6 Steps To Wetland Prairie Restoration
A successful wetland prairie restoration project involves a series of basic steps that should be followed to ensure the restoration site is appropriate and well understood and so that a diverse native ecosystem can be established and maintained over time. As is true with the management of any natural area, an adaptive management approach is recommended so that emerging threats can be identified and addressed. The six-step process listed below is recommended to ensure a successful wetland prairie restoration project.
Site SelectionSelecting a site that possesses appropriate soil types and hydrology along with consideration of the size and geographic context are critical evaluation factors for identifying sites that are likely to support a high quality wetland prairie ecosystem. Soils: Hydric soils must be present (NRCS classification for wetland soil types). Hydrology: Suitable wetland prairie hydrology should exist or have potential to be reestablished through removal of agricultural drainage features. Soils must be saturated or have shallow inundation during the wet season and become dry during the summer and early fall. Historic Condition: Evidence that the site supported a prairie ecosystem in the past should be established through interpretation of historic vegetation maps or historic aerial photos. Size: Wetland prairie restoration may occur on a site of any size, but larger sites tend to have higher potential for supporting a diverse native ecosystem and are less prone to invasion by non-native vegetation (lower edge to area ratio). Larger sites generally produce higher quality results, benefit from economies of scale, and are easier to manage over the long term. Proximity: Sites that are situated in close proximity to other natural areas or pro- vide critical connectivity are preferred. The Oregon Conservation Strategy (ODFW, 2006) and Willamette Synthesis Project (TNC, ongoing) provide direction toward selecting sites that provide strategic connectivity and support larger regional conservation goals.
Once a site has been selected, a thorough analysis should be conducted to gain a greater understanding of site attributes and to inform the planning and design process. Site analysis should include the following elements: Site History: Review of resources such as Site AnalysisGLO historic vegetation mapping, historic aerial photos (at right), agricultural records, and interviews of previous owners will help document the site history and provide explanation about current condition. Soils and Geomorphology: Provide an understanding of how the site’s geomorphic surface formed and the characteristics of the soils (based on NRCS mapping). Surface Hydrology: Determine and map the extent and depth of surface water and document flow patterns including artificial drainage feature. Understanding the site’s surface hydrology is important for selecting appropriate seed mixes, modifying drainage features if needed, and planning for erosion control during restoration. A typical Surface Hydrology Map for a wetland prairie site could include the following categories:Wetland Delineation: Determine the extent of the jurisdictional wetland. This is an important step if the site is being used for wetland mitigation or if earth-moving is planned (e.g. to reduce agricultural flattening) that may require permits. Otherwise, careful mapping of soil and hydrologic conditions may be suitable. Topography: Collect detailed topographic information to help interpret direction of flow, gradient, and whether there have been major modifications such as flattening or installation of drainage features. Vegetation: Document existing vegetation, including major invasive species populations. Non-native species may exist in the soil seed-bank, but be absent above-ground. Some practitioners recommend germinating soil samples during the planning period to better understand the full suite of non-native invasive species likely to emerge after existing dominant vegetation is removed. Surveys for rare plants may also be useful on some sites and may be required prior to issuance of state and federal permits. Wildlife: Record baseline wildlife data if feasible to help gauge long-term project success. This could include formal breeding bird surveys, reptile and amphibian surveys, or simple notation of wildlife observed during site visits. Context: Assess adjacent lands to help understand potential threats such as invasive species or changes to hydrology or potential opportunities such as proximity to other natural areas. Issues and Opportunities: Develop a comprehensive list of issues and opportunities that have been identified during the site analysis process. Issues and opportunities may relate to biotic and abiotic features, but may also relate to management issues such as site access or adjacent land uses, among others. Having these defined is very helpful for guiding the planning and design phase.
- Non-saturated soil (often not a wetland)
- Saturated soils, not inundated (no standing water above the soil surface)
- Inundated areas (up to 2 inches of standing water)
- Pools (2 to 6 inches of standing water)
- Persistent pools (>6 inches of standing water)
- Ditch or swale
- Direction of flow (for ditches, swales, and general direction of sheet flow)
The planning and design process should be collaborative and include a project coordinator and a technical team to provide input. The information gathered during the site analysis process (step 2) should be carefully considered by the team, including the list of issues and opportunities. The planning and design process should produce the following elements: Restoration Goals: Define the desired outcome of the restoration project and develop goals for habitat, hydrology, access, maintenance, and other key factors. Proposed Actions and Prescriptions: Develop proposed actions and restoration prescriptions to describe how the restoration goals will be met. This would include topics such as hydrologic modification, site preparation, invasive species control, seeding, and sequencing. Scheduling: It is typical for a project to span six years or more and it is critical to have a well-considered schedule in order to avoid missing key actions, which could set a project back a full year or more. Plant Materials Planning: Plant material can be one of the most limiting factors in successfully restoring biologically diverse plant communities. Early planning is valuable to ensure adequate seed collection, seed and plug/bulb grow out, and other plant material needs will be met when needed. Action Plan Map: Develop an Action Plan Map that depicts the desired future condition for the site including geographic extent of habitats, access, and other proposed actions. Monitoring Plan: Establish a set of monitoring goals, performance criteria, and quantitative monitoring objectives that can be used to gauge success. Categories typically include vegetation, hydrology, soils, and wildlife. Baseline Monitoring: Conduct baseline monitoring to document pre- project condition. Monitoring can include vegetation inventory, wildlife surveys, and establishment of photo points. Permitting: Prior to any significant site modification, applicable state and federal permits should be obtained including Removal-Fill permits. The Planning and DesignOregon Department of State Lands or Washington Department of Ecology are both good starting points for the most up to date permitting requirements.
The process of preparing the site for the eventual establishment of native vegetation typically includes the following: Hydrologic Modification: Complete hydrologic modifications such as ditch removal, installation of water control structures, or incorporation of hydrologic variation such as vernal pools or shallow swales if desired. In some cases this can also include removing fill piles or smoothing or removing spoils from ditch digging. Access: Identify temporary and permanent access points, staging areas, and access routes and install proposed access controls to prevent trespass (fences and/or gates as needed). Vegetation: Eradicate existing non-native vegetation and the associated seed-bank. This typically involves multiple treatments over an extended period of time. Site Preparation
A detailed description of Site Preparation Techniques and Recommended Approaches can be found in Chapter 4 of the guide (see left sidebar for link).
Following successful site preparation, the beginning of a diverse native wetland prairie plant community is established, typically over a two to three year period. Seed and Plant: Seed and plant native wet prairie species based on site goals, hydrologic conditions, and expected control needs for non-native invasive species. Specific planting strategies, which incorporate the microsite variation found across a site, will have the greatest chance of success. If starting with an agricultural wetland, typically emphasize forbs and hard-to-establish grasses, sedges, and rushes during the first two years, adding more competitive grasses in year three, once other species are better established. This strategy is often chosen in situations where non-native grasses are the dominant pre-restoration vegetation or the last farmed crop, because a soil seed bank of invasive grasses will exist, requiring control of these species for several years. Assess and Adjust: Annually assess the establishment of the species seeded in prior years and the emergence and density of non-native species, and adjust native seeding rates, planting palettes, planting locations, and species composition to achieve diversity, cover, and wildlife goals. Plant Establishment
A detailed description of Plant Establishment Techniques and Recommended Approaches can be found in Chapter 5 of the guide (see left sidebar for link).
A management strategy should address how to guide the developing native wetland prairie community toward a state of persistence and resilience. Wetland prairies will require management in perpetuity to maintain species diversity, control invasive species. Apply timely disturbances (e.g. fire, mowing) and other actions to maintain structural and functional goals. Monitoring: Successful long-term management depends on a system to assess success in controlling invasive non-native species, achieving desired site hydrology and controlling erosion, maintaining diverse plant and animal communities, and managing site access, if needed. Adaptive Management: Management strategies should be adapted based on the results of formal or informal assessments. New strategies should be considered where persistent problems occur. Some management tools that are applied only every few years, such as use of controlled ecological burns, will require longer time periods over which to judge success and may require periodic increases in management investment, for instance if they temporarily increase the vulnerability of the restored community to invasion by non-natives. Long Term Management
A detailed description of Long Term Management Techniques and Recommended Approaches can be found in Chapter 6 in the guide (see left sidebar for link).