Science You Can Use Bulletin: Slash from the past: Rehabilitating pile burn scars

In the National Forests of northern Colorado, there is a backlog of over 140,000 slash piles slated to be burned, most of them coming from post-mountain pine beetle salvage logging and hazard reduction treatments. Burning slash piles can create openings in the forest that remain treeless for over 50 years, and can also have the short-term impacts of increasing nutrient availability and creating opportunities for weed establishment. Working with managers, RMRS researchers have evaluated the available treatments for short-term rehabilitation of both smaller, hand-built and larger, machine-built burn piles. For the smaller piles, they found that both soil nitrogen and plant cover recovered to a level similar to that of the surrounding forest within two years, indicating that these scars may not need rehabilitation unless in a sensitive area. Seeding with native mountain brome (Bromus marginatus) was an effective option for the larger piles, whereas mechanical treatment either alone or with seeding did not increase plant cover. The root causes behind the long-term lack of trees are not yet clear, and the next step is to conduct field and lab studies to evaluate whether soil factors, competition with grasses, and/or herbivory are possible explanations.