State 1
State #1: Historic Climax Plant Community (HCPC)

Community 1.1
State #1: Historic Climax Plant Community (HCPC)

The interpretive plant community for this site is the Historic Climax Plant Community (HCPC). Cool season tall and mid-grasses (such as green needlegrass, western wheatgrass, thickspike wheatgrass, slender or bearded wheatgrass, basin wildrye and needleandthread grass) dominate the HCPC. These cool season grasses represent about 70% of the total annual plant production in the community. Warm and cool season short grasses and sedges (prairie junegrass, upland sedges, plains reed grass and blue grama) make up 10% of the total annual production. Goldenrods, scurfpeas, maximilian sunflower, cudweed sagewort, and western yarrow are important warm season forbs. American vetch, cinquefoil and penstemon are common cool season forbs. American vetch, milk vetch, prairie thermopsis, and scurfpea are important nitrogenous-fixing legumes. Total forb production normally represents less than 10% of the total annual production. Western snowberry, prairie rose, buffalo berry and chokecherry are common cool season shrubs. Silver sagebrush and fringed sagewort are common warm season shrubs. Overall, shrubs account for about 10% of the annual plant production. Annual production averages 2500 lbs/ac during “normal” years. Range inventory data collected (in 2001 and 2004) on the Fort Peck and Fort Belknap Indian Reservations indicate total above ground production averaged 2132 lbs/ac in plant communities associated with similarity indices of 45-65. Therefore, the 2500 lb/ac estimate is reasonable for the HCPC. Annual production is expected to increase and decrease, respectively on more mesic and xeric portions of the Glaciated plains. This plant community is well adapted to the Glaciated plains. Precipitation and run-in water are the most important factors influencing production. 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. Continued adverse disturbances reduce the competitiveness of perennial plants, and precipitate the replacement of high successional species with lower successional grasses, forbs, shrubs, and annual species. With proper grazing management and non-drought conditions, more species found at HCPC will replace these lower successional species within a few years. Litter is in contact with 60% of the soil surface. Plant litter remains in place and is not moved by erosional forces. Plant basal canopy cover averages 40%. Less than 1% of the soil surface should be bare, or unprotected by litter, rock, moss, and plant canopy. Rills should not be present and water flow patterns should be barely observable.

Community 1.2
Plant Community A (State #1)

*Successional pathway from HCPC to Community A (State #1): 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 warm season grasses increase at the expense of mid and tall cool season grasses. Plant Community A (State #1): Total plant production averages about 1700 lbs/ac in this Plant Community. The tall, cool season grasses (green needlegrass, basin wildrye, switchgrass, big bluestem, and prairie cordgrass) persist in the community but have lost vigor with little evidence of successful regeneration. Western wheatgrass, prairie junegrass, blue grama and needleandthread grass have increased and contribute about 40% of the total annual production. Exact response of western wheatgrass and these lower successional species vary with the kind of disturbance (drought, grazing, etc.) and with precipitation (amount and timing). Production of native forbs increases relative to the HCPC and now accounts for more than 10% of the total production. Dotted gayfeather and American vetch tend to be replaced by cudweed sagewort, hoods phlox, etc. Shrubs account for about 15% of the total annual production. Species such as snowberry, fringed sagewort and silver sagebrush increase at the expense of chokecherry, golden currant and American plum. SI indicies from 35-65% are associated with this community. Litter cover decreases to 50% and bare ground increases to 5 – 10 %. In contrast to the HCPC, range conservationists have slight to moderate concerns regarding lower infiltration rates and potentially higher runoff rates, plant functional/structural group shifts, decreasing amount of litter, and increased presence of lower successional plants. 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. Plant Community A is not highly resistant to disturbance. It can readily regress to a lower state from which upward succession is restricted. Because it is the “pre-threshold” community, it is critical that this community be recognized and strategies implemented to prevent further regression (UDSA and USDI, 2000). *Successional Pathway from Community A to HCPC: Successional processes can readily return Plant Community A to the HCPC. The process can be facilitated by prescribed grazing, the incorporation of the natural fire regime into the system, etc. *Transition from State #1 to Communities B (State #2) and C (State #3): Prolonged drought, non-prescribed grazing, and the removal of fire in the system will result in retrogression to State #2. The effects of drought and poor grazing management are readily apparent with careful observation. However, the influence of fire is more difficult to verify. Because of the continual interaction of these environmental factors, regression from State #1 may culminate in two distinct communities (Community B or C). Community B is dominated by snowberry, fringed sagewort, and silver sagebrush. Community C is comprised of mostly short grasses, Kentucky bluegrass and low successional forbs.

State 2
Plant Community B (State #2)

Community 2.1
Plant Community B (State #2)

Native shrubs such as snowberry, silver sagebrush, fringed sagewort, and prairie rose account for 25% or more of total annual production. A few western wheatgrass and green needlegrass plants persist with low vigor in the community. Needleandthread, blue grama, prairie junegrass, sandberg bluegrass and upland sedges dominate the graminoids, and represent about 30% of the total annual production. Cinquefoil, prairie thermopsis, scurfpeas, western yarrow, cudweed sagewort, and other native low successional forbs make up about 20% of the total annual production. Dandelions, salsify, cocklebur, hounds tongue, Canada thistle, and other noxious forbs are usually conspicuous in the community. SI indices for this community vary from 1-34%. Total vegetative production declines to about 900 lbs/ac in a normal precipitation year. Litter provides cover for about 15% of the ground, while bare ground increases to about 25%. Rills, water flow patterns and litter movement are evident on the site.

State 3
Plant Community C (State #3)

Community 3.1
Plant Community C (State #3)

Plant Community C (State #3) is dominated by Kentucky and Canada bluegrass, blue grama, prairie junegrass, sandberg bluegrass, and needleandthread. Allthough some western wheatgrass persists as single shoots with few seedstalks, it is difficult to find green needlegrass or any other high successional grass that dominated the HCPC. Japanese brome and cheatgrass often colonize disturbed sites (rodent mounds, etc.) in this community. Wooly plantain, hoods phlox, hairy goldenaster and western yarrow are common forbs. These low successional forbs contribute about 20% of the annual production. Fringed sagewort usually increases while snowberry and silver sagebrush decrease in abundance. There are very few seedlings of desirable species. SI indices of 0-34% are associated with Community C. Soil erosion is not a serious problem because of the cover provided by the introduced rhizomatous and short native warm and cool season grasses. However, the loss of the tall cool season bunchgrasses results in a simplification of the compositional and structural plant communities. The hydrologic cycle (capture, storage and redistribution of precipitation), energy flow, and nutrient cycles are believed to be adversely impacted. Total vegetative production averages about 800 lbs/ac. In contrast to the reference state, range conservationists express moderate to extreme concerns about plant community composition, functional/structural groups, litter, annual production, and noxious plants. Each of the primary processes: 1) hydrology (the capture, storage and redistribution of precipitation), 2) energy capture (conversion of sunlight to plant and animal matter), and 3) nutrient cycling (the cycle of nutrients through the physical and biotic components of the environment) has been degraded beyond the point of self-repair within a reasonable length of time. For example, when tall, high producing, cool season grasses are replaced by short grasses (Kentucky bluegrass, blue grama, and prairie junegrass), the ability of the plant community to maximize the conversion of solar energy to plant biomass and efficiently utilize available precipitation are impaired. Less solar energy is captured and converted to carbohydrates for plant growth. Plant growth declines, and there is less plant canopy and less litter to protect the soil. 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 compromised. *Successional Pathways between Communities B & C: Plant communities B & C are not a precise assemblage of species that remain constant from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. However, dominant status is less variable. Changes in climate, fire patterns and frequency, and grazing all play a role in determining which of the plant communities will be expressed. Plant Community B regresses to Community C with non-prescribed grazing and/or a wildfire that removes the dominant shrubs from the community. The shift from Community C to Community B might occur with a combination of a natural fire regime, prescribed grazing and an extended period of favorable precipitation. The possibility of this succession is depicted with a dashed arrow in the state and transition diagram. *Transition from Community B (State #2) to State #1: The implementation of prescribed grazing and a favorable precipitation pattern normally will not induce succession from State #2 to State #1. Succession normally requires significant economic inputs. However, the Overflow 10-14” p.z. ecological site is productive. It is theorized that succession from Community B to State #1 may occur with the combination of a natural fire regime, prescribed grazing, and an extended period of favorable precipitation. This potential is depicted as a dashed arrow in the state and transition model. The Overflow 10-14” p.z. is a productive site with deep soils on landscapes with less than 2% slope. Although the potential of using mechanical treatments to promote plant succession is limited because this site often occurs as small and irregularly shaped tracts, mechanical treatments are feasible in some places (See NRCS Conservation Practice 548). Following mechanical treatment, it is critical that grazing is deferred one or two growing seasons. Length of grazing deferment varies with precipitation and response of vegetation. Furthermore, prescribed grazing must be implemented following the deferment. Failure to do will result in economic losses and potential ecological damage to the site. With prescribed grazing and plant succession, the effective life of treatment should be greater than 10 years. Prescribed burning may be a useful tool for promoting succession in the State #2 Plant Communities. Fire would reduce the shrubs in Community B, and also adversely impact the shallow-rooted Kentucky and Canada bluegrasses in Community C. The opening of the community will favor the establishment of new plants, if seed (and/or rhizomes) of desired plants are available. If not, range seeding may be necessary following mechanical treatment or fire.