Location
States
VermontEcosystem
Forest, River/streamIntroduction
Riparian ecosystems provide many important ecosystem services including streambank stabilization, sediment retention, flood mitigation, temperature moderation and habitat for many native fish and wildlife species. Historically, riparian riparian
Definition of riparian habitat or riparian areas.
Learn more about riparian ecosystems were degraded from the conversion of riparian forests to agriculture. This is the case in northern Vermont, where riparian areas along streams and rivers were converted to corn fields, hay fields, and pasture which are often dominated by reed canary grass (Phalaris arundinacea).
In northern Vermont, the Vermont Fish and Wildlife Department (VFWD), Connecticut River Conservancy (CRC), and the U.S. Fish and Wildlife Service (USFWS) are utilizing nature-based solutions to restore and create riparian buffers to improve habitat for native fish and wildlife, strengthen streambanks, and retain sediment and decrease nutrient loading from agricultural runoff. Riparian restoration can mitigate the adverse ecological effects from deforestation, moderate temperature fluctuations in streams for native aquatic species, and increase diversity and heterogeneity of riverine and riparian plant and animal communities.
To further research riparian restoration methods, the VFWD and CRC conducted a floodplain restoration experiment in the Willoughby Falls Wildlife Management Area (WMA), with later involvement of the USFWS. Willoughby Falls WMA is a 610-acre parcel consisting of floodplain forest, wetland ecosystems, and former agricultural lands along the Willoughby and Barton Rivers in the Lake Memphremagog watershed. At Willoughby Falls WMA, the partners are working to restore riparian areas from dense, non-native hay fields to native floodplain forests. Previous attempts at restoration had failed at Willoughby Falls WMA. However, this area provided an opportunity to conduct an experiment on non-native vegetation control techniques that might encourage re-establishment of native trees and shrubs.
Key Issues Addressed
Human interference with floodplain forests and rivers has decreased streambank support, reduced water filtration, increased loss and degradation of fish and wildlife habitat, and exacerbated erosion in northern Vermont. Riparian areas were cleared of native vegetation and re-planted with reed canary grass to support hay production and livestock grazing. Additional invasive plants, including field bindweed (Convolvulus arvensis)and wild parsnip (Cicuta maculata), have also become more prevalent. Channelization of the river allows water to move at much greater rates than historical settings, increasing erosion. Furthermore, removal of species such as box elder (Acer negundo) and silver maple (Acer saccharinum), among others, has also led to decreased streambank stability and decreased the function of riparian areas as important fish and wildlife habitat and as , which filter agricultural runoff and reduce nutrient and sediment loading. Such degradation has also resulted in the loss of Vermont鈥檚 most important wildlife corridors and left remaining native fish and wildlife populations increasingly vulnerable. Less tree cover results in warmer and more dramatic variation in water temperature, which can prove harmful to many native fish populations.
Vermont鈥檚 winters also create challenges for the saplings and seedlings necessary for floodplain forest regeneration. Rivers in northern Vermont experience freezes, where ice forms a solid cover that is then broken in spring. During winter and spring flood events, large pieces of ice ranging from 5 to 10 feet across can shear young saplings and wipe out planted trees and shrubs. These ice flows can also cause significant flooding and erosion.
Increasing white-tailed deer (Odocoileus virginianus) populations further hinder restoration efforts by decreasing the available seeds in the soil and heavily browsing young seedlings and saplings. Small mammals, such as moles and voles, and American beaver (Castor canadensis) can similarly cause mortality of planted trees during restoration efforts.
Project Goals
鈥淐ornfield Replication Experiment鈥� The experiment attempted to mimic conditions in plowed cropland that allow germination of native riparian tree seeds.
- Conduct an experiment to determine best methods for re-establishing floodplain forests and restore ecosystem health and services in areas currently invaded by reed canary grass
- Remove non-native vegetation and create bare earth soils for native tree germination and establishment through plowing and herbicide treatments
- Collect data to allow application of results to large-scale restoration efforts and development of future research, including direct seeding trials
Project Highlights
- Experimental Design: The CRC and VFWD chose two former hay fields in the Willoughby Falls WMA that had dense, non-native grass species and high rates of bank erosion to conduct a riparian restoration experiment. Each field had six blocks that contained four 5 meter by 30 meter plots. Those plots received one of four treatments: Control, Plow Only, Plow Then Herbicide, Herbicide Then Plow.
- Real-World Conditions: To overwhelm white-tailed deer herbivory and small mammals browsing impacts, treatments were implemented to encourage high-density seedling establishment. The investigators purposely chose to conduct the experiment in a less-controlled environment to match natural stressors the vegetation would experience, such as wildlife herbivory or ice flow damage during spring flooding.
- Measuring Woody Plant Success: Using transects within each plot, researchers measured bare soil and plant cover (including native forbs) for 3 years. Woody plant generation was quantified in circular plots within the transects that were separated at least 5 m. Data collected in 2019 included reed canary grass and field bindweed ground cover percentage, along with the stem heights of the ten tallest individuals within each species.
Lessons Learned
A plow then herbicide treatment best encourages the regeneration of woody plant seedlings. Plots with this treatment had the greatest decrease in grass cover, high average forb cover, highest density and height of seedlings, and highest growth rates. Plow then herbicide plots had an average of 36,757 seedlings per hectare in June 2018. The density of seedlings has declined over time to 17,938 per hectare in June 2020. Plots that were sprayed with herbicide, plowed, and planted with non-native turnips (Brassica rapa ssp. rapa), an annual cover crop, further supported the plow then herbicide treatment. The turnip plot had the tallest tree seedling height averaging 44 cm tall in June of 2019, and were mostly covered with forbs due to their complete cover of bare soil and little plant litter.
The use of the Rodeo-label glyphosate herbicide was met with resistance from collaborating partners. Its environmental concerns in combination with the other proposed activities left both public and private landowners reluctant to support the experiment. Strong communication and data showing that herbicide amplifies the efficacy of mechanical treatments has alleviated criticism on herbicide use. Additionally, the project land was agricultural land, leading to some resistance from the Department of Agriculture, nearby towns, and land trusts who were needed for permits and approvals. Prioritizing agricultural acreage that has historically been difficult to manage (made farmable by diverting or draining water) can create financial incentives and political will for fields to be taken out of production and made them available for restoration.
Understanding timing and locality is important. Originally, herbicide was applied early in the year, but these conditions did not match natural reproduction of woody species in Vermont. Late summer and fall are the optimal times for seed bed preparation. Creating bare earth conditions late in the growing season inhibits regeneration of invasive species invasive species
An invasive species is any plant or animal that has spread or been introduced into a new area where they are, or could, cause harm to the environment, economy, or human, animal, or plant health. Their unwelcome presence can destroy ecosystems and cost millions of dollars.
Learn more about invasive species and provides bare earth beds to allow germination of both fall and spring seedings. Knowing when other invasive species would seed sites can help with experimental designing, such as planning plot distances and timing of bed preparation events. Farmers can also offer input on best practices for restoration because they have learned how to combat reed canary grass and other species that inhibit regeneration of woody stems when planting corn.
This experiment provides the foundation for future riparian restoration of areas with dense invasive grasses. Work is underway to determine if invasive grass treatment followed by direct seed application of floodplain tree species will improve project success. This combination of techniques may increase the density of tree seedlings sufficiently to overcome natural mortality resulting from flooding, ice flows and herbivory by wildlife.
Next Steps
- Continue monitoring experimental sites in Willoughby Falls WMA
- Apply methods developed through this experiment to other field sites in the Northeast in collaboration with the U.S. Fish and Wildlife Service, including a project to test the benefits of direct seeding to augment natural seed rain on bare earth soils
- Test additional restoration methods on additional degraded riparian sites that are dominated by invasive plant species
- Communicate successful restoration techniques from experimental projects to a wider audience to expand funding opportunities for large-scale implementation of new restoration techniques
Funding Partners
- Vermont Hunting License Sales and Pittman-Robertson Funds
Resources
- Beck Pond LLC
Contacts
- Fritz Gerhardt, Conservation Scientist, Connecticut River Conservancy: [email protected]
- Peter Emerson, Fisheries Biologist, Vermont Fish and Wildlife Department: [email protected]
- Annalise Carington, Conservation Specialist, USFWS/Intervale Center: [email protected]
CART Lead Authors
- Madison Bigham and Nicole Williams, CART Student Writers, University of Arizona
Suggested Citation
Bigham, M., and Williams, N. (2021). 鈥淩iparian Restoration Experiment for Native Species Conservation in Vermont.鈥� CART. Retrieved from /project/riparian-restoration-experiment-vermont.
