INTEGRATED NATURAL RESOURCES MANAGEMENT PLAN
Page 30 of 165
2.3 Ecosystems and the Biotic Environment
2.3.1 Ecosystem Classification
The Hierarchical Framework of Ecological Units is a classification and mapping process that recognizes
functional resource areas with similar management possibilities, based on patterns in soil types, natural
communities, hydrologic function, topography, climate, and other natural processes such as nutrient
cycling, successional processes, and natural disturbance regimes associated with flooding, wind, or fire
(Cleland et al., 1997). Areas that share common classifications can be combined into ecological units or
ecoregions that share regional climatic regimes, habitats, and gross physiography (Cleland et al., 1997).
Ecoregions denote areas of general ecosystem similarity in type, quality, and quantity of environmental
resources (Woods et al., 2002). Ecoregion Levels adapted from Bailey (1980) and compiled by Bailey
(1995) range from coarse to fine resolution. Malmstrom AFB and the deployment area can be described
in context of Domains, Divisions, and/or Provinces based on scale. The coarsest regional classification
for the Base and deployment area is the Domain, followed by Divisions, with Provinces a finer scale.
According to classification methods by Baily (1995) Malmstrom AFB is found in the Dry Domain. The
Dry Domain covers approximately half of the continental United States (west of the Mississippi River to
the Rocky Mountains). An area where annual evaporation rates exceed annual precipitation rates
characterize this domain. The Dry Domain is subdivided into five Divisions, which in turn is divided into
14 provinces. Based on this classification system (Baily, 1995), Malmstrom AFB and the deployment
area fall within the Temperate Steppe Division and the Great Plains-Palouse Dry Steppe Province. The
State of Montana has been divided into Level III and Level IV ecoregions (Woods et al., 2002).
The US Environmental Protection Agency (EPA, 2013) developed a higher resolution effort for defining
ecoregions, incorporating the data from (Woods et al. 2002). According to this categorization system, the
Base and deployment area fall within the Northwestern Glaciated Plains, Northwestern Great Plains, and
Middle Rockies Level III ecoregions (EPA, 2013). Figure 8, illustrates the location of Malmstrom AFB
in relation to other surrounding ecoregions. Regardless of nomenclature, i.e. Temperate Steppe Division
(Baily, 1995), Northwestern Glaciated Plains, Northwestern Great Plains, etc. (EPA, 2013), Malmstrom
AFB and the deployment area is a semiarid climatic regime where evaporation usually exceeds
precipitation with cold, dry winters and hot summers. The predominant vegetation is characterized by
shortgrass prairie, with occasional shrubs and trees locally common (Baily, 1995).
Additionally, according to Baily (1995) this ecoregion is characterized by grasslands dominated by
Bluebunch wheatgrass, Fescue (genus Festuca), and Buffalograss (Bouteloua dactyloides). Historically,
large herds of American bison (Bison bison), seasonally migrated through this ecoregion and prairie dogs
(genus Cynomys), ground squirrels (family Sciuridae), and other small rodents where abundant and once
served as forage for Coyote (Canis latrans) and several other predators, including the Black-footed ferret
(Mustela nigripes) and various raptors. Today the Pronghorn antelope (Antilocapra americana) is the
most abundant large mammal, although Mule deer (Odocoileus hemionus) and Whitetail deer (Odocoileus
virginianus) are common where brush cover is found, and the Black-footed ferret is listed as a federally
endangered species (32 FR 4001) but no longer is present at Malmstrom AFB or in the deployment area.
While the ecoregion names may vary slightly depending on system of classification used, the underlying
generalities of habitat types, soils, precipitation, species assemblages, etc., are critical for structuring and
implementing ecosystem management strategies across federal agencies, state agencies, and
nongovernmental organizations that are responsible for different types of resources within the same
geographical areas (Woods et al., 2002; EPA, 2013).