Ecological dynamics
The Wet Footslope/Drainageway ecological site is characterized by three states: the Reference State (native prairie), the Tillage State, and the Woodland State.
In this model, two plant communities exist in the Reference State and are characterized by different fire return intervals. The first community is the High Diversity Prairie, which is characterized by a fire return interval of approximately 4 years or less. The second community is the Old Growth Prairie, which is characterized by a longer fire return interval. The Old Growth Prairie exhibits a continuing increase in woody vegetation. The mechanism of change between communities is fire frequency and the resulting effects fire has on the plant community. Grazing can also be a trigger for change on this ecological site.
The Tillage State describes sites that have been tilled and generally have modified hydrology (ditching, tiling). Two communities make up the Tillage State: the Row Crop Community and the Seeded Grassland Community. Transition mechanisms are traditional agriculture practices such as preparing the site, planting desired species, applying herbicide (weed control), applying fertilizer, and harvesting.
Some areas of this ecological site are in a Woodland State. Sites that lack a natural fire regime or managed grazing will eventually revert to a woodland. Sites may have other disturbances such as unmanaged grazing and non-native species. Dominant trees on these sites will vary depending on the hydrology, disturbances, and seed sources. State 3 in this model describes a woodland dominated by green ash, boxelder, cottonwood, and willow; however, community structure and composition will depending upon seed sources and the disturbance type and severity.
State 1
Reference State
The Wet Footslopes/Drainageway Prairies reference state is a native prairie that has a diversity of wet-tolerant grasses and forbs. Community phases within the Reference State are dependent upon the influences of the frequency of fire events. Fire is a natural trigger that promotes continued herbaceous vegetation dominance. Fire removes plant litter, helps cycle nutrients, and allows light to reach the seedbed. Frequent fire maintains the community in a grassland state, by keeping fire-sensitive woody species from proliferating.
A secondary trigger is grazing. Overgrazing will reduce the extent of highly palatable species thereby allowing the growth of less desirable plants to increase.
Reference plant communities are characterized as native tallgrass prairie, with a diversity of grasses, sedges, and forbs characteristic of poorly drained conditions. Variation in water table allows both wetland and non-wetland species to thrive. Prairie cordgrass (Spartina pectinata Bosc ex Link) is a common dominant species. Other grasses include big bluestem (Andropogon gerardii Vitman) and Indiangrass (Sorghastrum nutans (L.) Nash). Sedges are an important component, particularly in wetter areas. Several species are possible. The most noteworthy species are Bicknell’s sedge (Carex bicknellii Britton), woolly sedge (Carex pellita Muhl ex. Willd.), and Buxbaum’s sedge (Carex buxbaumii Whalenb.). Tussock-forming species like Hayden’s sedge (Carex haydenii Dewey) and upright sedge (Carex stricta Lam.) may be on site. Shrub cover is variable and includes leadplant (Amorpha canescens Pursh), willows (Salix L.) and dogwoods (Cornus L.), which quickly spread in the absence of frequent fire.
Today, high-quality, unplowed areas are extremely uncommon. Most remaining natural areas that are managed for tallgrass prairie were once tilled and utilized for agricultural production. It is therefore likely that 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. This is a stable plant community when grazing and fire are adequately managed. 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 wet-tolerant native grasses and a variety of native forbs. Frequent 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.
Resilience management. Prescribed fire and managed grazing are key resilience management practices.
Community 1.2
Old Growth Prairie
This plant community is characterized by a longer fire-free period than that of Community 1.1. Grass species are dominant, but more woody species are present due to the longer fire return times. Thatch and dead plant residue are denser than in Community 1.1.
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
A longer (greater than 3 years) is the primary factor controlling the transition from Community 1.1 and Community 1.2.
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 vegetative growth is reduced through burning.
State 2
Tillage State
Soil tillage is the primary mechanism affecting the transition to this state. Tillage affects dynamic soil properties such as bulk density, structure, organic carbon content, and saturated hydraulic conductivity. Hydrological modifications (tiling and ditching) are commonly installed to improve drainage, so natural hydrology is also altered. Most areas in this state will remain in use for crop production in the foreseeable future.
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, and protect water quality.
A small percentage of this ecological sites have been seeded to grass. Some previously tilled areas have been converted to warm-season grasslands under an NRCS conservation program. Species seeded will depend upon the hydrology of the site. Cool-season grasses are also feasible. The most common cool-season grasses are non-native species, such as reed canarygrass (Phalaris arunidinacea) and Kentucky bluegrass (Poa pratensis). Although cool-season grasslands are not biologically diverse, they still offer soil health and wildlife benefits.
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 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.
Resilience management. 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. Warm-season grasses are commonly planted through NRCS conservation programs. Also feasible are cool-season grass species such as reed canarygrass and Kentucky bluegrass. Many of these areas are eventually transitioned to annual crop production.
Resilience management. Resilience management practices include invasive plant management and a program of planned grazing. 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. Both warm-season or cool-season grasses are feasible for these sites. Species selection will depend upon specific site characteristics and landowner objectives.
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 pathway as areas are placed in crop production. The mechanisms of change are tillage and hydrological modifications.
State 3
Woodland State
In the absence of a natural fire or management, this site will transition toward the Wooded State. Disturbances such as unmanaged grazing, altered hydrology, and invasive species are often present. Vegetative composition and characteristics will vary depending on the age of the community and the type and severity of disturbances. Dominant tree species will vary, but commonly include eastern cottonwood, black willow, green ash, and boxelder. Reed canarygrass may be dense in open areas. Cool-season grasses such as Kentucky bluegrass and smooth brome may be present.
A small percentage of acres within MLRA 103 are in this State. Some remaining areas are conservation easements. Areas not in a conservation programs may be jurisdictional wetlands, making it very unlikely they will be transitioned to 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. Common trees include eastern cottonwood, willows, green ash, boxelder, and dogwood. Open areas may be dominated by reed canarygrass and other cool-season, non-native grasses. Plant community composition will be determined by past disturbances, seed sources, and the type and severity of current disturbances.
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. Resilience management practices include continual agricultural practices such as seeding, fertilizing, and managing invasive plants with herbicides or field cultivation.
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 resiliency of State 1.
Some tilled areas may be abandoned and return to woodland, but this is a small percentage of acres and not currently given a community in this model. Most acres converted to agriculture will stay as such for the foreseeable future.
Transition T1B
State 1 to 3
Plant community succession via the lack of natural fire and/or grazing. Brush and trees will increase and plant community structure will begin to move 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 hydrologic functions may be feasible to restore back to a reference community. Soil structure is intact and remnant plant communities may still exist on site.
Previously tilled sites (State 2) may revert to a woodland through abandonment; however, the soil function has been altered through tillage and intensive crop production. This site will not be the same ecologically as a true reference site.