State 1
Reference State

Community 1.1
Historic Climax Plant Community (HCPC) Tall- and medium-height cool-season perennial grasses with less than or equal to 5 percent native perennial forbs and less than or equal to 10 percent native shrubs

Tall- and medium-height cool-season perennial grasses with less than or equal to 5 percent native perennial forbs and less than or equal to 10 percent native shrubs The interpretive plant community for this site is the Historic Climax Plant Community (HCPC). Cool season tall and mid-grasses (such as bluebunch wheatgrass, green needlegrass, western wheatgrass, thickspike wheatgrass, porcupine grass and needle and thread) dominate the HCPC. These cool season grasses represent about 75% of the total annual plant production in the community. Bluebunch wheatgrass is the dominant bunchgrass on Silty-Steep sites in the northern Glaciated plains. Less common species in the HCPC include short grasses and sedges (plains muhly, prairie junegrass, threadleaf sedge, plains reedgrass and blue grama). These short grasses and grasslike plants contribute about 10% of the annual production. Dotted gayfeather, scurfpeas, and prairie clovers are important warm season forbs. American vetch may be the most important cool season forb. In addition to being desirable forage, it also fixes nitrogen. Total forb production normally represents less than 5% of the total annual production. Winterfat is a common warm season shrub that is highly prized as browse for livestock and wildlife. Rose and snowberry, two cool season shrubs often are present on the site. Silver sagebrush and fringed sagewort, two warm season shrubs may also be found on the site. Overall, shrubs account for about 10% of the annual plant production. Annual production of the Historic Climax Plant Community (HCPC) on Silty-Steep 10-14” p.z. ecological sites in the Glaciated Plains is not fully documented by either range inventory data collected (in 2001 and 2004) on the Fort Peck or Fort Belknap Indian Reservations, or with soil-vegetation correlation data (NRCS-417 Forms) in Northeastern Montana. Inventory data indicates that Similarity indices (SI) of 55-75% were associated with annual production estimates of 925 lbs/ac. Thus, 1200 lb/ac is accepted as a reasonable average production estimate for the HCPC, as inventoried and reported in the August 1981 range site description. Average annual production is expected to increase and decrease, respectively on more mesic and xeric portions of the northern Glaciated plains. The HCPC is well adapted to the Glaciated Plains. Precipitation is the most important factor influencing production (Heitschmidt et al 2005). The functional and structural diversity of plant species (annuals, perennials, cool and warm season grasses, forbs and shrubs) optimize the capture of solar energy and maximize subsequent plant growth through the efficient use of available soil water and nutrient cycling. When disturbances reduce the competitiveness of tall cool season grasses of the HCPC, warm season perennial forbs (hairy golden aster, scurfpea), annual forbs (wooly plantain, etc.) half-shrubs (fringed sagewort, etc.) and annual bromes often invade the community. The HCPC is resilient. With proper grazing management and non-drought conditions, the species characteristic of the HCPC will replace these lower successional species within a few years. Litter is in contact with 50-60% of the soil surface. About 10% of the soil surface is bare ground (i.e., unprotected by litter, rock, moss, and plant canopy). Because of the slope, vegetation and soils, rills, water flow patterns, and some movement of litter are noticeable following a rainfall event. The major plant species composition and production by dry weight are shown for the HCPC in the following table. Total annual production has been derived from several sources, and has been adjusted to represent a typical annual precipitation cycle.

Community 1.2
Plant Community A Shift in species composition, lower production, medium- and tall-height cool-season perennial grasses, about 5 percent native perennial forbs, and 10 percent native shrubs

Shift in species composition, lower production, medium- and tall-height cool-season perennial grasses, about 5 percent native perennial forbs, and 10 percent native shrubs Total plant production averages about 1,000 lbs/ac in this Plant Community, or about 80% of the production in the HCPC. The decrease in production results from a shift in species composition. Needle and thread, threadleaf sedge, blue grama and plains reedgrasss increased at the expense of the tall, more palatable grasses (bluebunch wheatgrass, green needlegrass, and western/thickspike wheatgrasses). In comparison to the HCPC, production of blue grama, prairie junegrass, plains reedgrass, threadleaf sedge and other short grasses increased. They now account for about 20% of the total annual production. Exact response by these species varies with the kind of disturbance (drought, grazing, etc.) and with precipitation (amount and timing). Total production of native forbs remains at about 5% of annual production of the site. However, the palatable species (prairie clovers, American vetch and dotted gayfeather) decrease in abundance (relative to the HCPC). The open niches allow hairy goldenaster, bastard toadflax, prairie thermopsis, etc. to become more abundant. Shrubs continue to account for about 10% of the total production. However, species such as fringed sagewort and silver sagebrush increase (relative to the HCPC). Similarity index values from 55-75% are associated with this community. In contrast to the HCPC, range conservationists have moderate concerns regarding lower successional plants, lower infiltration rates and potentially higher runoff rates, plant functional/structural group shifts, and decreasing amount of litter.

Community 1.3
Plant Community B - Pre-threshold Community Medium- and short-height cool- and warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present

Medium- and short-height cool- and warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present Plant Community B is dominated by needle and thread, blue grama, plains reedgrass, prairie junegrass and upland sedges. However, individual plants of bluebunch wheatgrass, green needlegrass, and western/thickspike wheatgrass remain in the Community. The short grass and grass-like plants make up about 30% of the total production. Total vegetative production declines to about 800 lbs/ac in a normal year. Hairy goldenaster, scarlet globemallow, scurfpeas and other warm season forbs increase at the expense of the prairie clovers and American vetch. Forbs account for about 10% total annual production. Fringed sagewort, a half-shrub increases at the expense of winterfat. Silver sagebrush and rose also increase on some sites. Shrubs account for about 15% of the total plant production. SI values for this community vary from 35-55%. Litter provides cover for about 30% of the ground, while bare ground increases to about 25%. Rills, water flow patterns and litter movement are evident on the site. The tall cool season grasses have poor vigor, with little seed production. Most of the seedlings and young plants appear to represent short grasses and warm season forbs. Lower successional plant species and some invasive species are a significant part of the community. Japanese brome and cheatgrass are usually present wherever rodents or other disturbances create an open niche. Plant Community B is fairly resilient, but it is not highly resistant to disturbance. It is the “pre-threshold” community. Therefore, it is critical that this community be recognized and strategies implemented to prevent further regression. Community B can readily regress to a lower state, from which succession back to the HCPC community or Plant Community A would be restricted.

Pathway 1.1A
Community 1.1 to 1.2

No fire, non-prescribed grazing, drought (3 to 5 years) Successional pathways from the HCPC are influenced by frequency, timing and intensity of grazing, precipitation patterns, fire, insect infestations, noxious weed colonization and recruitment, etc. As communities regress from HCPC, medium and short grasses increase at the expense of mid and tall cool season grasses. The medium and short grasses consist of cool (prairie junegrass, upland sedges, and sandberg bluegrass) and warm season grasses (blue grama and plains reedgrass) and grasslike plants.

Pathway 1.2A
Community 1.2 to 1.1

Fire (natural interval 5 to 7 years), prescribed grazing, normal precipitation Plant Community A is resilient. Successional processes can readily return Plant Community A to the HCPC during normal precipitation cycles. Succession is facilitated by prescribed grazing, the incorporation of the natural fire regime into the system, etc.

Pathway 1.2B
Community 1.2 to 1.3

No fire, prescribed grazing, prolonged drought (5 to 7 years) Plant community A is resistant. However, prolonged drought, non-prescribed grazing, and the removal of fire from the system will result in retrogression to Community B. The causative factors of regression are usually apparent with careful observation.

Pathway 1.3A
Community 1.3 to 1.2

Fire (natural interval 5 to 7 years), prescribed grazing, favorable precipitation Favorable precipitation and prescribed grazing are normally required for succession to higher successional communities (Community A or HCPC). Management strategies should focus on grazing deferment to increase vigor and seed production of desirable plants, and to increase litter cover. Increasing litter is extremely critical because of the steep slopes.

State 2
Degraded State

Community 2.1
Plant Community C Short, warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present

Short, warm-season perennial grasses, annual forbs, clubmoss, and shrubs greater than 20 percent, invasive species present State 2 Plant Community C is dominated by blue grama, prairie junegrass, sandberg bluegrass, prairie sandreed, other short grasses, and clubmoss. However, a few individual western wheatgrass, bluebunch wheatgrass, etc. plants seem to persist longer than they do on surrounding ecological sites. The ability of these palatable plants to persist on the Silty-Steep 10-14” p.z site is probably a reflection of lighter grazing use. Cattle prefer grazing areas with less than 15% slope, and those areas adjacent to livestock water developments. Red threeawn, Japanese brome and cheatgrass often invade this Community. Wooly plantain, hoods phlox, hairy goldenaster and bastard toadflax are common forbs. Fringed sagewort usually increases. Silver sagebrush and rose may also increase. The most palatable shrubs are nearly absent. SI values of less than 25% are associated with State 2. Surface runoff and soil erosion are a serious concern on the Silty-Steep 10-14” p.z. site. The decrease in plant cover and litter increases the susceptibility to erosion. Less vegetative growth is available for transfer to litter, and nutrient cycling is delayed or impeded. As bare ground increases, infiltration decreases and/or surface runoff and soil evaporation increases. Because ecological processes of the site are no longer balanced and sustained, shallow rooted, warm season species continue to gain a competitive advantage over the deep rooted, cool season species. The biotic integrity of the site is degraded. In comparison to the State 1 communities, State 2 is less efficient in capturing solar energy and converting it to carbohydrates for plant growth. Total vegetative production averages about 400 lbs/ac. The absence of tall and mid cool season perennial grasses, plus the shift from cool season plants to warm season plants, indicates that the structural and functional processes of this site have been disrupted. However, if the soil surface is stable and does not erode, site potential may not be significantly impaired.

Transition T1A
State 1 to 2

Extended drought (greater than 7 years), non-prescribed grazing, no fire Plant Community B will regress to a lower state with any combination of extended drought, non-prescribed grazing and unfavorable climatic patterns. This transition from Community B to State 2 represents a threshold, or a point in space and time at which one or more of the primary ecological processes responsible for maintaining the sustained equilibrium of the state degrades beyond the point of self-repair.

Restoration pathway R2A
State 2 to 1

Prescribed grazing, fire (natural interval 5 to 7 years), extended favorable precipitation Plant community succession across a threshold to a higher state is ecologically difficult in most ecosystems. A significant input of energy is often required for succession to occur. In instances of prolonged favorable climatic conditions combined with proper management, the significant input of energy that is normally required to move this site across the threshold (from State 2 to State 1) may not be needed. Because of the steep slopes, mechanical treatments and range seeding are not recommended. Ranchers should be aware of the limitations of this site. Rather than trying to change nature, managers must learn to live within the environmental boundaries of this site. Prescribed grazing management should be a requirement for this site.