Ponderosa Pine Mortality and Bark Beetle-Host Dynamics Following Prescribed and Wildland Fires in the Northern Rocky Mountains, USA

Ponderosa pine delayed mortality, and bark beetle attacks and emergence were monitored on 459 trees for 3 years following one prescribed fire in Idaho and one wildland fire in Montana. Resin flow volume (ml) was measured on 145 fire-injured ponderosa pine 2 and 3 years post-fire. Logistic regression was used to construct two predictive ponderosa pine mortality models, and two predictive bark beetle-attack models. Post-fire delayed tree mortality was greater with the presence of primary bark beetles independent of diameter at breast height (DBH) (cm), and was greater in smaller diameter trees most likely due to direct effects of fire-caused injuries; mortality was lower in trees with less percent bud kill (PBK). The frequency of bark beetle attack was greater in trees with less percent bud kill and greater bole char height proportion (CHIP). Attack frequency was also greater on trees with higher percent bud kill and greater diameter at breast height. Classification tables for all predictive models were presented for application in post-fire management development. Multivariate ANOVA analyses were used to describe the effects of morphological and fire-injury variables on ponderosa pine resin production, and bark beetle attack preference and emergence. Resin production (ml) was significantly greater on burned than unburned trees. Resin flow increased significantly between June and July 1 year following fire and from June to August 2 years following fire. Resin flow was lower on the north bole aspect than the south and west aspects of unburned trees. Resin flow of burned trees significantly increased through the summer and was greatest in trees with high pre-fire live crown length (m) (LCL). Resin flow of unburned trees differed significantly by year, month, bole aspect, and live crown length. Resin increased by month and live crown length, decreased from 2005 to 2006, and was less on the northern bole aspect than all other aspects. Bark beetles preferred to attack fire-injured trees, especially within bole-scorched areas. No significant differences in bark beetle emergence were found between fire-injured and non fire-injured trees. On burned sites, beetle emergence was greatest from larger diameter trees with less severe fire injury. Western pine beetle (Dendroctonus brevicomis LeConte) had the greatest emergence from fire-injured ponderosa pine, and Ips pini (Say) had significantly greater emergence from non fire-injured ponderosa pine