Impact of Fire-Driven Forest Compositional Shifts on Evapotranspiration in Boreal North America
Tyler Albrethsen, University of Montana, tyler.albrethsen@mso.umt.edu (Presenter)
John S Kimball, University of Montana, john.kimball@mso.umt.edu
Arthur Endsley, University of Montana, arthur.endsley@ntsg.umt.edu
Wildfires are becoming more severe and frequent in North American boreal ecosystems, causing forest compositional shifts in black spruce-dominated landscapes. Between 1989 and 2014, approximately 38% of black spruce forests in North America affected by wildfire experienced compositional shifts to either jack pine or broadleaf dominated stands or failed to regenerate at all. These changes in vegetative composition have large implications for the hydrological regime, particularly for evapotranspiration (ET) which is the primary link between the terrestrial water and energy cycles. Climate projections indicate an intensification of the water cycle at higher latitudes, including an increase in ET. However, the trend is less clear in boreal landscapes due to large landscape heterogeneity. The complex effects of fire disturbance on forest composition represent a major potential factor in variations in ET trends across boreal systems. This proposed research aims to measure changes in ET across different fire severity regimes and assess the effects of fire-driven forest compositional shifts in boreal North America on actual ET. A driving premise of this study is that fire-caused compositional shifts from needleleaf to broadleaf dominated forests experience an increase in ET after recovery relative to unburned areas. To assess the effects of burn severity and vegetation shifts on ET, a Landsat-derived burn severity index will be applied to historical fire perimeters and upscaled to a coarser (500m) grid consistent with a long-term global satellite ET record. The ET estimates from MOD16 will be clipped to fire perimeters and compared to corresponding fire severity levels. ET estimates will also be taken at point locations of in situ post-fire regeneration data to understand how changes in ET relate to forest compositional shifts. With a better understanding of the link between fire severity and ET, estimates of trends in the water and energy cycles can be refined.
Associated Project(s):
Poster Location ID: 18
Presentation Type: Poster
Theme: Fire Disturbance