woods' rose (Rosa woodsii), and silver buffaloberry (Shepherdia argentea). The lowest layer is dominated by sedges (Carex species) and grasses such as northern reedgrass (Calamagrostis stricta), western wheatgrass (Pascopyrum smithii), bluebunch wheatgrass (Pseudoroegneria spicata), and thickspike wheatgrass (Elymus lanceolatus). Common forbs include American licorice (Glycyrrhiza lepidota), yarrow (Achillea millefolium), meadow rue (Thalictrum dasycarpum), and bedstraw (Galium species). Exotics such as Russian olive (Elaeagnus angustifolia), yellow sweetclover (Meliotus officinalis) and Kentucky bluegrass (Poa pratensis) are often found throughout these systems, especially in agricultural areas.