Ecological dynamics
The site developed under Northern Great Plains climatic conditions, and included natural influence of large herding herbivores and occasional fire. Changes will occur in the plant communities due to weather fluctuations and/or management actions. Under adverse impacts, a relatively rapid decline in vegetative vigor and composition can occur. Under favorable conditions the site has the potential to resemble the Reference State. Interpretations for this site are based primarily on the Wheatgrass/Cordgrass/Alkaligrass Plant Community Phase (1.1). This community phase and the Reference State 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 considered. Community phases and pathways, states, transitions, thresholds and restoration pathways have been determined through similar studies and experience.
The natural disturbance regime consisted of occasional fires caused both by natural and Native American ignition sources. Large ungulate grazing was heavy and occurred often, but usually for short durations. Grazing may have been severe when occurring after a fire event, or in areas near water sources. This ecological site has been grazed by domestic livestock since introduced into the area. The introduction of domestic livestock and the use of fencing and reliable water sources have radically changed the disturbance regime of this site. Heavy continuous grazing and/or continuous seasonal (spring) grazing, without adequate recovery periods following each grazing occurrence causes this site to depart from the Reference State. Species such as western wheatgrass and inland saltgrass will initially increase. Alkali cordgrass and Nuttall’s alkaligrass will decrease in frequency and production. Heavy continuous grazing causes foxtail barley, inland saltgrass, and unpalatable forbs such as silverweed cinquefoil and dock species to increase and western wheatgrass to decrease. Inland saltgrass can eventually form into a patchy sod and bare ground will typically increase around the sod patches. Increased surface salts are common due to loss of plant cover.
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
Reference
This state represents the natural range of variability that dominates the dynamics of this ecological site. This state is dominated by cool-season grasses, while warm-season grasses are subdominant. Pre-European settlement, the primary disturbance mechanisms for this site in the reference condition included occasional fire and grazing by large herding ungulates. Timing of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Today the primary disturbance is from a lack of fire and concentrated livestock grazing. Grasses that are desirable for livestock and wildlife can decline and a corresponding increase in less desirable grasses will occur.
Dominant plant species
-
western wheatgrass (Pascopyrum smithii), grass
-
Nuttall's alkaligrass (Puccinellia nuttalliana), grass
-
alkali cordgrass (Spartina gracilis), grass
-
prairie cordgrass (Spartina pectinata), grass
-
foxtail barley (Hordeum jubatum), grass
-
saltgrass (Distichlis spicata), grass
-
western dock (Rumex aquaticus), other herbaceous
-
silver cinquefoil (Potentilla argentea), other herbaceous
-
seepweed (Suaeda), other herbaceous
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redwool plantain (Plantago eriopoda), other herbaceous
Community 1.1
Wheatgrass/Cordgrass/Alkaligrass
This community evolved with grazing by large herbivores, occasional prairie fires, and periodic flooding events; it can be found on areas that are properly managed with grazing and/or prescribed burning and, sometimes, on areas receiving occasional short periods of rest. The potential vegetation is about 95 percent grasses and grass-like plants and 5 percent forbs. The major grasses include western wheatgrass, Nuttall’s alkaligrass, and alkali and prairie cordgrass. Other grasses present include slender wheatgrass, inland saltgrass, and foxtail barley. Salt tolerant forbs such as alkali plantain, western dock, and seepweed are common. Interpretations are based primarily on this plant community phase.
This community phase is diverse, stable, productive and well adapted to both saline soils and the Northern Great Plains climatic conditions. Community dynamics, nutrient cycle, water cycle, and energy flow are functioning properly. Litter is properly distributed with very little movement off-site and natural plant mortality is very low. This community is resistant to many disturbances except continuous grazing, tillage, and/or development into urban or other uses. The diversity in plant species allows for both the fluctuation of flooding as well as large seasonal variations.
Table 5. Annual production by plant type
| Plant type |
Low
(kg/hectare) |
Representative value
(kg/hectare) |
High
(kg/hectare) |
| Grass/Grasslike |
3099 |
4131 |
5139 |
| Forb |
39 |
128 |
241 |
| Total |
3138 |
4259 |
5380 |
| Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
| J |
F |
M |
A |
M |
J |
J |
A |
S |
O |
N |
D |
Community 1.2
Wheatgrass/Foxtail Barley/Inland Saltgrass
This community develops with heavy continuous grazing, with lack of adequate recovery periods during the growing season, and/or annual, early spring seasonal grazing. Lack of litter and reduced plant heights result in higher soil temperatures, poor water infiltration rates, high evapotranspiration, and upward percolation of the high water table; the impact is increased salt concentrations on the soil surface. This gives inland saltgrass and other salt tolerant species a competitive advantage over less tolerant species.
Nuttall’s alkaligrass, slender wheatgrass, prairie cordgrass, and alkali cordgrass have decreased while western wheatgrass and inland saltgrass will initially increase in composition. Mat muhly, foxtail barley, silverleaf cinquefoil, dock and plantain will also increase in composition. As long as the herbaceous component remains intact, the plant community tends to be resilient. However, species composition can be further altered through long-term, heavy continuous grazing. With loss of Nuttall alkaligrass, cordgrasses, slender wheatgrass, and much of the western wheatgrass, inland saltgrass will eventually become the dominant species.
This plant community is relatively stable and well adapted to increased salinity. Plant vigor, litter, plant density and production have decreased. The biological integrity and the water and nutrient cycles of this plant community are becoming impaired.
| Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
| J |
F |
M |
A |
M |
J |
J |
A |
S |
O |
N |
D |
Community 1.3
Wheatgrass/Alkaligrass
This plant community occurs when grazing is removed for long periods of time (rest) in the absence of fire. Plant composition is similar to community phase 1.1; however individual species production and frequency will be lower. Much of the nutrients are tied up in excessive litter. The nutrient cycle is slowed due to standing dead plant residues not in contact with a moist soil surface. Aboveground litter also limits sunlight from reaching plant crowns. Tall warm-season grasses (cordgrasses) die off or are reduced in density and vigor and typically develop into small but dense colonies. Thick litter and absence of grazing animals (animal impact) or fire reduces seed germination and establishment. This plant community develops after an extended period of 10 or more years of non-use by herbivores and exclusion of fire.
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 Wheatgrass/Cordgrass/Alkaligrass Plant Community Phase (1.1). Soil erosion is low and runoff is virtually unchanged.
| Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
| J |
F |
M |
A |
M |
J |
J |
A |
S |
O |
N |
D |
Pathway 1.1a
Community 1.1 to 1.2
Heavy continuous grazing (stocking rates well above capacity for extended portions of the growing season without adequate recovery) or heavy seasonal grazing (stocking rates well above capacity for a portion of the growing season, but at the same time of year every year and without adequate recovery) will shift the plant community phase to more grazing tolerant species. In pre-European times, this transition would have occurred following multiple disturbances such as extended periods of below average precipitation followed by heavy concentrations of large ungulate herbivory.
Pathway 1.1b
Community 1.1 to 1.3
Extended periods of non-use and no fire will tend to favor the cool-season grasses, and the warm-season grasses will decline.
Pathway 1.2a
Community 1.2 to 1.1
Prescribed grazing with adequate recovery between grazing events will allow the cordgrasses and Nuttall’s alkaligrass to increase in vigor and production. In pre-European times, this would have occurred where light to moderate disturbances from large ungulates occurred sporadically.
Pathway 1.3a
Community 1.3 to 1.1
Prescribed grazing (stocking levels which match the animals to the forage resource and allow adequate recovery periods between grazing events) coupled with prescribed burning (typically spring burning, but fall burning may also be effective) is the most effective method of effecting this shift.
State 2
Degraded
This State is characterized by the dominance of the shorter-statured, more saline tolerant species such as foxtail barley and inland saltgrass, the increase in bare ground, and the increased presence of salt accumulations on the soil surface. Infiltration is reduced, which allows the moisture and the salts carried by the moisture to be wicked up to the soil surface. The short-statured and shallow rooted species are more capable of withstanding the higher concentrations of salts in the soil surface. As the disturbance level increases, plant density decreases even more, giving way to annual species and invasive perennial species, as well as a further increase in bare ground.
Community 2.1
Foxtail Barley/Inland Saltgrass, Bare Ground
This plant community developed with heavy continuous season-long grazing where adequate recovery periods between grazing events were not allowed. Patches of inland saltgrass sod are typical and foxtail barley is well distributed throughout the community. Nuttall’s alkaligrass and western wheatgrass have been greatly reduced and may persist in remnant amounts, reduced in vigor. Bare ground may develop in micro lows where salt concentrations are highest. A white salt crust is common on the surface. Only a few very salt tolerant annuals, such as glasswort and seepweed, can survive.
This plant community is resistant to change due to the grazing tolerance of inland saltgrass and increased surface salts. A significant amount of production and diversity has been lost when compared to the Wheatgrass/Cordgrass/Alkaligrass Plant Community Phase (1.1). Loss of key cool-season grasses and increased bare ground has negatively impacted energy flow and nutrient cycling. Water infiltration is reduced significantly due to the shallow rooting depth of inland saltgrass, and increased bare ground.
Community 2.2
Annual/Pioneer, Non-Native Perennial, Bare Ground
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 foxtail barley, which will dominate along with fowl bluegrass, Nuttall’s alkaligrass, annual brome and western wheatgrass. The dominant forbs include curly dock, burningbush (kochia), and other early successional salt tolerant species. Plant species from adjacent ecological sites may become minor components of this plant community. The community is susceptible to invasion of non-native species due to severe soil disturbances and relatively high percent of bare ground.
This plant community is resistant to change, as long as soil disturbance or severe vegetation defoliation persists, thus holding back secondary plant succession. Soil erosion is potentially high in this plant community. 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. Due to the highly variable nature of the plant community that may exist, no growth curve has been assigned.
Pathway 2.2a
Community 2.2 to 2.1
This community pathway occurs with the passage of time as successional processes take place and native plant species gradually begin to establish on the site again.
State 3
Cropland
This state is the result of annual cropping
Transition T1a
State 1 to 2
This transition is a result of heavy, continuous season-long grazing (stocking levels well above recommended rates, for the entire growing season). Grazing pressure and physical impacts of livestock on the soil surface alter the plant community. The less grazing tolerant/more palatable plant species are reduced while the grazing tolerant species increase. Physical impacts result in increased bare ground which increases surface salinity and further enhances the salt tolerant species. The physical impacts (i.e., compaction) are greater when the soil surface is wet from short-term flooding or ponding events.
Transition T1b
State 1 to 3
This transition occurs with cessation of cropping practices being applied.
Transition T2a
State 2 to 3
This transition occurs with cessation of cropping practices being applied.
Transition T3a
State 3 to 2
Cropland abandonment. Attempts to crop these areas often fail, resulting in bare ground and weedy species such as kochia.
