Forest management treatments, tree resistance, and bark beetle resource utilization in ponderosa pine forests of northern Arizona

We show experimentally that forest restoration treatments that used thinning to reduce ponderosa pine density near Flagstaff, Arizona decreased the percentage of trees with successful bark beetle attacks induced by beetle community response to a Dendroctonus brevicomis pheromone. Underlying mechanisms for the beneficial effect of restoration treatments on tree resistance to bark beetles included stimulation of resin defenses. Resin flow after phloem wounding was greater in full and partial restoration treatments than the control in the first and second year after treatment. Five bark beetle species, Ips pini, D. brevicomis, D. valens, D. adjunctus, and D. frontalis, colonized and produced brood in the trees. There was a negative correlation between resin volume and number of brood that emerged from the bole. Niche breadth of the bark beetle species over bole positions was widest for I. pini and narrowest for D. brevicomis.