Montana Field Guide

This group is typically associated with intermittent or ephemeral streams in the Great Plains and commonly dominated by American Elm (Ulmus americana) or Green Ash (Fraxinus pennsylvanica). These communities occur on northerly slopes or within the bottoms of draws and ravines where topography produces higher moisture levels than commonly found in the surrounding area. Tree canopy cover is variable, ranging from open to closed and trees are often short (<30ft tall). In some areas of the western Great Plains, Rocky Mountain Juniper (Juniperus scopulorum) may dominate the canopy. Quaking Aspen (Populus tremuloides), Paper Birch (Betula papyrifera), or Boxelder (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. Hawthorns (Crataegus spp) are occasionally seen as dominant species in some areas. This group is often found in ravines formed by ephemeral and intermittent streams, and on toeslopes and north-facing slopes. Generally, these communities are less than 50 meters (165 feet) wide, although the linear extent may be considerable. Soils are usually deep and loamy. Stands of this group that occur on upper terraces and toeslopes in riparian areas are rarely flooded but have root access to groundwater.

This Group encompasses a portion of the Great Plains Wooded Draw and Ravine Ecological System.

Deciduous Forest and Woodland; Great Plains Region; Upper River Terraces, Protected Slopes (often north-facing), Ravines, and Draws.

Typical Dominants: American Elm (Ulmus americana), Green Ash (Fraxinus pennsylvanica)

This Group occurs across the Great Plains in Montana, especially in the eastern portion where American Elm is present. It may be found within the Milk, Missouri and Yellowstone River drainages.

In Montana, G145 occurs in Level III Ecoregions 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).

In Montana, G145 occurs within these Major Land Resource Areas: 52 - Brown Glaciated Plains, 53A - Northern Dark Brown Glaciated Plains, 53B - Central Dark Brown Glaciated Plains, 58 - Northern Rolling High Plains, and potentially in 60A - Pierre Shale Plains and 60B - Pierre Shale Plains, Northern Part

Small Patch

This group is typically associated with intermittent or ephemeral streams within the bottoms of draws and ravines or on northerly slopes where topography produces higher moisture levels than are commonly found throughout the surrounding area. Communities are best developed under conditions that favor snow entrapment, development of deeper soils, and concentration of moisture. These conditions are typical of ravines formed by ephemeral and intermittent streams and on toeslopes and north-facing slopes. Generally, these systems are less than 50 meters (165 feet) wide, although the linear extent may be considerable. Soils are usually deep loams. Stands of this group that occur on upper terraces and toeslopes in riparian areas are rarely flooded but have root access to groundwater. Flooding is very short in duration when it occurs, as water is rapidly channeled downslope. Similar communities that occur on well-developed floodplains that are more regularly flooded are part of G147 Great Plains Floodplain Forest. Adjacent uplands are generally Great Plains mixed grass prairies and shrublands.

This group is commonly dominated by American Elm (Ulmus americana) or Green Ash (Fraxinus pennsylvanica). In some areas, Rocky Mountain Juniper (Juniperus scopulorum) may dominate or co-dominate the canopy. Quaking Aspen (Populus tremuloides), Paper Birch (Betula papyrifera), and Boxelder (Acer negundo) are common associates. Hawthorns (Crataegus spp) are occasionally seen as dominants in some areas. Tree canopy cover is variable, ranging from open to closed and trees are often short (<30ft tall) in stature.

Chokecherry (Prunus virginiana) and western Snowberry (Symphoricarpos occidentalis) are common shrubs components. In many parts of eastern Montana, particularly in disturbed settings, the understory is a dense shrub layer of Western Snowberry. In less disturbed sites, the understory is two-layered, with a shrub layer of Chokecherry and other Prunus species, as well as Hawthorne, Silverberry (Elaeagnus commutata), Currant and Gooseberry (Ribes spp), Woods' Rose (Rosa woodsii), and Silver Buffaloberry (Shepherdia argentea). The lowest layer is dominated by Sedges (Carex species) and grasses such as Western Wheatgrass (Elymus smithii), Bluebunch Wheatgrass (Elymus spicatus), and Thickspike Wheatgrass (Elymus lanceolatus). Common forbs include American Licorice (Glycyrrhiza lepidota), Yarrow (Achillea millefolium), Purple Meadowrue (Thalictrum dasycarpum), Starry False Solomon's-seal (Smilacina stellata) and Bedstraw (Galium spp). Exotics such as Russian olive (Elaeagnus angustifolia), Yellow Sweetclover (Meliotus officinalis), Kentucky Bluegrass (Poa pratensis), Smooth Brome (Bromus inermis) and Leafy Spurge (Euphorbia virgata) are often present, especially near agricultural settings.

Alliances and Associations in this group within the National Vegetation Classification are poorly documented with only one alliance and one association currently described or attributed to Montana.

Livestock use and invasion by non-native species are major disturbances in this system. Both domestic animals and wildlife use this system readily, leading to trampling of vegetation and an increase in shrub and grass domination. Boxelder is highly susceptible to mechanical damage from livestock (Rosario 1988), and in stands where green ash is dominant, heavy livestock grazing may prevent regeneration, leading to more open stands dominated by exotic perennial grasses (Lesica 2009). A study in Green Ash dominated draws in the northern Great Plains found that exclusion of livestock increased tree height and decreased mortality for both Green Ash and Elm (Uresk et al. 2009).

Fire is an important process and may promote regeneration by encouraging sprouting and thinning of stands (Lesica 2003). Fire return intervals in these communities average approximately 30 years and range from low-severity surface fires to stand-replacing burns (U.S. Department of Agriculture 2012). Most community dominants are highly susceptible to fire, although Green Ash and Rocky Mountain Juniper may survive low-intensity burns in some cases (Gucker 2005; Scher 2002). Despite experiencing high mortality due to fire, species in this group are fire-adapted and recover quickly via root sprouting, as is the case with Aspen and Green Ash, or by prolific seed production and wind dispersal, as is the case with Paper Birch and Boxelder. Most species in this group, however, are capable of utilizing both strategies to varying degrees (Gucker 2005; Howard 1996; Uchytil 1991; Rosario 1988).

In parts of eastern Montana, non-native species like Russian Olive have invaded these communities altering vegetation composition and changing biogeochemical cycling in streams (Mineau et al. 2011). Russian Olive trees are fast-growing and form a dense canopy that prevents the more shade-intolerant native species typical of this system from establishing (Combs 2010). Additionally, Russian Olive exerts a strong competitive effect on native tree species in this system, inhibiting their establishment (Katz and Shafroth 2003). Non-native grasses also alter species composition within these communities, particularly where green ash is dominant, by forming dense sods and preventing seedling recruitment (Lesica 2009).

Shade and moisture draw livestock into draws and ravines, concentrating use and creating the potential for degradation and the spread of exotic and invasive species. Alternative areas of shade, water, and forage for livestock can reduce pressure on these communities and maintain them as wildlife habitat. Fire may have mixed effects on this system. In southeastern Montana, burning resulted in increased abundance and size of crown sprouts in Green Ash-dominated wooded draws, although significantly fewer seedlings were observed in burned sites (Lesica 2003). Prescribed burning may be beneficial to maintaining this system where regrowth will not be impeded by invasive grasses, intensive ungulate browsing, or where Russian Olive has not invaded (Lesica and Marlow 2011; Lesica 2009; Katz and Shafroth 2003).

Restoration of this system may in part require alternate grazing practices to allow for successful recovery. Dominant species such as Chokecherry, Hawthorne and Elm have extensive root systems and are rated as good to excellent for soil erosion control. Aspen and Paper Birch are additionally recommended for revegetation and soil stabilization (Howard 1996; Uchytil 1991). In some cases, shrubs can be planted in clusters or bands in areas with high soil erosion potential. All other associated understory shrubs within this system - Western Snowberry, Silverberry, Currants and Gooseberry, Woods' Rose, and Silver Buffaloberry - are rated as good to excellent restoration species, and possess strongly rhizomatous root systems that minimize soil erosion on steep slopes.

In order to promote regeneration in areas where green ash recruitment has been prevented by exotic grasses, Lesica (2009) recommends herbicide treatment followed by seeding. Alternatively, cutting of mature individuals encourages sprouting, which may be more successful than direct seeding. However, intensive browsing by ungulates may limit the success of this approach (Lesica 2009). In wooded draws where Russian Olive has become dominant, the most effective method of restoration employs a combination of chemical and mechanical treatments. Prescribed burning is not recommended as Russian Olive readily resprouts post-fire (Katz and Shafroth 2003). Combs (2010) recommends specific methods for reducing Russian Olive where invasion into this system has occurred.

J. Drake 2015

S. Mincemoyer, L. Vance, T. Luna

11/25/2024