Drought impacts on forest biomass mortality from fires and insects across the western United States during recent decades

Logan Travis Berner, Oregon State University (OSU), logan.berner@oregonstate.edu (Presenter)
Beverly Elizabeth Law, Oregon State University (OSU), bev.law@oregonstate.edu

Rising temperatures and declining mountain snowpack are increasing drought-stress across many forests in the western United States. Increasing drought-stress is coincident with a rise in forest disturbance by fires and insects. We are examining the carbon implications of forest disturbance by fires and insects across this region during recent decades, as well as the role of drought in shaping patterns of disturbance. We incorporate existing geospatial data sets depicting forest type and biomass, as well as annual fire and insect events to estimated annual forest biomass mortality (Mg C/ha) at 1-km resolution. Across the region, annual biomass mortality from fires averaged 2.24 ± 2.90 Tg C/yr from 1984-1995 and 6.30 ± 5.75 Tg C/yr from 1996-2011, with mortality during extreme fire years (2002, 2006-2008, and 2012) reaching ~10 to 20 Tg C/yr. Annual fire-induced mortality exhibited a positive trend over the record (slope=0.31 Tg C/yr, r²=0.24 , P<0.01) and correlated strongly with the growing-year climatic water deficit [CWD= sum(PPT-ET deficit); r² = 0.48, P < 0.05]. Annual biomass mortality from insects averaged 13.54 ± 9.92 Tg C/yr from 1996-2011 and reached ~20 to 30 Tg C/yr between 2007 and 2010. There was a steep positive trend in insect-induced mortality over the record (slope=0.96 Tg C/yr , r²=0.65, P<0.01). Cumulative biomass mortality from insects was highest in Colorado (19%), Montana (17%) and Washington (17%), whereas impacts from fire were highest in California (27%), Idaho (17%) and Oregon (15%). These disturbances had pronounced impacts on forested landscapes across much of the region during recent decades, with implications for carbon storage, wildlife habitat, forest resources, and water quality. Mitigating and adapting to ongoing climatic change necessitates improved understanding of current and potential future drought impacts on the magnitude and extent of forest disturbance in the western United States.

Presentation: 2015_Poster_Berner_185_283.pdf (3122k)

Presentation Type:  Poster

Session:  General Contributions   (Tue 4:35 PM)

Associated Project(s): 

• Related Activity: Related Activity or Previously Funded CC&E Activity not listed ...details

Poster Location ID: 185