RAPID: Collaborative Research: The 2016 Yellowstone Fires: early indicators of ecosystem transitions in a changing fire regime.

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Forests in the western US are facing warmer temperatures and larger, more severe wildfires than at any time in recorded history. Lodgepole pine forests of Yellowstone National Park (Wyoming) are well adapted to large, severe wildfires, which have burned at 100 to 300-yr intervals during the past 10,000 years. However, the interval between fires is shortening, making it likely that young forests will re-burn before fully recovering from previous fires. How forests will respond to more frequent fire and warmer, drier conditions is not known. Wildfires during summer 2016 burned young forests (less than 30 years old) that grew after the momentous 1988 Yellowstone Fires. These recent fires produced an unexpected opportunity to study the characteristics of short-interval fires and their effects on western pine forests. Sampling soon after severe fire is necessary because the time to find field evidence of burn severity is very short after the fire, and most tree seedlings establish during the first year after the fire. This RAPID award will measure burn severity, tree establishment and carbon storage in young forests that burned in 2016. Results will be immediately useful to regional forest managers, and mini-documentary videos will explain effects of increasing fire activity on western forests to a wide audience. Field data also will be used to improve computer models of forest growth and to assess burn-severity patterns across the US northern Rocky Mountains. Field studies in areas burned in the 1988 fires that burned again in 2106 will test three hypotheses. (1) Short-interval fires will reduce forest resilience because burns will be of high severity, and post-fire conifer regeneration and carbon storage will be substantially reduced. (2) Post-fire climate will amplify consequences of short fire-return intervals such that post-fire conifer establishment will be substantially reduced (or fail) in re-burns where conditions are warm and dry. (3) Regionally, the proportion of high-severity fire will be greater in short-interval than long-interval fires, but landscape patterns of high-severity fire will be similar. Burn severity, tree regeneration and carbon storage will be measured during summer 2017 in 0.25-ha plots following standard protocols. A seed addition experiment will be conducted to separate effects of seed supply from post-fire climate conditions on tree seedling establishment. Plot-based burn-severity data will be used to validate satellite-based burn-severity metrics and to map spatial patterns of burn severity in short-interval fires across the Northern Rockies. This study will help scientists and managers understand conditions likely to change forest ecosystems fundamentally in a future with more fire.