Thursday, 20 November 2003: 9:00 AM
Douglas-fir beetle attack and tree mortality following wildfirePoster PDF (242.2 kB)
A major concern after wildfires is the buildup of bark beetle populations in fire injured trees, and subsequent attack and population buildup in adjacent unburned areas. To examine this concern, we documented fire injury and insect attacks in Douglas-fir (Pseudotsuga menziesii) on the 2001 Green Knoll Fire, Wyoming to determine attack preferences, brood production, and emergence densities in different levels of fire-injured trees. Tree injuries of crown scorch, ground char, bole char, and basal girdling were recorded in mixed-severity burn areas. Douglas fir beetle (Dendroctonus pseudotsugae) attack densities and brood production were sampled on two sides of infested trees in the fall of 2002. Sampled trees were organized into different combinations of crown scorch and basal girdling. Cages (1x2 ft) were installed on a subsample of trees in each category in spring of 2003 to sample beetle emergence densities. Crown scorch, pre-fire vigor, dbh, and the interaction of crown scorch and basal girdling were significant variables in explaining whether a tree was attacked by Douglas fir beetle. The number of brood sampled in fall was significantly affected by the percent crown scorch but not the percent basal girdling; however, the emergence the following spring was not significantly correlated with either crown scorch or basal girdling. Further analyses of attack and tree injury correlations are planned.