State 1
Reference State

Community 1.1
Historic Climax Plant Community

Tall and medium height cool-season perennial grasses with less than or equal to 15 percent native shrubs. Bluebunch wheatgrass, western and thickspike wheatgrass, green needlegrass, little bluestem, and needle and thread are the most common grasses in this community. Bluebunch wheatgrass is more prevalent in the western portion, rather than the eastern portion of the Glaciated Plains. These tall and mid, cool season grasses account for 60-70 percent of the total production. Two warm season, short grasses (plains muhly and blue grama) and a mix of cool season short grasses (prairie junegrass, plains reedgrass, and sandberg bluegrass) commonly occur in the Historic Climax Plant Community (HCPC). Total production by short grasses usually represents less than 10% of the total production. Needle and thread, a mid-successional cool season bunchgrass, may produce from 10-20% of the total annual production. American vetch (cool season) and purple and white prairie clover (warm season) are native, nitrogen-fixing legumes. They are valuable forage plants and are also an integral part of the HCPC. Milkvetch and prairie thermopsis are two additional legumes that fix nitrogen. However, they are generally rated as fair and poor forage for livestock, respectively. Bastard toadflax, aster, and hoods phlox should be no more than a minor component of the forb community. Skunkbush sumac and winterfat, respectively, are important cool and warm season shrubs. They should be present in the HCPC. Shrubs such as creeping juniper, broom snakeweed, prickly pear cactus and fringed sagewort should be no more than a minor component of the community. Similarity indices >75% are associated with this community. Tall and mid cool season grasses generally dominate the HCPC. However, the Shallow 10-14” p.z. ecological site is not characterized by a precise assemblage of species that remains constant from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. For example, little bluestem and sideoats grama production is favored on north and east aspects, while bluebunch wheatgrass and needle and thread growth is favored on south and west aspects. Little bluestem and needle and thread also prefer coarse textured soils, rather than fine textured soils. The HCPC often regresses to lower seral stages. Regression may result from grazing management strategies that do not allow adequate recovery periods between grazing events, drought, and/or the disruption of the normal fire sequence. The above disturbances favor the replacement of little bluestem, bluebunch wheatgrass, western/thickspike wheatgrasses, and other deep-rooted, perennial grasses by blue grama, sandberg bluegrass, prairie junegrass, hairy goldenaster, hoods phlox and clubmoss. Winterfat, skunkbush sumac, and other desirable shrubs may also be replaced by broom snakeweed, fringed sagewort, etc. Cheatgrass and Japanese brome may colonize the site. As the result of these vegetative changes, there is less litter to protect the soil and less infiltration. Hydrologic cycles are impaired as plant communities are unable to effectively use precipitation. Plant cover (litter, and canopy of grasses, forbs and shrubs) is greater than 70% Therefore, plant cover and litter are adequate to optimize infiltration, minimize runoff and erosion, and provide good hydrologic conditions. Research and experience have not shown that excess litter adversely impacts ecological processes on the shallow 10-14” ecological site. The diverse mix of species found at HCPC help warm and cool season grasses, forbs, and shrubs ensures that the soil profile contains an adequate mix of deep and shallow roots to maintain or increase infiltration rates and reduce runoff. Runoff and soil erosion normally increase as the HCPC regresses to earlier seral states. However, the ecological role of fire on Shallow sites is not fully understood. Fires would presence of clubmoss cover may reduce runoff and soil erosion on some soils. Clubmoss is also very competitive. Once it forms a mat, observations and experience along Montana’s Highline indicate that plant succession and site resiliency are adversely impacted. Most ecologists recognize that significant managerial changes are needed before a clubmoss community can return to HCPC. The HCPC is believed to have evolved with periodic fires occurring at intervals of 10-12 years. Fires temporarily reduce litter and favor, thus allowing more runoff. However, fire favors the succession of grasses and forbs at the expense of half-shrubs and shrubs. It is believed that frequent fires would have reduced clubmoss. As fire frequency decreased with the establishment of ranches and farms, clubmoss and the woody component of some communities may have increased. Where fuel loads increased above historic levels, today’s fires may burn hotter and increase the potential for accelerated wind and water erosion.

Community 1.2
Plant Community A Lower Production; plant hight shift

Medium height cool-season perennial grasses with less than or equal to 15 percent native shrubs (increase in some Artemisia species). Plant Community A is characterized by a mix of tall, mid and short grasses and sedges. Range inventories conducted by NRCS on the Fort Peck and Belknap Reservations indicate similarity indices of 55-75 are indicative of this community. The lower-stature plants tend to produce less forage than the mid grasses that they replaced. In contrast to the HCPC, total vegetation production may be 10-20% lower in Community A. In comparison to the HCPC, the amount of needle and thread grass has increased, while western or thickspike wheatgrass decreased. Blue grama and threadleaf sedge increased and are more common in the community. The total percentage of warm season, lower successional species (hairy goldenaster, scurfpeas, hoods phlox, and aster) has increased. Although some of the native shrubs decline in vigor and abundance, fringed sagewort and silver sagebrush often increase. Thus the total shrub component may be greater than 15%. Effects of grazing management and/or climatic conditions are visible. Preferred forage species are grazed and/or stunted, canopy cover is reduced, litter is reduced, and bare ground is increased. In comparison to the HCPC, this community is slightly drier. Thus, species such as blue grama, prairie junegrass and some increaser forbs have gained a competitive advantage over the tall, cool-season, deep-rooted perennial grasses. The short grasses are able to compete more successfully with the tall grasses because of the ability of relatively shallow root systems to utilize shallowly penetrating moisture, characteristic of drier habitats (Coupland, 1961).

Community 1.3
Plant Community B Pre-threshold Community

Medium and short height cool- and warm-season perennial grasses, increase of native forbs, and greater than 15 percent native shrubs. Plant Community B is dominated by a mix of medium and short grasses. In comparison to Community A, the short grasses contain more blue grama, a warm season species. The number of warm season forbs, such as hairy goldenaster, aster, and western yarrow increase and replace the prairie clovers, American vetch, and black Sampson. The warm season half-shrub, fringed sagewort, also increases. Thus, this community is characterized by a functional shift from a cool season dominant to more warm season species. Litter varies from 10-15%. In contrast to the HCPC, there is about 1/3 more bare ground. Rills, flow patterns and litter deposits are visible. Similarity indices of 45-55 characterize this plant community. Blue grama, threadleaf sedge, needleandthread and clubmoss have increased in the community by replacing some of the mid grasses. Total annual production normally varies from 500-600 lbs/ac. Plant community B is called the “pre-threshold community”. It is a critical that this community be recognized and strategies implemented to prevent further regression. Although this community can improve to either Community A or HCPC through successional processes, further disturbance will result in regression to a lower state. Once Community B regresses to a lower state, normal successional processes are usually restricted.

Pathway 1.1A
Community 1.1 to 1.2

No fire, non-prescribed grazing, and drought (3 to 5 years) Non-prescribed grazing, drought and/or a cessation of fire will cause regression from HCPC to Community A.

Pathway 1.2A
Community 1.2 to 1.1

Fire, prescribed grazing Succession from Plant Community A to HCPC occur fairly readily, and usually result from either planned grazing management, reintroduction of the natural fire regime, and/or periods of favorable precipitation. This succession can occur within a few years.

Pathway 1.2B
Community 1.2 to 1.3

No fire, non-prescribed grazing, prolonged drought (5 to 7 years) Community A will regress to Community B under non-prescribed grazing, prolonged drought, of an extended period of no fire. The rate of regression varies with the intensity of the disturbances. Severe drought may cause retrogression within a couple years.

Pathway 1.3A
Community 1.3 to 1.2

Fire, prescribed grazing, favorable precipitation This varies with environmental conditions. Generally, as the percentage of warm season short grasses and warm season forbs increase above 35%, succession to Plant Community A and eventually HCPC become slower and are less likely to occur. Succession is more likely to occur with prolonged periods of favorable rainfall combined with prescribed grazing. A reintroduction of the natural fire regime may also aid in shifting Plant Community B back to Plant Community A or the HCPC.

State 2
Degraded State

Plant Community C

Community 2.1
Short Grasses/Invaded

Plant Community C Blue grama, threadleaf sedge and clubmoss dominate the community. The group of short, warm season grasses and sedges produce nearly ½ of the vegetation. Prickly pear cactus and annual grasses have also increased. Western or thickspike wheatgrass and bluebunch wheatgrass occur as scattered plants or remnants. Needleandthread declined in vigor and it has been supplanted by lower-successional grasses and forbs. Similarity indices vary from 0 to 35 percent. Total annual vegetation production averages about 300 lbs. Litter cover declines to 15-20%. However, the decline in litter is partially offset by an increase in clubmoss cover (often exceeding 20%). Initial runoff rates from clubmoss-covered soils are reduced compared to bare ground, but may increase as the clubmoss becomes saturated. Because of the steep slopes and shallow soils, soil erosion is a major resource concern.

Transition T1A
State 1 to 2

Extended drought (greater than 7 years), non-prescribed grazing, no fire Transitions from State 1 (Plant Community B) to State 2 occur under prolonged, heavy continuous grazing. Prolonged drought exacerbates the retrogression, and lack of the natural fire regime also facilitates the transition.

Restoration pathway R2A
State 2 to 1

Prescribed grazing with favorable precipitation, fire if enough fuel. This plant community (State 2) is resistant to change. Blue grama and clubmoss form a thick sod which provides a competitive advantage for limited precipitation. Although the sod appears to prevent seedling establishment of high-successional species, recent research indicates the absence of seedlings within a mat of clubmoss is due to an inadequate seed bank in the soil (Romo and Bai 2004). When clubmoss cover is more than 20-25%, succession is not expected to occur within a reasonable length of time. However, significant succession may occur if the top soil is intact and if clubmoss is no more than a minor component of the plant community. Succession would be favored by prescribed grazing, an extended period of favorable precipitation and the re-implementation of the natural fire regime. The potential for succession is depicted by the dashed line in the diagram. Significant economic inputs and time are required to move this plant community toward a higher successional state (those communities found in State #1) when the plant community is dominated by clubmoss, or if the soil surface has been lost to erosion. Production on a Shallow 10-14” p.z. ecological site is 40-50% less than it is on ecological sites with soils > 20 inches deep (eg, Silty 10-14” p.z., Clayey 10-14” p.z., and Sandy 10-14” p.z.). The lower response potential from mechanical treatment has a proportionate effect on the potential economic benefits. Therefore, mechanical treatments and range seeding are not normally recommended on shallow sites. In comparison to “normal” sites, environmental risks (such as erosion) are greater while economic benefits are less.