Restoration and Enhancement of Washington County's Public Lands

This project focused on restoration and enhancement of native plant communities in Washington County’s last best public lands, as identified by the DNR’s County Biological Survey, the Metro Conservation Corridors program, and the County’s Top 10 Priority Conservation Areas (January 2012). The goal of the project was to establish a 20% increase in species diversity, resulting in higher quality and higher functioning habitats. This was accomplished utilizing a combination of contractors and internal staff to complete buckthorn removal and follow-up on re-sprouts, native plant seeding, controlled burns and reducing dominance of reed canary grass in wetlands to increase available wildlife habitat. 

The restored and enhanced lands were selected strategically to connect existing managed native landscapes to previously isolated DNR identified rare and unique plant and animal communities. Ultimately, this has helped to create a mosaic of interconnected landscapes of sufficient size that will accommodate the greatest biological diversity.

Overall, Washington County restored or enhanced 284 acres of habitat, a 8% increase (21 acres) over the original project goal of 259 acres. Restoration and enhancement activities took place at three locations: along the St. Croix River (St. Croix Bluffs Regional Park), within a major watershed of the Mississippi River (Cottage Grove Ravine Regional Park), and within a wetland dotted landscape that is characteristic of east-central Minnesota and the St. Paul Baldwin Plains and Moraines landscape subsection (Lake Elmo Park Reserve).

Restoration focused on three habitat types: forest (154 acres), prairie (103 acres) and wetland (27 acres).

Summary of the restoration/enhancement efforts and the evaluation efforts in each habitat type:

Forest
Oak forest habitat enhancement was completed in all three locations in Washington County, for a total of 154 acres, including oak forest, mesic hardwood forest and oak savanna where undesirable shrubs such as common buckthorn have been out competing the native plant communities. In these areas, a contractor removed buckthorn and honeysuckle using a combination of forestry mowing, chainsaw cutting and stump treatments and basal barking. Material was either mulched on-site or piled and burned. Following initial removal, buckthorn and honeysuckle re-sprouts were treated with foliar chemical spray for two years following initial removal. 
In order to quantify the effectiveness of these approaches and the progress toward the goal of a 20% increase in species diversity, three plots were established at each location and surveyed each year from 2015 to 2018. The surveys showed that the work resulted in a significant decrease in buckthorn extent, height and density across all nine plots. As of 2018, Buckthorn extent was still below 25% in all but one plot, and below 10% in five plots. There was also an increase in native woody and herbaceous vegetation in all nine plots over the same time period. Native woody species increased from an average of 3.3 species/plot to 5.9 species/plot, and native herbaceous species increased from an average of 2.7 species/plot to 11.0 species/plot.  

Prairie
Stewardship work in the prairie included both 81 acres of enhancement and 25 acres of restoration at Lake Elmo Park Reserve. The tallgrass prairie enhancement was accomplished by interseeding native forbs into existing prairie restorations that were established in 1989. Prior to implementing, a pilot project was implemented to evaluate three different interseeding methods; the most successful method was determined to be a prairie burn, followed by discing and then broadcasting the forbs. A preliminary meandering survey of the prairie was used to identify species to interseed into the prairie and 51 forb species that were rare or absent were selected to be seeded in spring and winter of 2016. An average of 35% of the species seeded had established in a survey conducted in 2018, only 1-2 growing seasons post-interseeding. It is anticipated that more species will establish over time with continued management such as burning, grazing and or haying to reduce grass dominance.

In addition to the enhancement, 25 acres of prairie were restored from cropland, 11 acres using OHF funds and an additional 14 acres leveraged by the County. The seed mix included a mesic prairie mix used for 18.5 acres and a wet prairie mix for 1.5 acres. In total 86 different species were seeded by Washington County staff in the fall of 2015 using a Truax seed drill for grasses and broadcasting forbs. In a survey three years after planting, 51% of the seeded species were identified (44 species, 10 grasses/sedges and 34 forbs). Similar to the prairie enhancement, it is expected that species will continue to establish and be identified with more time and management. 

Wetland
27 acres of wetland, in 29 different wetlands, were enhanced at Lake Elmo Park Reserve, including seasonally flooded wetlands, mixed emergent marsh, wet meadow and littoral open water wetlands. A wetland management plan developed by Barr Engineering and Washington Conservation District detailed the control of reed canary grass as important to increasing wetland plant diversity. Enhancement methods included a combination of herbicide application and controlled burning, followed by seeding with a native wetland mix. Comparison of pre-enhancement and post-enhancement wetland surveys indicate an average reduction in Reed canary grass of 44%, as well as an increase in native dominant plant diversity in 22 of 29 wetlands surveyed (76%). Of the 43 species seeded by the contractors, 34 (79%) were identified in the 2018 post-enhancement survey. There are plans in place for continued follow-up on reed canary grass to ensure long-term persistence of the native plants.