Ecological dynamics
The site developed under Northern Great Plains climatic conditions, and included natural influence of large herbivores and occasional fire. Changes will occur in the plant communities due to climatic conditions and/or management actions. Due to the nature of the soils, the site is considered quite stable. Under continued adverse impacts, a slow decline in vegetative vigor and composition will occur. Under favorable vegetative management treatments the site can quickly return to the Reference Plant Community.
The plant community upon which interpretations are primarily based is the Reference Plant Community. The Reference Plant Community has been determined by study of rangeland relic areas, areas protected from excessive disturbance, and areas under long-term rotational grazing regimes. Trends in plant community dynamics ranging from heavily grazed to lightly grazed areas, seasonal use pastures, and historical accounts also have been used. Subclimax plant communities, states, transitional pathways, and thresholds have been determined through similar studies and experience.
Continuous grazing without adequate recovery periods following each grazing occurrence over several years causes this site to depart from the Reference Plant Community. Species such as western wheatgrass, blue grama, sedges, cudweed sagewort, hairy golden aster, prairie coneflower, scurfpea and fringed sagewort will initially increase. Prairie sandreed, sand bluestem green needlegrass, false gromwell, vetch, penstemon and leadplant will decrease in frequency and production. In time, heavy continuous grazing will likely cause upland sedges and blue grama to dominate and pioneer perennials, annuals, and club moss (in its range) to increase. This plant community is relatively stable and the competitive advantage prevents other species from establishing. This plant community is less productive than the Reference Plant Community. Runoff increases and infiltration will decrease. Soil erosion will be minimal.
Extended periods of non-use and/or lack of fire will result in a plant community having high litter levels, which favors an increase in Kentucky bluegrass and/or smooth bromegrass, and in time, shrubs such as western snowberry and silver sagebrush will increase.
Due to a general invasion of exotic species (such as Kentucky bluegrass and smooth bromegrass) across the MLRA within this site, returning to the 1.1 Western Wheatgrass/Tall Warm-Season Plant Community Phase may not be possible. Today, the 2.1 Blue Grama/Sedge/Western Wheatgrass Plant Community Phase most resembles the 1.1 Reference Plant Community Phase in appearance and function.
Following the state and transition diagram are narratives for each of the described states and community phases. These may not represent every possibility, but they are the most prevalent and repeatable states/community phases. The plant composition tables shown below have been developed from the best available knowledge at the time of this revision. As more data are collected, some of these community phases and/or states may be revised or removed, and new ones may be added. The main purpose for including the descriptions here is to capture the current knowledge and experience at the time of this revision.
State 1
Grassland State
The Grassland State is supported by empirical data, historical data, local expertise, and photographs. This state is defined by two native plant communities that are a result of periodic fire, drought, and grazing. These events are part of the natural disturbance regime and climatic process. The Reference Plant Community consists of both warm- and cool-season, tall- and midgrasses, forbs, shrubs. Plant Community 2 consists of decadent plants or excessive litter, and few remnant native grasses and forbs.
Community 1.1
Reference Plant Community
This is the interpretive plant community and is considered to be the Reference Plant Community. This community evolved with grazing by large herbivores and occasional prairie fire. It is well suited for grazing by domestic livestock and can be found on areas that are properly managed with prescribed grazing that allows for proper utilization, changes in season of use and adequate recovery periods following each grazing event.
The potential vegetation is about 82% grasses or grass-like plants, 10% forbs, and 8% shrubs. Cool-season and tall warm-season grasses dominate the plant community. The co-dominant grasses include western wheatgrass and prairie sandreed. Other grasses and grass-like plants occurring on the site include needleandthread, green needlegrass, blue grama, prairie junegrass and sedges. Significant forbs include stiff sunflower, false gromwell, silverleaf scurfpea, western yarrow and goldenrod. In many areas western snowberry is the principle shrub and occurs in patchy mosaic. In other areas, silver sagebrush is the dominant shrub and occurs more evenly dispersed across the site. Other shrubs include prairie rose, leadplant and fringed sagewort.
This plant community is well adapted to the Northern Great Plains climatic conditions. Individual species can vary greatly in production depending on growing conditions (timing and amount of precipitation and temperature). Community dynamics, nutrient cycle, water cycle and energy flow are functioning properly. Plant litter is properly distributed with very little movement off-site and natural plant mortality is very low. The diversity in plant species allows for high drought tolerance. Low available water capacity coupled with high accumulations of sodium and slow permeability strongly influences the soil-water-plant relationship.
Table 5. Annual production by plant type
| Plant type |
Low
(kg/hectare) |
Representative value
(kg/hectare) |
High
(kg/hectare) |
| Grass/Grasslike |
1154 |
1597 |
1939 |
| Forb |
84 |
135 |
179 |
| Shrub/Vine |
11 |
56 |
90 |
| Moss |
– |
6 |
22 |
| Total |
1249 |
1794 |
2230 |
Community 1.2
Non-Use Community
This plant community develops after an extended period of 15 or more years of non-use by herbivores and exclusion of fire. This plant community is dispersed throughout the pasture, encircling spot grazed areas, and areas distant from water sources. This is a typical pattern found in properly stocked pastures grazed season-long. Plant litter accumulates in large amounts as this community develops. Litter buildup reduces plant vigor and density, and seedling recruitment declines. Eventually litter levels become abundant enough to crowd out living plants and reduce plant density. Annual and/or biennial forbs, annual grasses, and cryptogams commonly fill these interspaces.
Due to a lack of tiller stimulation and sunlight, native bunchgrasses typically develop dead centers and native rhizomatous grasses are limited to small colonies. Heavy litter covers shorter understory species (i.e. short grasses and sedges) restricting their ability to capture adequate sunlight for photosynthesis. Vigor and diversity of native plants are reduced.
Non-native grasses, such as Kentucky bluegrass, crested wheatgrass, smooth bromegrass and cheatgrass tend to dominant this plant community. Other grasses that may be present include western wheatgrass, needleandthread, green needlegrass and Sandberg bluegrass. The common forbs include sweetclover, green sagewort, cudweed sagewort and heath aster. Fringed sagewort, snowberry and/or silver sagebrush are the principal shrubs and tend to increase in density and cover.
This plant community is resistant to change without prescribed grazing or fire. The combination of both grazing and fire is most effective in moving this plant community towards the Reference Plant Community. Soil erosion is low. Compared to the Reference Plant Community, infiltration is reduced to the lower root zone. Runoff is similar to the Reference Plant Community. This plant community tends to be moisture loving and usually tends to utilize the spring moisture quickly causing forage base to become dry and not very palatable early in the summer. Once this plant community is reached, time and external resources will be needed to see any immediate recovery in the diversity of the site.
Pathway 1.1 to 1.2
Community 1.1 to 1.2
Non-use and no fire for extended periods of time will convert this plant community to the Excessive Litter Plant Community.
Pathway 1.2 to 1.1
Community 1.2 to 1.1
With prescribed grazing and/or prescribed burning, this plant community will move toward the Western Wheatgrass/Tall Warm-Season Plant Community. This would require long-term management with prescribed grazing and/or prescribed burning under controlled conditions.
| Prescribed Burning |
|
| Prescribed Grazing |
|
State 2
Shortgrass State
With heavy, continuous grazing blue grama will become the dominant species and have a sod bound appearance. Unable to withstand the grazing pressure, only a remnant population of western wheatgrass remains.
Species diversity has been reduced further. Water infiltration is reduced due to the sod nature of the buffalograss and blue grama. Runoff is increased.
Community 2.1
Shortgrass Community
This plant community can quickly develop from the adverse effects of heavy, continuous grazing and/or annual, early spring seasonal grazing. Annual grazing too early in the spring depletes stored carbohydrates, resulting in weakening and eventual death of the cool season mid-grasses. Short grasses and grass-likes and forbs increase to dominate the site and annual production decreases dramatically. Lack of litter and reduced plant vigor result in higher soil temperatures, poor water infiltration rates, and high evapotranspiration, which gives blue grama and sedges a competitive advantage over cool season mid-grasses. This plant community can occur throughout the pasture, on spot grazed areas, and around water sources where season-long grazing patterns occur.
Blue grama, sedges and western wheatgrass are the dominant species. Other grasses that may be present include Sandberg bluegrass, red threeawn, needleandthread, prairie junegrass and annual grasses. Forbs such as hairy goldaster, cudweed sagewort, heath aster, Lambert crazyweed, prairie coneflower, scurfpea and western yarrow may also be present. There is usually less than 10% bare ground.
This plant community is relatively stable. The thick sod and competitive advantage prevents other species from establishing. This plant community is less productive than the Reference Plant Community. Runoff increases and infiltration will decrease. Soil erosion will be minimal due to the sod forming habit of blue grama.
State 3
Club Moss State
The Club Moss State is supported by empirical data, historical data, local expertise, and photographs. This state represents a plant community change as well as changes to the energy flow and nutrient cycling processes. This state is defined by one plant community.
Community 3.1
Club Moss Community
A dense sod of club moss dominates this plant community. Club moss occupies bare soil areas within deteriorated or disturbed higher successional plant communities due to long-term repeated disturbances. Club moss cover is often 25% or greater. Club moss creates a more arid microclimate, resulting in extreme competition for available moisture. Initial runoff rates are low but then increase as clubmoss becomes saturated. Once clubmoss has been saturated then runoff increases and infiltration decreases as compared Reference Plant Community. Vigor and production of other species are reduced dramatically.
Grasses and grass-like plants include western wheatgrass, blue grama, Sandberg bluegrass and upland sedges. Forbs commonly found in this plant community include cudweed sagewort, hairy goldenaster, heath aster, prairie coneflower, scurfpea, annual deervetch and western yarrow. When compared to the Western Wheatgrass/Tall Warm-Season Plant Community, blue grama and club moss have increased, while western wheatgrass has decreased and the tall warm-season grasses have disappeared.
State 4
Annual/Pioneer State
The Annual/Pioneer State is supported by empirical data, historical data, local expertise, and photographs. This state represents a plant community change as well as changes to the energy flow and nutrient cycling processes. This state is defined by one plant community.
Community 4.1
Pioneer Community
This plant community develops under severe disturbance and/or excessive defoliation. This can result from heavy livestock or wildlife concentration, and cropping abandonment (go-back land). The dominant vegetation includes pioneer annual grasses, forbs, invaders, and early successional biennial and perennial species. Grasses may include red threeawn, smooth bromegrass, crested wheatgrass, annual brome, needleandthread, prairie junegrass and western wheatgrass. The dominant forbs include curlycup gumweed, marestail, salsify, kochia, field bindweed, thistles, western ragweed, pussytoes, prostrate verbena and other early successional species. Shrubs that may be present include prairie rose, fringed sagewort and broom snakeweed. Plant species from adjacent ecological sites may become minor components of this plant community. The community also is susceptible to invasion of non-native species due to severe soil disturbances and relatively high percent of bare ground. Many annual and perennial forbs, including non-native species, have invaded the site.
This plant community is resistant to change, as long as soil disturbance or severe vegetation defoliation persist, thus holding back secondary plant succession. Soil erosion is potentially high in this vegetation state. Reduced surface cover, low plant density, low plant vigor, loss of root biomass, and soil compaction, all contribute to decreased water infiltration, increased runoff, and accelerated erosion rates.
Significant economic inputs, management and time would be required to move this plant community toward a higher successional stage and a more productive plant community. Secondary succession is highly variable, depending upon availability and diversity of a viable seed bank of higher successional species within the existing plant community and neighboring plant communities. This plant community can be renovated to improve the production capability, but management changes would be needed to maintain the new plant community.
Transition T 1 to 2
State 1 to 2
Heavy, continuous grazing or continuous seasonal grazing will convert the plant community to the Blue Grama/Sedge/Western Wheatgrass Plant Community.
Transition T 1 to 4
State 1 to 4
Excessive defoliation (i.e., areas of heavy animal concentration) or cropped go-back land with continuous grazing will convert the plant community to the Annual/Pioneer Perennial Plant Community.
Restoration pathway R 2 to 1
State 2 to 1
Long-term prescribed grazing that includes changing season of use and allowing adequate recovery periods to enhance cool season grasses will lead this plant community back to the Western Wheatgrass/Tall Warm-Season Plant Community.
Transition T 2 to 3
State 2 to 3
Heavy, continuous grazing may cause further deterioration resulting in a shift to the Club Moss Plant Community.
Restoration pathway R 3 to 1
State 3 to 1
Fertilization combined with prescribed grazing will move this plant community subsequently through the successional stages leading toward the Western Wheatgrass/Tall Warm-Season Plant Community.
Mechanical renovation followed by prescribed grazing will reduce club moss, increase western wheatgrass, and eventually shift this plant community back toward the Western Wheatgrass/Tall Warm-Season Plant Community.
Prescribed burning followed by prescribed grazing may eventually convert this plant community back to the Western Wheatgrass/Tall Warm-Season Plant Community.
Long-term prescribed grazing may eventually moves this plant community through the successional stages leading toward the Western Wheatgrass/Tall Warm-Season Plant Community.
Restoration pathway R 4 to 1
State 4 to 1
Under long-term prescribed grazing and/or removal of disturbance, including adequate rest periods, this plant community will move through the successional stages, and may eventually lead to the Western Wheatgrass/Tall Warm-Season Plant Community. Depending on the slope, aspect, and size, and if adequate perennial plants exist, this change can occur more rapidly. This process will likely take a long period of time (50+ years).
Range seeding with deferment and long term prescribed grazing can convert this to a plant community resembling the Western Wheatgrass/Tall Warm-Season Plant Community.
