Radial Growth Assessment of Western Spruce Budworm Infested Douglas-Fir Trees on the Carson National Forest, New Mexico

Abstract

Growth of western spruce budworm (WSBW) infested Douglas-fir (Pseudotsugae menziesii) forests on the Carson National Forest, New Mexico, was assessed through dendrochronological analysis of increment cores extracted at breast height. Comparisons of indexed and filtered host and non-host (ponderosa pine [Pinus ponderosa]), tree-ring chronologies revealed that host tree growth was reduced during past and present WSBW outbreaks. The non -host chronologies were used to remove the non-WSBW growth effects from the host chronologies, and the corrected host tree growth indices were then used to assess growth loss during known outbreak periods. Maximum growth loss during one year was generally greater than 50 percent. The average growth loss for five year periods during outbreaks was approximately 30 to 40 percent, and the maximum growth loss between two years during an outbreak was usually more than 50 percent.