Douglas-Fir Beetle Response to Artificial Creation of Down Wood in the Oregon Coast Range

Abstract

Douglas-fir beetle populations were monitored before and after thinning and felling of trees to create down wood in an 88-year-old Douglas-fir plantation in the Oregon Coast Range. Treatments included an unthinned control, thinning to a target of 75 trees/ha, and thinning to a target of 150 trees/ha. Actual mean tree densities on the plots after thinning were 406, 102, and 154, for the control, 75 trees/ha, and 150 trees/ha treatments, respectively. Fifty trees/ha were felled and left on all thinned plots to create down wood for ecological values. Catches in pheromone-baited traps indicated that the local beetle population increased for 1 year in response to felling and leaving large diameter trees in partial shade. Douglas-fir beetle entrance holes and brood were significantly more abundant on the sides of felled trees and wood borers were significantly more abundant on the upper surface suggesting that treatments that provide maximum exposure of felled trees will create the least favorable habitat for Douglas-fir beetles. However, there were no differences in Douglas-fir beetle entrance holes or brood densities in felled trees between the two thinning intensities. Douglas-fir beetle-caused tree mortality was significantly higher on thinned plots with residual felled trees compared with unthinned controls, although infestation levels were low on all plots (<2 trees/ha). The small increase in beetle-caused tree mortality associated with leaving felled trees would be unlikely to interfere with resource management objectives. These results are applicable to mature, managed forests west of the Cascades with relatively low Douglas-fir beetle populations. In different regions and stand types, or under different environmental conditions, beetle populations could increase to higher densities, remain at high densities longer, and cause higher levels of tree mortality. West. J. Appl. For. 21(3):117–122.

Do birds help trees grow? An experimental study of the effects of land‐use intensification on avian trophic cascades

“…Bark beetles can negatively impact tree growth and cause mortality directly or by acting as vectors for black stain root disease (Leptographium wageneri), a lethal fungal pathogen that appears to have increased in recent years in the Oregon Coast Range (Oregon 2017). Douglas-fire beetles can increase infestation rates when large amounts of downed wood are present (which was not the case for our study), such as from large-scale disturbance or thinning (Ross et al 2006). Therefore, in a scenario where changing environmental or management conditions could lead to an increase in the densities of these pests, the trophic effects of bird predation may become more valuable to crop-tree production.…”

The Interacting Influence of Fire and Tree Characteristics on Douglas-Fir Beetle Host-Tree Selection Five Years Post-Fire

“…Post-fire tree mortality is an important factor that land managers must consider when attempting to establish desired forest conditions [7,24,25], and the interactions between fire and tree-boring insects must be included in these considerations. Actions such as the deployment of anti-aggregation hormone packets or the targeted removal of high-risk trees may reduce the likelihood of epidemic outbreaks and preserve individual high economic or social value trees [26][27][28][29]. Using a machine learning methodology, we developed a recursive partitioning decision tree model that uses fire injury, tree, and stand characteristics as parameters.…”

The Western Bark Beetle Research Group: a unique collaboration with Forest Health Protection-proceedings of a symposium at the 2007 Society of American Foresters conference

“…Land managers have had high expectations for the development of pheromones and other behavioral chemicals for bark beetle control because of limitations encountered with other pest control methods. For example, it is widely accepted that maintenance of stand health and vigor through vegetation management is the most durable approach to "beetle-proofing" stands (Amman et al 1991;Amman and Logan 1998;Fettig et al 2006cFettig et al , 2007Whitehead and Russo 2005), but management objectives sometimes require maintenance of high basal area (Andrews et al 2005) and/or the creation of down woody material that increases stand susceptibility to bark beetle attack (Ross et al 2006). Treatments to reduce stand density are also time-consuming and can incur regulatory obstacles that may delay the implementation of treatments until stands have already been compromised by bark beetle attacks.…”