Seedlings of native species on a forest floor, part of a revegetation effort after invasive species removal. Credit: Domini Brown
Background
Ongoing losses in native biodiversity and concurrent ecological disturbances have left Minnesota’s forests increasingly vulnerable to invasion by exotic plant species such as buckthorn, honeysuckles, garlic mustard, and others. Through the MITPPC-funded Cover It Up! project, researchers have shown that seeding and planting native species can greatly improve the efficacy of invasive plant removals, and may be able to fortify forests against invasion and improve forest health. These insights have meaningfully impacted the potential scope of forest management in Minnesota and beyond, but it is unclear how well these approaches work for honeysuckles and garlic mustard, which invade many of the same habitats as buckthorn, or in the context of novel environments created by oak wilt and chronic wasting disease (CWD).
Oak wilt and CWD are changing Minnesota’s forests in ways that present new challenges and opportunities for invasive plant management. Oak wilt is a highly contagious and lethal fungal pathogen that creates spreading patches of dead oaks and increasingly large canopy gaps. Although these gaps may normally promote canopy regeneration from smaller oaks, these gaps more typically promote the success of garlic mustard, buckthorn, and honeysuckles that use increased light to grow faster and larger since native plants are suppressed by the combined pressures of competition from invasive plants and intense herbivory from white-tailed deer (Odocoileus virginianus). However, pressure from deer is likely to change as CWD continues to spread throughout the state. CWD is a condition affecting deer wherein malformed proteins rapidly degenerate nervous tissues and eventually kill the animal, and reductions in deer populations caused by CWD may facilitate the successful establishment of some previously-excluded native species.
Research questions
- Can herbaceous revegetation suppress invasion into canopy gaps created by oak wilt?
- Can selective tree planting be used in combination with herbaceous revegetation to simultaneously regenerate canopy cover?
- How do declining deer populations associated with CWD affect the invasion potential of buckthorn and the ability of managers to establish buckthorn-suppressing cover?
Practical implications
By identifying a wider set of conditions within which revegetation can be effectively used, this work will reduce invasion and limit the amount of herbicides and other interventions needed to improve forest health, ultimately allowing managers to do more with limited time and funding.
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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