Beyond red crowns: complex changes in surface and crown fuels and their interactions 32 years following mountain pine beetle epidemics in south-central Oregon, USA

TitleBeyond red crowns: complex changes in surface and crown fuels and their interactions 32 years following mountain pine beetle epidemics in south-central Oregon, USA
Publication TypeJournal Article
Year of Publication2019
AuthorsWoolley, T
Secondary AuthorsShaw, DC
Tertiary AuthorsHollingsworth, LT
Subsidiary AuthorsAgne, MC, Fitzgerald, S, Eglitis, A, Kurth, L
JournalFire Ecology
Keywordsbark beetles, Dendroctonus ponderosae, fuels, insects and fire, lodgepole pine, Pinus contorta var. murrayana, technical reports and journal articles


Mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB), a bark beetle native to western North America, has caused vast areas of tree mortality over the last several decades. The majority of this mortality has been in lodgepole pine (Pinus contorta Douglas ex Loudon) forests and has heightened concerns over the potential for extreme fire behavior across large landscapes. Although considerable research has emerged concerning influence of MPB on forest fuels, there has been little work in the climax lodgepole pine forests of south-central Oregon, USA. Specifically, we assessed changes in forest structure and crown and surface fuels across a chronosequence of time since mountain pine beetle (TSB) epidemics in south-central Oregon (1979 to 2008).


We classified four distinct periods in which significant changes occur in fuels: overstory mortality stage (2 to 4 years TSB), standing snag and snag fall stage (5 to 13 years TSB), regeneration stage (14 to 25 years TSB), and overstory recovery stage (26 to 32 years TSB). Multivariate analyses indicated changes in crown fuels and forest structure following MPB epidemics were driven primarily by basal area of live and standing dead trees, canopy bulk density, canopy base height, and canopy height. Substantial declines in canopy bulk density occurred early (2 to 5 yrs) following beetle activity and slowly recovered over time. The pattern of succession of surface fuels following a MPB epidemic was largely determined by changes over time in 10-h, 100-h, and 1000-h fuel loads, in addition to increasing fuel bed depth. The 100-h fuel load increased over the entire 30-year period, while 1000-h fuel load reached an asymptote 14 to 26 years following epidemic initiation. Live woody fuels increased through the initial overstory mortality stage and began to decrease during the overstory recovery stage.


Our key findings concerning changing fuels and forest structure following a MPB epidemic in south-central Oregon lodgepole pine forests include: 1-h fuels and litter changed little over time, surface fuel loads changed dramatically between the standing snag and the regeneration stages, lodgepole pine remained dominant, and canopy bulk density was low throughout the chronosequence. These factors point to the perpetuation of a lodgepole pine dominated system with a mixed-severity fire regime well into the future.