Catfaces on Lodgepole Pine--Fire Scars or Strip Kills by the Mountain Pine Beetle?

Abstract

Abstract Basal scars on lodgepole pine, Pinus contorta, are common in central Oregon forests. Although foresters have generally called them fire scars, many result from old strip-attacks by the mountain pine beetle, Dendroctonus ponderosae--attacks that kill only one side of the stem. Strip-kill scars are usually wide at the bottom and narrow at the top, less than 4 m long, and on the north and east sides of the stem. Dating the scars showed that central Oregon suffered a beetle outbreak between 1920 and 1925 and another between 1900 and 1905. Observations of ring widths in stem sections show that a current outbreak and the previous one started when stand growth was very slow. The mountain pine beetle is apparently an important thinning agent that relieves competition in overstocked stands.