Depressional Marsh

Description

The Depressional Marsh ecological site is characterized by a native, hydrophytic plant community that was historically influenced by drought, fire, and grazing. Plant community structure and composition will vary on this site depending on hydrology. Dominant species include broadleaf cattail (Typha latifolia) and river bulrush (Bolboschoenus fluviatilis). Increases in water depth favor softstem bulrush (Schoenoplectus tabernaemontani) and giant bur-reed (Sparganium eurycarpum). Water knotweed (Polygonum amphibium) is common on muddy flats during drier periods.

High-quality, natural reference sites are now uncommon in MLRA 103. Most sites have been transitioned to agricultural production. Of the sites that still remain, many have altered hydrology due to adjacent tile drainage and ditching.

Submodel

Description

The Degraded Marsh State is characterized by one or more disturbance triggers. These disturbances could be hydrology alterations, non-native plants species, cattle grazing, or long-term fire suppression which allows for an increase woody plant species. Common species include common reed (Phragmites australis), narrowleaf cattail (Typha angustifolia), hybrid cattail (Typha ×glauca), reed canarygrass (Phalaris arundinacea), and various shrubs and tree saplings. Plant community composition will be influenced by the type, severity, and duration of disturbances as well as the depth of ponding.

Some areas in State 2 may be in a conservation easement. Areas not in a conservation program are assumed to be jurisdictional wetlands, making it very unlikely they will be transitioned to agriculture 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).

Submodel

Description

Tillage and drainage are the primary mechanisms for transitioning to this state. Most of these sites were transitioned to agriculture prior to current wetland protection legislation.

Soil tillage affects dynamic soil properties such as bulk density, structure, organic carbon content, and saturated hydraulic conductivity. Hydrological modifications (tiling and ditching) may be installed to improve drainage, so natural hydrology is also altered. Most areas in this state will remain in crop production in the foreseeable future – primarily in an intensive corn and soybean rotation. Conservation 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 erosion, and protect water quality.

Some areas may be seeded to grass or have reverted to a scrubby woodland. However, this is a small percentage of acres within the MLRA, so these communities are not currently included in the state and transition model.

Resilience management

The mechanisms of change are tillage, drainage, and intentional plant establishment (crop seeding). Resilience management practices include weed control (herbicide application), field cultivation, fertilizer application, and harvest management.

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