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 10% native forbs and less than or equal to 5% native shrubs, basal cover equals 20% plant, 55% litter, and 15% bare ground

Tall and medium-height cool-season perennial grasses, with less than or equal to 10% native forbs and less than or equal to 5% native shrubs, basal cover equals 20% plant, 55% litter, and 15% bare ground Three cool season perennial grasses (western wheatgrass, thickspike wheatgrass and bluebunch wheatgrass) are the dominant plants in this community. They account for about 75% of the total annual production in the HCPC. One high-successional warm season short grass (plains muhly) commonly occurs in the HCPC communities, while the distribution of a second species (little bluestem) is restricted to the central glaciated plains (RRU 52XC). Drought and non-prescribed grazing reduces the competitiveness of the dominant species, and allows lower successional grasses (plains reedgrass, prairie junegrass, needleandthread, sandberg bluegrass, and blue grama) to increase on the site. Although it is a fairly palatable cool season grass, needle and thread is well-adapted to the droughty conditions of this site, and acts as an indicator species. Needle and thread contribution to total annual production varies from < 5% in the HCPC to > 30% in the early seral state. About 10% of the total production is made by a mix of warm and cool season short grasses and sedges. Forbs contribute about 10% of the total annual production. Two warm season legumes (purple and white prairie clover) and a cool season legume (American vetch) are important components of the HCPC. They fix nitrogen, and are highly palatable forage for livestock and many species of wildlife. Scurfpea is another warm season legume that fixes nitrogen, but it is not a desirable forage plant. Dotted gayfeather is another high-successional warm season species that occurs in the HCPC communities. Stemless hymenoxys, scarlet globemallow, white milkwort, hairy goldenaster, prairie coneflower, many-flowered aster, green sagewort, hoods phlox and biscuitroot may occur in the HCPC, but should contribute no more than a few pounds of annual production per acre. The latter group contains a mix of warm and cool season species whose relative occurrence on the site is largely influenced by the timing and amount of precipitation. Creeping juniper, yucca, silver sagebrush and fringed sagewort are common shrubs. Although these species have some value as browse for deer and antelope, they are highly valued as forage. Pricklypear cactus and brittle cactus may occur as a trace or very small components of the total community. Shrubs normally make up about 5% of the total annual production. Dense clubmoss, often occurs as a minor component in the HCPC. However, it often increases when the plant community is stressed by drought or other environmental factors. Although it is difficult to explain the density of clubmoss in specific communities, some soil scientists believe that heavy infestations of dense clubmoss are associated with the presence of an argillic layer in the soil. Broom snakeweed, annual bromes, and annual forbs are not a part of the HCPC. Their presence indicates possible ecological deterioration or downward trend. Total annual production averages 1000 lbs/ac during normal years. However, production declines as the site regresses from the HCPC to lower successional communities. 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 regime. The above disturbances favor the replacement of bluebunch wheatgrass, plains muhly, thickspike wheatgrass and western wheatgrass by lower successional species (blue grama, sandberg bluegrass, prairie junegrass, scarlet globemallow, etc.). Young fringed sagewort plants become more apparent as range health declines. Cheatgrass and Japanese brome may invade the site. As the result of these vegetative changes, there is less litter to protect the soil and less infiltration. Hydrologic cycles are impaired when plant communities are unable to effectively use precipitation. Plant basal cover averages about 20%, while litter varies from 50-60%. Bare ground averages 15%. Although runoff and erosion are not major concerns in the HCPC, they are increasing concerns as the HCPC regresses to earlier seral states. 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 moisture cycle.

Resilience management. The HCPC is comprised of a mixture of cool and warm season grasses, forbs and shrubs. About 85% of the annual production is from grasses and sedges, most of which is produced during the cool season. Forbs and shrubs contribute 10% and 5%, respectively, to total annual production. Total vegetative production averages 1000 lbs/ac in normal years, 700 lbs/ac in “unfavorable” years, and 1200 lbs/ac in “favorable” years.

Community 1.2
Plant Community A Lower production with reduction of plant height, medium-height cool-season perennial grasses, diverse mix of warm and cool-season short grasses, remnants of tall grasses, native shrubs equal to or greater than 10%, more bare ground

Lower production with reduction of plant height, medium-height cool-season perennial grasses, diverse mix of warm and cool-season short grasses, remnants of tall grasses, native shrubs equal to or greater than 10%, more bare ground Non-prescribed grazing and drought reduce plant height and plant litter. Total annual production is about 80% of production in the HCPC. Surface runoff and soil temperature increases, and infiltration decreases. Shallow-rooted short grasses (sandberg bluegrass, blue grama, and prairie junegrass) and sedges gain a competitive advantage over medium height, deep-rooted perennial grasses (bluebunch wheatgrass, thickspike wheatgrass and western wheatgrass). They are able to compete more successfully with the mid-grasses because of the ability of relatively shallow root systems to utilize shallowly penetrating moisture. Western wheatgrass, bluebunch wheatgrass, and thickspike wheatgrass contribute from 40-50% of the total annual production. Vigor of these high successional grasses declined, and individual plant growth is reduced from what it is in the HCPC. Production of the short grasses increases to about 35% of total annual production. Forb production increases (> 15% of total annual production) significantly above production in the HCPC. Fringed sagewort increased, but total shrub production remains at about 5% of total annual production. Plant community A is called the “pre-threshold community”. It is critical that this community be recognized. Range inventory data collected by the NRCS on Fort Peck and Fort Belknap Reservations from 2001-2004 indicate that this community is characterized by 10-12% needle and thread and 25-35% short grasses. Compared to the HCPC, water flow patterns are more numerous than expected, there is slight to moderate active pedestalling, there is more bare ground than expected, there is moderate movement of smaller size litter deposits into depressions or up against obstructions, infiltration is slightly to moderately affected by the shift toward more short grasses in the plant community. The reproductive capabilities of bluebunch wheatgrass and western wheatgrass are somewhat limited relative to recent climatic conditions (USDI and USDA 2000). Except for in the western portions of the Glaciated Plains where it often remains as the dominant species, bluebunch wheatgrass composition significantly declines in the central glaciated plains. Community A is less resilient and much less resistant than the HCPC. Although it can improve to the HCPC through successional processes, further disturbance will result in regression to a lower state. Once Community A regresses to a lower state, normal successional processes are often restricted.

Pathway 1.1A
Community 1.1 to 1.2

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

Pathway 1.2A
Community 1.2 to 1.1

Fire, prescribed grazing Favorable growing conditions, the implementation of prescribed grazing, or periodic fire will move Plant Community A to the HCPC. This succession is possible within a couple of years.

State 2
Degraded State

Community 2.1
Plant Community B Short and medium-height cool and warm-season perennial grasses, increase of lower-successional forbs and half-shrubs, increase of pricklypear cactus and annual grasses

Short and medium-height cool and warm-season perennial grasses, increase of lower-successional forbs and half-shrubs, increase of pricklypear cactus and annual grasses This Community is dominated by a mix of short height, cool and warm season grasses. Western wheatgrass and bluebunch wheatgrass represent less than 10% of total annual production. Blue grama, threadleaf sedge, sandberg bluegrass and other low successional grasses expanded their influence in the community. Needleandthread represents about 30% of total annual production. Hoods phlox, wild onion, western yarrow, green sagewort, scarlet globemallow and clubmoss increased and now contribute 15-20% of the total annual production. Clubmoss cover is often positively related to the presence of an argillic horizon in the soil. The density of fringed sagewort and broom snakeweed (warm season half-shrubs) increased relative to their presence in the higher successional communities. Pricklypear and brittle cactus are usually present in this community. Japanese brome, cheatgrass, and other annual plants are present in most disturbed areas. Total annual production varies from 200-400 lbs/ac. In comparison to the HCPC, litter varies from 20-30%. Bare ground increases to 30-40%.

Community 2.2
Plant Community C Half-shrubs, short cool- and warm-season perennial grasses, clubmoss, lower-successional forbs, pricklypear cactus, and annual grasses

Half-shrubs, short cool- and warm-season perennial grasses, clubmoss, lower-successional forbs, pricklypear cactus, and annual grasses This community is dominated by fringed sagewort and broom snakeweed. Silver sagebrush and pricklypear cactus are usually present. Short grasses (blue grama, prairie junegrass, sandberg blue grass, etc.) contribute from 50-60% of the total annual production. The short grasses, along with clubmoss often form a dense sod. Needleandthread contributes another 30% of the total annual production. High-successional perennial grasses contribute less than 5% of total annual production. Japanese brome and cheatgrass occur in disturbed areas, and as scattered plants dispersed throughout the shortgrass sod. Total annual production varies from 200-350 lbs/ac. Litter averages 15%. Bare ground usually varies from 20-35%.

Pathway 2.1A
Community 2.1 to 2.2

No fire, non-prescribed grazing, drought (3 to 5 years) Communities B and C are resistant to disturbances. However, they do not have a precise assemblage of species for which the proportions are the same from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. Environmental factors such as rainfall, grazing pressure, and fire will cause species composition shifts within these communities. Community B usually shifts toward C with adverse conditions.

Pathway 2.2A
Community 2.2 to 2.1

Fire, prescribed grazing Communities B and C are resistant to disturbances. However, they do not have a precise assemblage of species for which the proportions are the same from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. Environmental factors such as rainfall, grazing pressure, and fire will cause species composition shifts within these communities. Community C tends to shift to B with favorable conditions.

Transition T1A
State 1 to 2

Extended drought (greater than 7 years), non-prescribed grazing, no fire Community A will regress to Communities B or C in State 2 under non-prescribed grazing, prolonged drought, or an extended period lacking a natural fire regime. The rate of regression varies with the intensity of the disturbances. Severe drought may cause retrogression within a couple of years.

Restoration pathway R2A
State 2 to 1

Favorable precipitation for extended period, prescribed grazing, fire Communities B and C are resistant to change and do not readily shift to another State. Prescribed grazing reduces the probability of further regression in this State, but it does not ensure significant succession to State 1. In some places the soil and hydrology of the site has been altered by the shift from tall and mid grasses in the HCPC to the short grasses and half shrubs in these communities. Therefore, these communities represent a steady state, and they often remain there. Steady-state plant communities change only as a result of natural events that are beyond the normal range of events or as a result of human actions. An extended period of favorable precipitation combined with prescribed grazing and the re-introduction of fire into the system may induce significant succession (Branson and Miller 1981). This potential is depicted by the dashed line in the state and transition diagram. Mechanical treatments and range seeding are not normally recommended on this site.