• Start-up
  • Planning
  • Action
  • Evaluation
Bohn Farms was predominantly agricultural lands, farmed for over one hundred years. The Wisconsin DNR In Lieu Fee Wetland Mitigation Program worked with wetland consultants from Stantec to develop a ten-year wetland restoration plan for Bohn Farms that incorporates climate change adaptation into project plans. This site has features that may position it to cope with climate change, including: location on a sub-watershed divide, with almost no inflow of surface water runoff; location near northern limits of many species ranges; extensive adjacent conservation lands and managed habitats. The eastern portion of the site has an interesting mosaic of remnant upland and wetland habitats.

Project Area

Field to the east (photo: Josh Sulman)
The Bohn Farms property (80 acres) was previously under longtime ownership by a family farm and used for agriculture - ranging from pasture to intensive row crop cultivation. Surrounding the site, the adjacent land uses include residential development, agriculture, and conserved lands. In 2018 the Wisconsin DNR acquired the property.
The site has rolling lake plain topography, with pronounced microtopography in eastern one-third of site, providing a mosaic of ephemeral wetlands and upland forest. Most of the site is composed of heavy clay soils formed as lake sediments, with localized areas of sand formed as beach ridges. For decades the western two-thirds of the site has been tilled and drained through an extensive network of ditches. Vegetation on these portions of the site is largely dominated by annual weeds. The eastern third of the site contains remnant grassland and forested communities, and ephemeral pond wetlands. Wetlands onsite consist of degraded wet meadows (farmed wetland), forested wetland, ephemeral pond, and degraded wet prairie/sedge meadow. Restoration of the site will enhance and restore natural communities on site, such as open wetlands (wet prairie and sedge meadow), oak savanna, and prairie. Unique to this site are ephemeral ponds which are significant habitats for amphibians and other wildlife, and are considered vulnerable to climate change.

Management Goals

Ephemeral ponds (photo: Josh Sulman)

The Wisconsin DNR Mitigation program’s goal is to manage Bohn Farm as a healthy wetland, that provides diverse wildlife habitat and natural communities, and will restore wetland functions that have been lost within the watershed. To help achieve this long-term management goal, the Wisconsin DNR Mitigation program and Stantec are planning to restore ecosystem and hydrologic function of the site, and create a wetland mitigation plan to guide implementation and establish performance meaures for the site that will be monitored over the next five to ten years.

The following are objectives for the restoration of Bohn Farms:

  • Restore upland portions of the site to a variety of high quality natural communities including oak savanna, dry-mesic prairie and mesic prairie.
  • Restore drained/altered crop lands and old pasture to diverse native herbaceous wetland communities. To meet mitigation site requirements, this includes restoring wetland vegetation and hydrology to 35 acres of hydric soils where wetlands were lost through past land use.
  • Provide slow release of clean water to downstream watershed, and increase storage capacity for stormwater.
  • Increase grassland/wetland wildlife habitat (birds, herps, pollinators).
  • Control invasive species including reed canary grass (Phalaris arundinacea), invasive Phragmites (Phragmites australis subsp. australis), non-native cat-tails (Typha angustifolia, T. X glauca), common buckthorn (Rhamnus cathartica).

Climate Change Impacts

For this project, the most important anticipated climate change impacts include:
Precipitation projections point to increases in annual precipitation, potential for reduced growing season precipitation, and continued increases in intense precipitation events.
Increasing winter and spring precipitation, that may result in lower snowpack and less infiltration. Rain in winter and spring increases risks of erosion, can affect early stages of vegetation establishment.
Dry and droughty conditions may affect plant establishment, especially on clay soils. Reduced soil moisture is of concern in mid-elevations, and in formerly cropped areas with compromised structure and less organic matter.
Ephemeral ponds are vulnerable to changes in water depth, and warming temperatures.
Invasive species are expected to get worse over time. Non-native invasive species and woody species may outcompete vegetation, particularly early prairie plantings. Reed canary, invasive Phragmites are already on site, and hybrid cat-tail exist nearby.
Prominent upland forest and savanna species onsite, including white, bur, and swamp white oaks, are projected to have suitable habitat on site by end of century.

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Increased competition and spread from invasives, particularly during establishment phase.
Heavy rainfalls could wash away seed, injure/uproot plants during vulnerable life stages, or reintroduce invasive propagules.
Sedge meadow species and hummock microtopography may be vulnerable to sedimentation.
Drought could wipe out young plantings.
Clearing trees for restoration may increase risks to grown oaks and increase vulnerability to wind damage.
Canopy openings may have negative impacts on ephemeral ponds by increasing water temperatures and changing how ponds receive precipitation, affecting amphibian breeding.
Brush invasion may become a challenge to maintaining herbaceous species diversity in forest and savanna groundlayers, prairie, and herbaceous wetlands; atmospheric nutrient enrichment may increase woody vigor and growth rates.
Enhanced invasive species vigor due to longer growing seasons may become difficult to control, and existing control measures (e.g. herbicide application) may conflict with native plant establishment.
Windows of opportunities for prescribed burns could change (e.g. smaller burn windows), a control measure critical to managing reed canary grass and brush invasion.
There is uncertainty about future precipitation and hydrological conditions that may conflict with restoration project specifications.
Extreme rain events and frequent inundation could erode or overwhelm water control features (e.g. berms).

Opportunities

The site is located in the Tension Zone, near northern range limits of many species; offers flexibility for using a range of prairie and savanna species that are likely to migrate north.
Increased opportunities for including more southern species in planting mixes. Wet prairies and sedge meadows are inherently adaptable to variable hydrology; this is the mechanism behind hummock formation. Longer growing seasons can help establishment.
Prairie species are intrinsically heat- and drought-tolerant. Wet prairie species will be more flexible to accommodate fluctuating water levels, and drought.
Existing elevation variations promote overall diversity and can allow the site to accommodate variable precipitation and hydrology.
If climate change promotes greater growth of prairie and wetland plants, the resulting biomass and thatch, may help fuel fires.
Opportunity to increase water storage capacity for stormwater due to amenable site conditions, earthmoving equipment, budget.
Mature oaks (swamp white and bur) on sites are drought tolerant and can tolerate upland and wetland conditions, offering flexibility with changeable moisture regimes. Oaks are expected to have more suitable habitat in the future.

Adaptation Actions

Project participants used the Adaptation Workbook to develop several adaptation actions for this project, including:

Area/Topic
Approach
Tactics
Entire site
Monitor sites that are vulnerable to invasive species invasions (e.g., areas prone to flooding); and control new infestations before they become dense.
Conduct prescribed burns to restore savanna and wetland communities.
Open Wetlands (wet prairie and sedge meadow
Plant a large number of diverse species that can tolerate a broad range of moisture regimes (including inundation and drought) and clay-tolerant.
Seed species broadly across edaphic gradients to allow plants to occupy spaces according to moisture and nutrient tolerances.
Implement passive hydrological control by designing small check dams/ditch plugs to retain water on site.
Design perimeter berms to withstand extreme storm events and retain water on site.
Examine adjacent off-site water levels and flow patterns during extreme rain events to determine if there is potential for invasion by invasive species (e.g. Typha, etc.).
Wet Mesic Oak Savanna
Retain shading around ephemeral ponds and target clearing in the subcanopy and less clearing in the canopy layers, retain mature oak trees.

Monitoring

Project participants identified several monitoring items that could help inform future management, including:
Invasive species: Annual meander surveys and quadrat surveys (species and percent cover, if >20% cover implement control measures)
Acres of wetland: Following 5 year delineation (total acreage of wetland onsite will be delineated, and compared to baseline delineated acreage, prior to construction--2018)
Prescribed burn implementation: Post burn inspection - acres burned, percent black, percent cover of native vs. invasive/wood plants, grassland birds
Shallow groundwater hydrology: monitoring wells across Site wetlands will record water table data for the first 3—5 years following construction

Learn More

To learn more about this project, contact
Danielle
.

Keywords

Water resources
Wetlands

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