Montana Field Guide

This group is a minor type that occurs in the valleys of southwest Montana and in the Bighorn Basin in Carbon County. These communities usually consist of open to moderately dense shrubs dominated by Black Greasewood (Sarcobatus vermiculatus) with a sparse graminoid understory. It is found on nearly level, older alluvial terraces on broad or narrow floodplains and alluvial fans in valley bottoms. It may also occur on broad expanses along lake shores and playas. Sites typically have saline soils and a shallow water table. They flood intermittently, but the surface is dry for most of the growing season. The water table remains high enough to maintain vegetation, despite salt accumulations. In many cases, fine textured soils result in a perched water table.

This Group encompasses the portion of the Greasewood Flat Ecological System that occurs in the Intermountain Basins of southwest MT and in the Bighorn Basin in south-central MT. Greasewood communities in the Great Plains Region are included in G566 (Great Plains Sparsely-Vegetated Badlands) or G984 (Great Plains Saline Wet Meadow & Marsh).

Alkaline and Saline Shrubland; Lowlands, Toeslope and Valley Bottoms, Deep Silt and Clay Soils, Intermountain and Bighorn Basin Regions

Typical Dominants: Black Greasewood (Sarcobatus vermiculatus)

This Group is a minor type that occurs in the valleys of southwest Montana and in the Bighorn Basin in Carbon County. Greasewood communities in the Great Plains Region are included in G566 (Great Plains Sparsely-Vegetated Badlands) or G984 (Great Plains Saline Wet Meadow & Marsh).

In Montana, G537 occurs in Level IV Ecoregions: 18b (Bighorn Basin), 43v (Pryor-Bighorn Foothills) and 17aa (Dry Intermontane Sagebrush Valleys).

In Montana, G537 occurs or potentially occurs within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins, 44B - Central Rocky Mountain Valleys, and the southern portion of 46 - Northern and Central Rocky Mountain Foothills

Small Patch and Large Patch

In Montana, this ecological system represents one of the driest extremes of the riparian/wetland zone. It occurs on nearly level, older alluvial terraces on broad or narrow floodplains and alluvial fans in valley bottoms. It may also occur on broad expanses along lake shores and playas. Sites typically have saline or alkaline soils and a shallow water table. They flood intermittently but remain dry for most of the growing season. However, the underlying water table stays high enough to maintain vegetation, despite salt accumulations. The system occurs where overland flow or soils or a combination of both allow for a greater than normal moisture regime. High water tables are common, typically within 10 to 12 inches of the soil surface. Soils are fine textured and range from silt to clay.

Black Greasewood (Sarcobatus vermiculatus) is the dominant shrub, although overall canopy cover may be low. Other shrubs present in some occurrences include Fourwing Saltbush (Atriplex canescens), Shadscale (Atriplex confertifolia), Gardner’s Saltbush (Atriplex gardneri), Wyoming Big Sagebrush (Artemisia tridentata ssp. wyomingensis), Basin Big Sagebrush (Artemisia tridentata ssp. tridentata), Silver Sage (Artemisia cana ssp. cana), Green Rabbitbrush (Chrysothamnus viscidiflorus), Rubber Rabbitbrush (Ericameria nauseosa) or Winterfat (Krascheninnikovia lanata).

Perennial grasses are the most common herbaceous cover, with Western Wheatgrass (Elymus smithii) tending to dominate in undisturbed communities. Other graminoids commonly occurring in this system include Slender Wheatgrass (Elymus trachycaulus), Nutall’s Alkaligrass (Puccinellia nuttalliana), Sandberg’s Bluegrass (Poa secunda), Inland Saltgrass (Distichlis spicata), Alkali Sacaton (Sporobolus airoides), Prairie Sandreed (Calamovilfa longifolia), and Basin Wildrye (Elymus cinereus). Common forb species include yarrow (Achillea millefolium), Goldenweed (Pyrrocoma uniflora), Fringed Sage (Artemisia frigida), Western Sagewort (Artemisia ludoviciana), Goosefoot (Chenopodium species), Scarlet Globemallow (Sphaeralcea coccinea), Western Saltwort (Salicornia rubra) and Curlycup Gumweed (Grindelia squarrosa).

Adjacent drier communities are dominated by upland shrub or grassland communities such as Salt Desert Scrub or Big Sagebrush (Artemisia tridentata) shrublands. Wetter adjacent communities may be dominated by Inland Saltgrass (Distichlis spicata) or willow-cottonwood (Salix-Populus species) dominated communities.

In Montana, this group is represented by 1 Alliance with 4 Associations within the National Vegetation Classification, which likely cover the diversity of types within this group. Black Greasewood communities within the Great Plains Region are part of either G566 - Great Plains Sparsely-Vegetated Badlands or G984 - Great Plains Saline Marsh & Wet Meadow.

Soil-water dynamics within these communities support a restricted range of species. Communities in good condition typically have 30 to 40 % shrub cover. Under continued disturbance, greasewood and western wheatgrass decrease in cover, while species such as foxtail barley (Hordeum jubatum) and yarrow (Achillea millefolium), and exotics like cheatgrass (Bromus tectorum), Japanese brome (Bromus japonicus) and Kentucky bluegrass (Poa pratensis), increase in cover.

Overgrazing practices can significantly impact vigor and cover of the principal shrub species, leading to an increase in cheatgrass and other exotics, although herbaceous cover in this system is often too low to attract cattle away from surrounding uplands. Off-road travel can be a disturbance, especially in the early season, when clayey soils are still soft. In any season, heavy off-road travel can be harmful to the very slow growing dominant shrub species.

In cases where the system has been impacted by heavy grazing, a rest-rotation regime with limited fall grazing may allow this system to recover by allowing regrowth of principal graminoid and shrub species. Severely impacted sites should be re-seeded to decrease soil erosion potential, to re-establish a native community, and to decrease weedy invasion by exotic species. Western Wheatgrass can be used as the principal restoration species and can be seeded or transplanted as plugs. Once established this species spreads vigorously by rhizomes. Both Greasewood and Western Wheatgrass exhibit excellent soil erosion control characteristics. Replanting with Greasewood seedlings may be necessary due to the slow recovery time within this system and low rates of natural seedling recruitment.

G. Kittel 2015

S. Mincemoyer, C. McIntyre, L. Vance, T. Luna

12/5/2024