Ecological Archives E094-227-A1
Brian J. Harvey, Daniel C. Donato, William H. Romme, Monica G. Turner. 2013. Influence of recent bark beetle outbreak on fire severity and postfire tree regeneration in montane Douglas-fir forests. Ecology 94:2475–2486. http://dx.doi.org/10.1890/13-0188.1
Appendix A. Study area and recent Douglas-fir beetle outbreak history.
Fig. A1. Map of the study area, plot locations, and regional context (inset). The Gunbarrel Fire burned on the Shoshone National Forest, Wyoming (USA) during summer 2008.
Recent Douglas-fir beetle outbreak history
Douglas-fir mortality from the Douglas-fir beetle was first recorded from USDA aerial detection surveys (ADS) in and around the study stands in 1995. By the year 2000, 27% of the eventual beetle-caused tree mortality had occurred and at the peak of the outbreak (trees infested in 2001 and mapped as dead in 2002), 71% of the eventual beetle-caused tree mortality had occurred. As the outbreak subsided by 2005, 95% of the cumulative mortality had occurred, meaning 95% of beetle-killed trees were actively infested in 2004 or earlier (Fig. A2). Trends were similar throughout the entire Gunbarrel Fire area. As trees killed by the Douglas-fir beetle can take up to one year for the canopy to change color (Belluschi and Johnson 1969), observed mortality (typically red-stage crowns visible from an aircraft) detected in ADS is likely from infestation the year before the mapping flight (Dodds et al. 2006, Meddens et al.2012). As the red stage typically lasts 2–3 years (Belluschi and Johnson 1969, Donato et al. 2013), only a very small percentage of trees (<< 5%; similar to background mortality levels in uninfested stands) would have been in the red stage at the time of the fire, and essentially all were in the gray stage. Pre-fire photos of the area within and surrounding the 2008 Gunbarrel Fire further illustrate the gray-stage condition of the forest prior to the fire (Figs. A3–A4).
Fig. A2. Cumulative yearly tree mortality attributed to the Douglas-fir beetle outbreak in the study stands, using USDA aerial detection survey data (http://www.fs.usda.gov) for each plot location. This illustrates that nearly all new mortality attributed to Douglas-fir beetle had ceased by 2005, three years prior to the Gunbarrel Fire. NOTE: Yearly cumulative mortality does not represent the percentage of all trees in a stand, but rather the cumulative percentage of the trees eventually killed by Douglas-fir beetles during the recent outbreak that were dead by a given year (i.e., 100% of the mortality caused by Douglas-fir beetle equated to a mean of 228 trees/ha, or 24% of all trees in study stands). Trends followed a similar temporal pattern for the entire Gunbarrel Fire area.
Fig. A3. View of the Libby Creek drainage (the western-most drainage burned in the Gunbarrel Fire and sampled in this study) in 2007, one year before the 2008 Gunbarrel Fire. Trees in foreground are beetle-killed Douglas-fir trees in the gray stage; no current outbreak or red-stage trees are visible. Photo credit: Linda McCoy, former owner of Crossed Sabres Ranch, Cody, Wyoming.
Fig. A4. General stand-level outbreak conditions nearby the study area in 2006 (two years before the fire). Photos were taken from study plots measured for Douglas-fir outbreak severity in 2006, located 670 m (a) and 700 m (b) south of the eventual fire perimeter (Simard et al. 2012). Dead trees are beetle-killed Douglas-fir trees in the gray stage; no current outbreak or red-stage trees are visible. Photo credits: Martin Simard.
Belluschi, P. G., and N. E. Johnson. 1969. Rate of crown fade of trees killed by Douglas-fir beetle in southwestern Oregon. Journal of Forestry 67:30–32.
Dodds, K. J., S. L. Garman, and D. W. Ross. 2006. Landscape analyses of Douglas-fir beetle populations in northern Idaho. Forest ecology and management 231:119–130.
Donato, D. C., B. J. Harvey, W. H. Romme, M. Simard, and M. G. Turner. 2013. Bark beetle effects on fuel profiles across a range of stand structures in Douglas-fir forests of Greater Yellowstone. Ecological Applications 23:3-20.
Meddens, A. J. H., J. A. Hicke, and C. A. Ferguson. 2012. Spatiotemporal patterns of observed bark beetle-caused tree mortality in British Columbia and the western United States. Ecological Applications 22:1876–1891.
Simard, M., E. N. Powell, K. F. Raffa, and M. G. Turner. 2012. What explains landscape patterns of tree mortality caused by bark beetle outbreaks in Greater Yellowstone? Global Ecology and Biogeography 21:556–567.
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