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 Common Rivergrass/Slough Sedge 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, community pathways, states, transitions, thresholds and restoration pathways have been determined through similar studies and experience.
This ecological site (ES) 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 changed the disturbance regime of this site. Heavy continuous grazing without adequate recovery periods following each grazing occurrence causes this site to depart from the Reference State. Species such as fowl bluegrass, spikerush, and Baltic rush will initially increase. Common Rivergrass and slough sedge will decrease in frequency and production. Continued heavy grazing eventually causes a dominance by spikerush, rushes, and unpalatable forbs such as curly dock.
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.
The following is a diagram that illustrates the common plant community phases that can occur on the site and the transition and community pathways between them. The ecological processes will be discussed in more detail in the plant community descriptions following the diagram.
State 1
Reference State
The Reference State represents the natural range of variability that dominates the dynamics of this ES. This state is typically dominated by cool-season grass and grass-like species. Before European settlement, the primary disturbance mechanisms for this site in the reference condition included periodic fire, grazing by large herding ungulates, and fluctuations in the water table and ponding frequency and duration. Frequent surface fires (3 to 5 years) 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, concentrated livestock grazing, and weather fluctuations. Species that are desirable for livestock and wildlife can decline and a corresponding increase in less desirable species will occur.
Community 1.1
Common rivergrass-Slough Sedge
Interpretations are based primarily on the 1.1 Common Rivergrass-Slough Sedge Plant Community Phase (this is also considered to be climax). This plant community evolved with grazing by large herbivores, frequent surface fires, and periodic flooding events and is suited for grazing by domestic livestock. This plant community can be found on areas that are grazed and where the grazed plants receive adequate periods of rest during the growing season in order to recover. The potential vegetation is about 45 percent grasses, 40 percent grass-likes, and 15 percent forbs. The major grasses and grass-likes include Common rivergrass, slough sedge (also called wheat sedge), woolly sedge (Carex pellita), American mannagrass (Glyceria grandis), prairie cordgrass, and spikerush. Key forbs include smartweeds (Polygonum), western dock (Rumex aquaticus), and white panicle aster (Symphyotrichum lanceolatum).
This plant community phase is diverse, stable, and productive, and is well adapted to the Northern Great Plains. The high water table supplies much of the moisture for plant growth. 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 variability of both the fluctuations of water table and reoccurring ponding allows for the diversity in plant species. This is a sustainable plant community in terms of soil stability, watershed function, and biologic integrity.
Community 1.2
Slough Sedge-Spikerush
This plant community will slowly develop from the adverse effects of continuous grazing, without adequate recovery periods between each grazing event during the growing season. When compared to the 1.1 Common rivergrass-Slough Sedge Plant Community Phase, Common rivergrass, Prairie cordgrass, and American mannagrass have decreased. The grass-like species, such as slough sedge, spikerush, woolly sedge, and rushes, have increased and tend to dominate this plant community.
Pathway 1.1
Community 1.1 to 1.2
Heavy continuous grazing which includes herbivory at moderate to heavy levels at the same time of year each year without adequate recovery periods, or during periods of below normal precipitation when grazing frequency and intensity increases on these sites due to limited forage availability on adjacent upland sites will shift this community to the 1.2 Slough Sedge-Spikerush Plant Community Phase.
Pathway 1.2
Community 1.2 to 1.1
Prescribed grazing (alternating season of use and providing adequate recovery periods) or periodic light to moderate grazing possibly including periodic rest will convert this plant community to the 1.1 Common rivergrass-Slough Sedge Plant Community Phase. This pathway could also occur with a return to more normal precipitation levels and frequencies.
State 2
Invaded State
This state is characterized by the increase in bare ground due to trampling caused by excessive use and/or by inundation for extended periods which causes a temporary shift in the plant composition and cover. This allows for the invasion of nonnative species, which, with continued heavy grazing, can increase to eventual dominance. Loss or reduction of native cool- and warm-season species can negatively impacted energy flow and nutrient cycling. Infiltration will be reduced and native plant mortality will increase. As the disturbance level increases, native 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
Annual Pioneer-Perennial Pioneer
This plant community developed with heavy continuous grazing without adequate recovery periods between grazing events and no surface fire or abandonment after cropping. The dominant vegetation includes pioneer annual and/or perennial native and non-native grasses, grass-likes, forbs, and shrubs. Grasses may include foxtail barley (Hordeum jubatum), rough barnyard grass (Echinochloa muricata), quackgrass, fowl bluegrass, Kentucky bluegrass, Baltic rush (also known as mountain rush), and sedges. The dominant forbs include knotweed (Polygonum), Canada thistle (Cirsium arvense), and other early successional species. This is due to the loss of diversity (including the loss of the seed bank), within the existing plant community, and the plant communities on adjacent sites.
Significant economic inputs, management, and time would be required to move this plant community toward a higher successional stage. Secondary succession is highly variable, depending upon availability and diversity of a viable reproductive source of higher successional species.
Community 2.2
Spikerush-Baltic Rush-Fowl Bluegrass-Forbs
This plant community developed with heavy continuous grazing without adequate recovery periods between grazing events and/or inundation during periods of extended above-average precipitation. Spikerush, Baltic rush, bulrush (Schoenoplectus), and other less desirable grass-likes, along with grasses such as fowl bluegrass, and American sloughgrass (Beckmannia syzigachne), dominate the community. Quackgrass (Elymus repens), creeping meadow foxtail (Alopecurus arundinaceus), Kentucky bluegrass (Poa pratensis), and other nonnative species can invade on drier portions of the community. Common rivergrass, slough sedge, other sedges, prairie cordgrass, and reedgrass (Calamagrostis) will be virually eliminated from the plant community. Smartweed (Polygonum), dock (Rumex), and cinquefoil (Potentilla) have increased. Areas of bare ground can be present throughout the site.
A significant amount of production and diversity has been lost when compared to the 1.1 Common rivergrass-Slough Sedge Plant Community Phase. Loss or reduction of native grasses, grass-likes, and forbs has negatively impacted energy flow and nutrient cycling. It will take a long time to restore this plant community with improved management or return of more normal precipitation patterns.
Dominant plant species
-
spikerush (Eleocharis), grass
-
mountain rush (Juncus arcticus ssp. littoralis), grass
-
bulrush (Schoenoplectus), grass
-
fowl bluegrass (Poa palustris), grass
-
American sloughgrass (Beckmannia syzigachne), grass
-
quackgrass (Elymus repens), grass
-
creeping meadow foxtail (Alopecurus arundinaceus), grass
-
Kentucky bluegrass (Poa pratensis), grass
-
knotweed (Polygonum), other herbaceous
-
dock (Rumex), other herbaceous
-
cinquefoil (Potentilla), other herbaceous
Pathway 2.1
Community 2.1 to 2.2
Heavy continuous grazing which includes herbivory at moderate to heavy levels at the same time of year each year without adequate recovery periods, or during periods of below normal precipitation when grazing frequency and intensity increases on these sites due to limited forage availability on adjacent upland sites and no surface fire for extended periods of time (typically for 10 years or more) causing litter levels to become high enough to reduce native grass vigor, diversity, and density will shift this community to the 2.2 Annual Pioneer-Perennial Pioneer Plant Community Phase.
Pathway 2.2
Community 2.2 to 2.1
Inundation for extended periods beyond normal ponding and drying patterns will convert this plant community to the 2.1 Spikerush-Baltic Rush-Fowl Bluegrass-Forbs Plant Community Phase within the Invaded State (State 2).
State 3
Crop Production State
This state is characterized by the production of annual crops using a variety of tillage and cropping systems along with management practices. Cropping on this site is enabled during years with drier than normal precipitation or with artificial drainage (surface or subsurface).
Dominant plant species
-
corn (Zea), grass
-
wheat (Triticum), grass
-
soybean (Glycine), other herbaceous
-
beet (Beta), other herbaceous
Community 3.1
Annual Crops
This plant community developed with the use of a variety of tillage systems and cropping systems for the production of annual crops including corn, soybeans, wheat, sugar beet and a variety of other crops.
Dominant plant species
-
corn (Zea), grass
-
wheat (Triticum), grass
-
beet (Beta), other herbaceous
-
soybean (Glycine), other herbaceous
Transition T1A
State 1 to 2
Heavy continuous grazing (stocking levels well above carrying capacity for extended portions of the growing season and often at the same time of year each year), no surface fire for extended periods of time (typically for 10 years or more) causing litter levels to become high enough to reduce native grass vigor, diversity, and density, and/or inundation for extended periods beyond normal ponding and drying patterns will eventually cause a shift over a threshold leading to the 2.1 Spikerush-Baltic Rush-Fowl Bluegrass-Forbs Plant Community Phase within the Invaded State (State 2). Grazing repeatedly in the early growing season can expedite this shift by causing mechanical disturbance due to trampling.
Transition T1B
State 1 to 3
Tillage, Artificial drainage (surface and subsurface) will cause a shift over a threshold leading to the 3.1 Annual Crops within the Crop Production State (State 3).
Restoration pathway R2
State 2 to 1
Long-term prescribed grazing (moderate stocking levels coupled with adequate recovery periods, or other grazing systems such as high-density, low-frequency intended to treat specific species dominance, or periodic light to moderate stocking levels possibly including periodic rest) may lead this plant community phase over a threshold to the Reference State (State 1). Wetland restoration techniques may be necessary to restore biotic integrity and plant diversity and productivity.
Transition T2
State 2 to 3
Tillage, Artificial drainage (surface and subsurface) will cause a shift over a threshold leading to the 3.1 Annual Crops within the Crop Production State (State 3).
Transition T3
State 3 to 2
Cropping followed by abandonment may lead this plant community phase over a threshold to the Invaded State (State 2) and more specifically to the 2.2 Annual-Pioneer-Perennial Pioneer Plant Community Phase.
