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Western spruce budworm defoliation effects on forest structure and potential fire behavior.Author(s): S. Hummel; J.K. Agee
Source: Northwest Science. 77(2): 159-169
Publication Series: Scientific Journal (JRNL)
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DescriptionForest composition and structure on the eastern slope of the Cascade Mountains have been inﬂuenced by decades of ﬁre exclusion. Multilayered canopies and high numbers of shade-tolerant true ﬁr trees interact with western spruce budworm to alter forest structure and to affect potential ﬁre behavior and effects. We compared measurements taken in 1992 (early budworm outbreak) and 2000 (late budworm outbreak) from 21 permanent plots located in a late successional reserve south of Mt. Adams in Washington. Canopy closure decreased significantly, from a mean of 78% in 1992 to 43% in 2000, but the coarse woody debris load increased significantly during the same period, from about 40 Mg ha-1 to 80 Mg ha-1. Tree mortality was mostly in the smaller (<20 cm) diameter classes. Potential surface ﬁre ﬂame lengths increased significantly from 1.4 m in 1992 to 1.9 m in 2000, but changes in torching potential and independent crown ﬁre behavior were not significant. Projections using the First Order Fire Effects Model indicate that a wildﬁre in conditions similar to those in 2000 would not be of stand replacement severity and would leave 148 trees ha-1 and more than 34 m2 ha-1 of basal area.
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CitationHummel, S.; Agee, J.K. 2003. Western spruce budworm defoliation effects on forest structure and potential fire behavior. Northwest Science. 77(2): 159-169
KeywordsWestern spruce, budworm
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