Ecological dynamics
The Calcareous Rim Prairie ecological site is characterized by three states: the Reference State, the Tillage State, and the Woodland State. The Reference State includes two communities. The High Diversity Prairie, is characterized by a fire return interval of 3 years or less and the Old Growth Prairie is characterized by a fire return interval of up to 5 years. Grazing can also be a trigger for change on this ecological site. The Tillage State includes the Row Crop Community and the Seeded Grassland Community. State 3 in this model describes a woodland on untilled soils dominated by boxelder, green ash, willow, and cottonwood.
Previously tilled sites may revert to a woodland through abandonment; however, this is a very small percentage of acreage in MRLA 103 and not currently a community within this state and transition model (STM).
State 1
Reference State
This site is characterized as a wet prairie, which include a diversity of grasses, sedges, and forbs tolerant of poorly drained soils and calcareous conditions. Important species on this site include prairie cordgrass (Spartina pectinata Bosc ex Link), big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans (L.) Nash). Sedges are an important component. Several species are possible including Bicknell’s sedge (Carex bicknellii Britton), woolly sedge (Carex pellita Muhl. ex Willd.), and Buxbaum’s sedge (Carex buxbaumii Whalen.). Tussock-forming species like Hayden’s sedge (Carex haydenii Dewey) and upright sedge (Carex stricta Lam.) are also common.
Orchids like the white lady’s slipper (Cypripedium candidum Muhl. ex Willd.) is an important species that can reflect the high calcium carbonate content. Common forbs include prairie blazing star (Liatris pycnostachya Michx.), compassplant (Silphium laciniatum L.), fourflower yellow loosestrife (Lysimachia quadriflora Sims), and swamp milkweed (Asclepias incarnata L.). Shrubs, such as willows (Salix L.) and dogwoods (Cornus L.), increase with the absence of frequent fire.
Today, high-quality, unplowed areas are extremely uncommon. Most remaining areas managed for tallgrass prairie were once tilled and utilized for agricultural production. It is therefore likely that hydrology has been altered and many of the historic native prairie species are extirpated even from these sites.
Resilience management. Prescribed fire and managed grazing are key resilience management practices. Prescribed fire is the controlled application of fire to modify vegetation structure and influence ecological processes. Prescribed grazing incorporates periods of grazing rest during the growing season which benefits tallgrass maintenance. Excessive grazing can quickly impact the vegetative composition and negatively impact soil stability.
Community 1.1
High Diversity Prairie
This plant community consists of native grasses and forbs that are tolerant of poorly drained soils and soils with a high calcium carbonate content. The vegetative composition of the reference state can be influenced by grazing or fire. Fire is an important trigger in maintaining a native grassland community. The communities described within this state and transition model are influenced primarily by a fire return intervals of less than 3 years. Fire reduces the extent of woody species and maintains the natural dominance and diversity of native grasses and forbs. Fire stimulates seed regeneration and reduces the amount of thatch.
Common grasses include prairie cordgrass, big bluestem, and multiple species of sedges. Other wet-tolerant grass and herbaceous species will be present. The composition of forbs is often highly diverse. An orchid, the white lady's slipper (Cypripedium candidum Muhl. ex Willd.), is a species that reflects the high calcium carbonate content of this site. Wet prairie forbs are characteristic.
Resilience management. Prescribed fire and managed grazing are key resilience management practices. Prescribed fire is the controlled application of fire to modify vegetation structure and influence ecological processes. Prescribed grazing incorporates periods of grazing rest during the growing season which benefits tallgrass maintenance. Excessive grazing can quickly impact the vegetative composition and negatively impact soil stability.
Community 1.2
Old Growth Prairie
This plant community is characterized by a fire return interval of 3 to 5 years. Grass species are still dominant, but woody species have increased. Thatch is denser which can reduce seedling regeneration by shading and obstruction.
Resilience management. Prescribed fire and grazing are resilience management practices. Although this community has a longer fire return interval than Community 1.1, it also relies on fire and grazing to maintain vegetation community structure.
Pathway 1.1A
Community 1.1 to 1.2
The frequency of fire is the primary factor affecting the transition from Community 1.1 and Community 1.2. Pathway 1.1A consists of a fire free period of 3 to 5 years. It allows for changes such as an increase in number of shrub species, an increase in abundance of dead plant material, and a reduced rate of regeneration. Secondary triggers, such as grazing and drought, also influence overall community composition.
Pathway 1.2A
Community 1.2 to 1.1
This pathway consists of a fire return interval of less than 3 years. Fire intolerant woody species are set back, and the amount of dead plant material that can slow new growth is reduced.
State 2
Tillage State
Tillage is the primary mechanism affecting the transition to this state. In this state, dynamic soil properties such as bulk density, structure, organic carbon content, and saturated hydraulic conductivity are altered by agricultural practices. Hydrological modifications (tiling and ditching) are commonly installed to improve drainage, so natural hydrology is altered. Most areas in this state will remain in use for crop production in the foreseeable future – primarily in an intensive corn and soybean rotation.
Certain practices can mitigate the impacts of traditional agricultural practices on soil health. Conservation tillage minimizes soil disturbance and can improve soil structure and overall soil health. Corn or soybean plantings and a cover crop rotation can build soil structure, improve infiltration rates, reduce runoff and erosion, and protect water quality.
A small percentage of this ecological sites have been seeded back to grass. Some previously tilled areas have been converted to warm-season grasslands as part of the NRCS Conservation Reserve Program (CRP). Species seeded will depend upon the hydrology of the site and landowners objectives. Native forbs are commonly included in seed mixes to benefit wildlife and pollinators. Although highly beneficial to wildlife, these sites generally lack the diversity of State 1.
Cool-season grasses are also feasible. The most common cool-season grasses are non-native species, such as reed canarygrass and Kentucky bluegrass. Although cool-season grasslands are not as species rich or biologically diverse as warm-season grasslands, they still offer soil health benefits and benefits for grassland birds.
Some tilled sites may revert to a woodland through abandonment; however, this is a small percentage of acres within MLRA 103 so is not currently given a community in this model.
Resilience management. Disturbance management and harvest management are resilience management practices. The maintenance of this state requires that the intensity, frequency, duration, and timing of agricultural practices (disturbances) be managed to control or modify vegetation structure.
Community 2.1
Row Crop Community
This plant community typically consists of intensively produced, traditional row crops. Tillage and intentional plant establishment (crop seeding) are the primary triggers for this community. A secondary trigger is substantial hydrological modifications (ditching and tiling), which are commonly installed to improve soil drainage. The most common crops are corn and soybeans on an annual rotation. Many crops, however, are feasible for these areas.
Conservation tillage practices may be implemented to reduce the hazard of erosion while still maintaining a corn and soybean rotation. These practices can help protect the soil surface from erosion and allow water to infiltrate instead of running off. Examples include no-till or ridge-till, which leave residue on the surface of the field. Additional soil health benefits can be gained by adding alternative crops to fields that are already in conservation tillage. By diversifying the crop rotation, landowners take additional management steps to improve soil health and protect water quality.
Resilience management. Disturbance management and harvest management are resilience management practices. The maintenance of the desired vegetation community requires management of the intensity, frequency, duration, and timing of disturbances caused by agricultural practices.
Community 2.2
Seeded Grassland Community
This community is in areas that were previously tilled and used for agricultural production but have been transitioned to either warm-season or cool-season grasses. The primary trigger is the intentional establishment of a grassland community. Warm-season grasses are commonly planted through conservation programs, such as the NRCS Conservation Reserve Program (CRP). Species planted will depend upon the hydrology and landowner objectives. Commonly included are a mix of native forbs that benefit wildlife and pollinators. Numerous native grasses and forbs are suitable for this site. Seed mix selection depends on landowner objectives and site-specific characteristics.
Grazing management may also be a trigger. Poor grazing management practices on can lead to soil erosion and invasion by cool-season grasses such as smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis). Resilience management practices include prescribed fire, invasive plant management, and a program of planned grazing that manages the intensity, frequency, and duration of grazing.
Less common than warm-season species, but still feasible, are cool-season grass species such as reed canarygrass and Kentucky bluegrass. Many cool-season grasses can be planted, depending on the hydrology and landowner goals. Many of these areas are eventually transitioned to annual crop production.
Resilience management. Disturbance management and harvest management are resilience management practices. The maintenance of the desired vegetation structure requires management of the intensity, frequency, duration, and timing of disturbances caused by agricultural practices. Practices include seeding, controlling weeds and brush, and applying fertilizer.
Prescribed fire is a resilience management practice on warm-season grasslands. The controlled application of fire modifies vegetation structure and influence ecological processes.
Pathway 2.1.A
Community 2.1 to 2.2
This pathway converts Community 2.1 (row crops) to Community 2.2 (seeded grassland). The primary mechanism of change is the seeding of desired grass species.
Forage and Biomass Planting |
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Pathway 2.2.A
Community 2.2 to 2.1
This pathway converts seeded grassland to cropland. This is a common pathway throughout MLRA 103 as areas are placed in crop production. The mechanisms of change are tillage and intentional plant establishment (crop seeding). Resilience management practices include weed control (herbicide application), field cultivation, fertilizer application, and harvest management.
State 3
Woodland State
In the absence of a natural fire regime or grassland management, this site will transition to a Wooded State. Unmanaged grazing, altered hydrology, and invasive species may impact the site. Community composition will vary depending on the type and severity of disturbances. Dominant tree species often include eastern cottonwood, black willow, green ash, and boxelder. Reed canarygrass, Kentucky bluegrass, and smooth brome are often present.
Few acres within MLRA 103 are in this State. Some remaining areas are conservation easements. Areas not in a conservation programs are likely to be jurisdictional wetlands, making it very unlikely they will be transitioned to the State 2 due to various wetland programs and laws, including the Swampbuster provision of the Food Security Act of 1985 (P.L. 99-198, as amended by P.L. 115-25) and the Minnesota Wetland Conservation Act (WCA) of 1991 (M.R. 8420.0100, as amended in 2009).
Community 3.1
Woodland Community
This site is a woodland plant community usually consisting of various species of trees, shrubs, and often, non-native species. The composition and structure of this community will depend on the hydrology (natural or altered), previous and ongoing disturbances (tree removal, grazing), and available seed sources. Non-native shrub and herbaceous species are often present.
Transition T1A
State 1 to 2
Transition T1A is the conversion of the reference state to agriculture. The triggers are tillage and intentional plant establishment (crop seeding). Hydrological modifications, such as ditching and tiling, are often also installed.
Constraints to recovery. Tillage and long-term intensive agricultural production generally preclude a return to State 1. Areas in row crop production may be placed in conservation programs and seeded with warm-season grasses, but will not exhibit the natural species diversity or ecological resilience of State 1. Most acres converted to agriculture will stay as such for the foreseeable future.
Transition T1B
State 1 to 3
Plant community succession due to lack of natural fire and/or grazing. Brush and trees will increase and community structure will transition from a prairie to a woodland. Disturbances such as overgrazing and non-native vegetation may influence the plant community composition and structure.
Restoration pathway R3A
State 3 to 1
Sites that have not been tilled and still have natural hydrology may be feasible for restoration. Restoration activities will include woody species removal, weed/brush control, establishment of a native grassland community.