Coupling Thinning with Fertilization to Increase Tree Vigor and Decrease the Probability of Mountain Pine Beetle Outbreaks
Bark beetles are the most serious insect pests of conifer forests. Most tree mortality attributable to bark beetles occurs during outbreak years. This proposal examines potential stand treatments aimed at enhancing tree vigor and thus resistance to bark beetle attack and operational issues related to implementing those treatments. Although host resistance has received considerable research attention, few studies have examined the role of combined silvicultural strategies to enhance tree vigor prior to the initiation of an outbreak. The hypothesis we propose to test is that tree vigor can be improved by thinning of stands and the judicious application of fertilizer. The hypothesis will be tested by applying the treatments in the field, but examining the beetle population parameters in the laboratory so as to decrease the possibility of creating a
bark beetle infestation. The second hypothesis to be tested is that the treatments will have less impact on the on-site insect community structure than does an outbreak of mountain pine beetle. Insect community parameters will be measured and compared among treatments and within naturally-occurring mountain pine beetle outbreaks. The third hypothesis to be tested is that the cost of thinning and the amount of damage to the remaining trees will decrease with increasing thinning intensity. The cost of a thinning operation and the damage to the residual stand need to be minimized in order to make the proposed treatments economically feasible and practical.