Wetland Restoration and Management

Wetland management is done to maintain wetlands in an early successional state.  Repeated, periodic disturbance of the vegetation and soil creates quality habitat for migratory birds, in particular waterfowl, shorebirds, whooping cranes and piping plovers.  The disturbance allows early successional plant species such as smartweeds  and wild millet/barnyard grass to prosper.  It also reduces competition enough to allow desirable species such as rice cutgrass, spikerushes, burreed, beggarticks, the dominant sedges, and others to become established where species such as reed canarygrass, river bulrush, and/or cattail once formed monotypic stands--caused by no disturbance.

Many "desirable" species are annual plants that reproduce from seed or are short-lived perennials with heavy seed production. Species such as wild millet and smartweed have been documented to produce more than 1,000 lbs. of seed/acre (Maury Lauban, Waterfowl Management Handbook). Desirable species have lower lignin and woody fiber content, support higher aquatic invertebrate populations, and typically die back and decompose more quickly after frost than river bulrush, reed canary grass, and cattails. All of these traits are highly desirable when the goal is providing fall/spring migratory habitat. The increased seed production and aquatic invertebrate populations provide necessary food and important nutritional elements in the diet. The open-water habitat provided in the fall and spring are significantly more attractive to most species of waterfowl and shorebirds.

Undesirable plants, primarily reed canary grass, river bulrush, and cattail, create a thick organic layer on the soil surface if left undisturbed. The thick layer soaks up a large amount of surface water runoff. The result is less open, shallow water for migratory birds, and cool, moist soil that discourages desirable plants. Dense stands of undesirable plants also have high evaporation-transpiration rates, negatively affecting the basin's hydrology and plant diversity. Water budgets for cattails in some regions have been estimated to exceed 36 inches per year.

The hydrology in nearly all of the wetlands has been significantly altered. A combination of road ditches and pits provide a 1-2 punch to divert water, allow for agricultural use of the surface water, concentrate water into pits, and breach the impermeable clay layer that lies under the wetlands. In order to maintain quality habitat, we pump ground water into wetlands to compensate for the loss of surface runoff. Past experience has shown that pumping into wetlands dominated by river bulrush or reed canarygrass is costly and receives relatively little use by migratory birds.

Research conducted of wetland habitats indicates that most species of ducks, geese, and shorebirds prefer water that is only inches deep. Ideally, wetlands would have water levels from one foot deep grading to zero inches with a large part of the basin 6 inches or less during the peak of the migration. Trying to accomplish this with a thick humus layer (12 inches or more) of river bulrush and/or reed canarygrass is difficult and require us to pump large amounts of water before it begins to show above the organic layer. Even then, the birds have to work through the standing vegetation to get to the water. Once there, the birds find few food resources such as seeds and aquatic invertebrates available. This is obvious to the casual observer during migration simply by examining what areas the birds select and is verified repeatedly with research.

Many factors influence plant response after a disturbance, including time of year, intensity of disturbance, length of disturbance, precipitation (frequency, amount, and timing), and diversity and abundance of seeds in the soil. One thing is certain however, most of the wetlands in the Rainwater Basin will eventually become dominated by either river bulrush, reed canarygrass, cattails or volunteer trees if left undisturbed.

Wetland managers believe that disturbance in the Basin was historically widespread and frequent. The most common disturbance included wildfires and grazing bison. Wildfires typically occurred during late summer to fall and in late winter to early spring. The fires exposed the wetlands to additional drying and left them unprotected from wind erosion associated with severe northerly winds in February and March. Bison herds used the wetlands as their source of water and caused a tremendous impact on aquatic plants and the soil surface (trampling effect).

Today, the more common natural disturbance events include drought, dramatic flooding events, wind erosion (when mud flats are exposed and dried), and intense grazing by large concentrations of snow geese.

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