Ecological dynamics
Marsh sites typically occurs on level or slightly concave landscape positions in closed depressions, shallow wetland basins, drainage ways; and adjacent to open water along lakeshore, ponds, and near streams. Soils are typically endosaturated, frequently ponded, and inundated with water for very long duration, at least 7 out of 12 months. Vegetation can be found rooting on floating mats (MNDNR 2003). Water sources include precipitation, surface flow, lateral flow, and groundwater discharge. The fluctuation of water levels on site are fairly stable (due to groundwater influences) and do not change seasonally, but can vary with drought or changes to drainage across the watershed.
State 1
Reference State
This state identifies the condition of Marsh prior to European settlement. Community phases within the Reference State are dependent upon ponding during the spring months. During drier times of the year, this site would burn regularly with the prairie fires that were common in the region. Woody species and upland grasses were kept from proliferating mainly by saturated conditions. The plants that dominate these community phases are adapted to long periods of inundation, having stems, leaves, and roots that diffuse oxygen from the air and store it in specialized cells (aerenchyma) (MN DNR 2003). Dominant species in this state include broadleaf cattail, river bulrush, softstem bulrush, giant bur-reed and water knotweed (Cowardin 2013).
While extensive acres of Marsh may still be found in MLRA 88, of those that still exist, it is likely that the hydrology has at least been slightly modified due to road development, tile drainage, ditching, and channelization elsewhere in the watershed(s), and invasion by exotic species is common (see State 2).
Community 1.1
Shallow Marsh
Cattails, bulrushes, and arrowheads establish in rising water levels, utilizing rhizomes, aerenchyma, and taller vegetation structures to remain established on-site as water levels rise. If water levels remain stable for a long period of time, this phase can lose diversity and may become comprised of only one or two species, usually cattail.
Community 1.2
Deep Marsh
As water levels rise and remain persistently high, floating species such as duckweeds and common white water lily become more frequent, as well as submerged species such as bladderworts, common coontail, and Canadian elodea (MN DNR 2003). In areas with more wave action, such as along stream beds or lakeshores, spikerushes, pondweeds, and watermilfoils may be more common (MN DNR 2003). Graminoids typically are found in patches, and can have variable cover across the site, interspersed by open water, and can include softstem bulrush, hard stem bulrush, river bulrush, slender bulrush, and Small’s spikerush (MN DNR 2003).
Dominant plant species
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softstem bulrush (Schoenoplectus tabernaemontani), grass
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hardstem bulrush (Schoenoplectus acutus), grass
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river bulrush (Bolboschoenus fluviatilis), grass
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slender bulrush (Schoenoplectus heterochaetus), grass
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dwarf spikerush (Eleocharis parvula), grass
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common duckweed (Lemna minor), other herbaceous
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common duckmeat (Spirodela polyrrhiza), other herbaceous
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Columbian watermeal (Wolffia columbiana), other herbaceous
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American white waterlily (Nymphaea odorata), other herbaceous
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coon's tail (Ceratophyllum demersum), other herbaceous
Community 1.3
Mud Flat
Water level drawdowns occur due to drought or diversion of water off-site due to beaver activity. Beggarticks and smartweeds germinate rapidly and prolifically on freshly exposed substrates and may find refuge on floating mats once water levels rise. Most of the submerged and floating species present in 1.2 are not resistant to desiccation and will disappear in this phase.
Dominant plant species
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beggarticks (Bidens), other herbaceous
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knotweed (Polygonum), other herbaceous
Pathway 1.1A
Community 1.1 to 1.2
Increased water depth and duration/excessive precipitation years which cause higher energy water and wave action.
Pathway 1.1B
Community 1.1 to 1.3
Little or no spring ponding/drought. One example of where this can occur is on the dry side of beaver dam construction.
Pathway 1.2A
Community 1.2 to 1.1
Decreased water depth and duration, cattail dominance which causes Lower energy water and wave action.
Pathway 1.2B
Community 1.2 to 1.3
Decreased water depth and duration; Little or no spring ponding/drought. One example of where this can occur is on the dry side of beaver dam construction. Also, potentially severe drought could create mudflats if the marsh is primarily fed by runoff/precipitation with limited groundwater inputs.
Pathway 1.3B
Community 1.3 to 1.1
Increased water depth that may potentially fluctuate in duration. It may occur with excessive precipitation years. This increased depth leads to an increase in cattails, bulrushes, and arrowheads. If the depth increases further this plant community will transition to a deep marsh plant community.
Pathway 1.3A
Community 1.3 to 1.2
Water levels rise and remain persistently high. Rapid increased water depth and duration/excessive precipitation years. This leads to cattails, bulrushes, and arrowheads having no chance to establish or they only may establish in patches. Floating species become more frequent, as well as submerged species (MN DNR 2003).
State 2
Invaded Marsh State
Sites in this state may be in set-aside conservation easements. Areas not in a conservation program are assumed to be jurisdictional wetlands, making it very unlikely they will be transitioned to the Cropland State 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 2.1
Degraded Marsh
Common reed is considered an invasive species, even though it has been present in North American wetlands for over 3,000 years, because its aggressive expansion, usually attributed to disturbances, has greatly increased over the last 50 years (Mitsch, 2015). The presence of invasive cattails or common reed is usually an indicator of altered hydrology and increases in salinity and nutrients. Burning and herbicide application are used for control. There are some desirable varieties of common reed, so managers need to be aware of the distinctions in haplotypes and how to identify them (Mitsch, 2015). Hybrid cattail and common reed have been more problematic in this region, in that they both have expanded more aggressively by replacing bulrushes and giant bur-reed as dominants (Eggers, 1997). narrow-leaved cattail tolerates more mixosaline and calcareous waters than broadleaf cattail. Narrow-leaved cattail tolerates higher levels of nutrient inputs, usually from agricultural runoff. Broad-leaved and narrow-leaved cattail freely hybridize to form the hybrid, Typha x glauca Gordon (Eggers, 1997).
Community 2.2
Wet Grassland
Disturbances such as artificial drainage, plowing, mechanized land-clearing, road construction, excessive sediment and/or nutrient inputs, allow reed canary grass to outcompete native plants and form monocultures, reducing diversity and ecosystem function. Shrubs can also invade in this phase of lowered water levels and altered hydrology.
Community 2.3
Loosetrife
Purple loosestrife has spread across much of North American marshes in the late 20th century, displacing literally every other native plant on-site, including Typha sp. (Mitsch 2015). It is often associated with wetlands that have been disturbed by agricultural use, drainage, pasturing, siltation, or water level fluctuations (Eggers, 1997). This is of great concern to managers, who care about the functions of the site for water quality and wildlife habitat, which is dependent upon a diversity of plant species present on-site.
Pathway 2.1A
Community 2.1 to 2.2
Drawdown of water levels due to water diversion or use throughout the watershed, partial drainage of the site due to ditching, or other impediments to water flow into the site
Pathway 2.1B
Community 2.1 to 2.3
Invasion of exotic purple loosestrife
Pathway 2.2A
Community 2.2 to 2.1
Increased water flow into site or ponding on site.
Pathway 2.2B
Community 2.2 to 2.3
Invasion of exotic purple loosestrife.
Pathway 2.3A
Community 2.3 to 2.1
Chemical (herbicide approved for use in wetlands), mechanical removal of purple loosestrife, use of biocontrol (loosestrife beetles).
Pathway 2.3B
Community 2.3 to 2.2
Chemical (herbicide approved for use in wetlands), mechanical removal of purple loosestrife, use of biocontrol (loosestrife beetles).
State 3
Cropland State
In the Cropland State, most ecological functions have been destroyed, converted, or otherwise removed from the system. In farmed conditions, dynamic soil properties such as bulk density, structure, organic carbon content and saturated hydraulic conductivity can change quickly because of various agricultural practices. Many of these sites are and will likely continue to be in corn and soybean production. There are certain management practices that are proven to be destructive, not only to the individual field, but to the watershed.
Dominant plant species
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corn (Zea mays), grass
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soybean (Glycine), other herbaceous
Community 3.1
Cropland State
Certain practices can mediate the destructive effect of traditional agricultural practices on the soil resource. Conservation tillage that minimizes soil disturbance is more sustainable than traditional methods. Corn and/or soybean plantings with a cover crop rotation can help to build soil structure, improve infiltration rates, reduce runoff and erosion and have a comparatively positive effect on the overall environment.
Dominant plant species
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corn (Zea mays), grass
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soybean (Glycine), other herbaceous
Transition T1A
State 1 to 2
Hydrologic alterations can, over time, transition the reference depressional marsh community into an invaded marsh state. A variety of invasive woody plants and grasses can become established and spread, shading out native species. Common non-native species that invade this state include narrowleaf cattail, hybrid cattail, reed canarygrass, common reed, purple loosestrife, and various small woody plants.
Transition T1B
State 1 to 3
To transition to the cropland state, subsurface tile drainage of the site must be utilized, as well as tillage, herbicide use, and seeding. Human driven hydrologic alterations can transition the reference depressional marsh state into a crop land state.
Restoration pathway R2A
State 2 to 1
Complete hydrologic restoration of wetland basin, invasive species management, seeding, muskrat re-establishment.
Transition T2A
State 2 to 3
To transition to the cropland state, subsurface tile drainage of the site must be utilized, as well as tillage, herbicide use, and seeding.
Restoration pathway R3A
State 3 to 1
Complete hydrologic restoration of wetland basin, invasive species mangement, seeting, muskrat re-establishment.
Restoration pathway T3A
State 3 to 2
From an abandoned Crop Production state, it may only take several years to transition to this state. This transition involves partial or complete hydrologic restoration of the wetland basin, and agricultural abandonment.
