Montana Field Guide

This mixed-grass prairie type occurs in Montana primarily in the northeastern and north-central parts of the state in more mesic and productive sites than G331 Great Plains Dry Mixedgrass Prairie. It is much less extensive in the state relative to the Dry Mixedgrass Prairie. It is typically composed of a mix of tall and medium-tall grasses ranging in height from 1 to 3 feet. Shrubs are usually scattered or absent but can form dense, local patches, particularly in swales or low areas. Many Mesic Mixedgrass Prairie sites in Montana were converted to agricultural uses as they are more productive than sites supporting Dry Mixedgrass Prairie. As a result, the remaining sites tend to be more scattered and localized in distribution.

This Group includes the more mesic communities of the Great Plains Mixedgrass Prairie Ecological System.

Medium and Tallgrass Prairie; Warm Season Grasses; Grasses >25% Cover; Great Plains Region; Mesic sites; Mesic, Shrubby Sites

Dominants: Big Bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans) Western Porcupine Grass (Stipa curtiseta) Little Bluestem (Schizachyrium scoparium), Green Needlegrass (Stipa viridula), Western Wheatgrass (Elymus smithii), Switchgrass (Panicum virgatum) and the medium to tall shrubs: Hawthorns (Crataegus spp.), Serviceberry (Amelanchier alnifolia), Silverberry (Elaeagnus commutata), Silver Buffaloberry (Shepherdia argentea), Chokecherry (Prunus virginiana) and Western Snowberry (Symphoricarpos occidentalis)

This Group occurs in the Great Plains of eastern Montana extending west in scattered patches into north-central Montana. It is most abundant in Daniels, Dawson, Richland, Roosevelt, Sheridan, and Wibaux Counties. Minor patches may occur throughout the Great Plains in mesic sites, such as swales and on northerly aspects in what is otherwise dry mixedgrass prairie.

In Montana, G141 occurs in Level III Ecoregions 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).

In Montana, G141 occurs or potentially occurs within these Major Land Resource Areas: 52 - Brown Glaciated Plains; 53A - Northern Dark Brown Glaciated Plains; 53B - Central Dark Brown Glaciated Plains; 54 - Rolling Soft Shale Plain, and 58A - Northern Rolling High Plains, Northern Part.

Large Patch-Matrix

This group occurs on a wide variety of landforms and in proximity to a diversity of other groups. Climate and growing season length for the region in which it occurs are intermediate to the shortgrass regions to the west and southwest and the tallgrass regions to the east. Soils range from loams, clay loams, silty clays, and clays to more coarse-textured sandy or gravelly soils. Some sites may include an impermeable or semi-permeable, claypan, subsoil layer.

This group is dominated by medium to tall grasses in the western Great Plains, particularly mid-height species such as Green Needlegrass (Stipa viridula), Western Wheatgrass (Elymus smithii), Little Bluestem (Schizachyrium scoparium) and Western Porcupine Grass (Stipa curtiseta), and tallgrasses such as Big Bluestem (Andropogon gerardii), Switchgrass (Panicum virgatum), and Indiangrass (Sorghastrum nutans). Grass cover is generally moderate to dense. Other graminoids such as Prairie Junegrass (Koeleria macrantha), Idaho Fescue (Festuca idahoensis) and Carex inops ssp heliophila are common components in some sites. The group also includes mesic, shrub-dominated sites. Species such as Hawthorns (Crataegus spp.), Serviceberry (Amelanchier alnifolia), Silverberry (Elaeagnus commutata), Silver Buffaloberry (Shepherdia argentea), Chokecherry (Prunus virginiana) and Western Snowberry (Symphoricarpos occidentalis) are the typical dominants or co-dominants. Patches are generally small but are dictated by topographic constraints. Shrub heights are generally 1-3 meters.

In Montana, this group is represented by 5 Alliances and 17 Associations within the National Vegetation Classification. These likely cover the range of vegetation types within this group in Montana.

Fire and grazing constitute the primary dynamics affecting this group. Drought can also impact it, in general favoring the shortgrass component at the expense of the midgrasses. With intensive grazing, cool-season exotics such as Kentucky Bluegrass (Poa pratensis) and annual bromes can increase in dominance. Shrub species can also increase in dominance with fire suppression. Conversion to agriculture has substantially decreased the extent of this group in Montana as these sites have higher productivity than other prairie sites.

S. Menard and J. Drake 2015

S. Mincemoyer

12/4/2024