Crack willow trees in the landscape. Credit: Robert Vidéki, Doronicum Kft., Bugwood.org, CC BY-NC 3.0 US, cropped for use.
Background
Invasive crack willow trees are found along many streams in the Duluth area and throughout Minnesota. These large trees shade the rivers, potentially providing benefits to coldwater species like brook trout, but they also impact the channel by creating root dams and debris dams that trap sediment and change aquatic habitats.
Very little research has been conducted on the impacts of crack willow on streams in North America, with essentially no research done in the Upper Midwest or Great Lakes regions, despite an abundance of crack willow present. There is a need to fill data gaps on the impacts of riparian crack willow on stream geomorphology and physical habitat.
Research questions
- How does crack willow impact stream shading and temperature?
- What are the leaf litter inputs?
- How does it affect stream geomorphology and aquatic habitats?
- What management strategy best reduces negative impacts to streams while preserving the benefits of shade?
Practical implications
This project is the first study of crack willow impacts on streams in the Upper Midwest or Great Lakes regions and will complement the work in a parallel investigation. The findings will help land managers understand the positive and negative impacts of crack willow on Duluth-area streams. This can lead to making informed decisions about whether or how to manage this species.
Findings
This project began in January 2026 and is in progress for the next several years. Please check back at a later time for updates.
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