Post-harvest slash burning in coniferous forests in North America: A review of ecological impacts

Increasing drought and changing temperatures drive researchers to seek more efficient and effective means to aid management of coniferous forests across the western United States. Thinning allows for effective removal of biomass, but with few options to remove the residual slash from the treatment unit after saleable timber is taken away, pile burning has become a favored method of debris removal. Pile burning has greater efficiency and reduced removal cost as compared to air curtain burning or whole tree removal. In this review, we synthesize the current knowledge on the effects of slash pile burning on soil physical properties, soil nutrients, impacts to understory vegetation and tree regeneration, animal responses to pile burning, and the variety of remediation techniques for burn scar areas. Forest composition and age, climate, and fire intensity have the greatest impact on the outcomes of pile burning. Pre-fire ecosystem dynamics influence the changes to soil structure and nutrient profile, where native vegetation can either capitalize on changes such as altered nitrogen pathways, or be outcompeted by nonnative species. We hypothesize that vegetation adaptations to the natural fire interval may play a role in recovery from these high-intensity burn piles, and with further research, could assist managers in improved remediation efforts. We identify existing gaps in our knowledge of the ecosystem effects of slash pile burning, and to suggest some management-centered areas for further research.