Abstract:
Prescribed burning is increasingly being used as a management tool to
reduce potential fuels on the forest floor and promote stand vigor through
removal of dense, crowded vegetation. Because fire affects both the
standing vegetation and the amount of downed wood in the ecosystem, it is
imperative to examine how organisms dwelling in woody debris are
responding to this alteration of habitat.
Woody debris chewing arthropods are important to nutrient cycling and
decomposition and serve as an important food source for wildlife. This study
focuses on two families of wood-boring beetles, (Coleoptera: Buprestidae
and Cerambycidae), which utilize woody debris for food and habitat. Most
species of buprestids and cerambycids do not attack live, vigorous trees but
are usually associated with stressed, fire-killed or recently downed trees.
Two studies were conducted examining the response of wood-boring
beetles to prescribed burning. First, an experimental study monitored the
response of wood-boring beetles (both adults and larvae) to various levels of
burn severity on logs placed in a designated prescribed understory burn site.
However, treatments were not applied evenly or as intended. Several logs
designated to be burned were not burned at all. Logs which did burn were
only slightly charred, with no bark consumption. Adult beetles flying to the
logs were monitored using flight intercept traps. Bark samples were taken to
determine percent utilization by beetle larvae. Results were compared
across percent of charring. No relationships between attraction or uti'ization
and percent char could be detected. The burned and unburned logs were
equally attractive to wood-boring beetles.
Second, a retrospective study was conducted, surveying adult woodboring
beetle populations in several prescribed burn sites, I to 15 years after
burning. Overall abundance, abundance of individual species, richness and
diversity were compared to adjacent control plots. While no significant
relationships existed between time since burn and abundance, numbers of
adult wood-boring beetles peaked in the first year after burning and remained
significantly higher on previously burned sites when compared to unburned,
control plots.
The goal of these two studies was to determine the effect of prescribed
burning on the habitat of wood-boring beetles and to aid in the development
of woody debris and fire management programs. While no causal inferences
could be made, wood-boring beetle populations appear to be responding
positively to prescribed burning in southwestern Oregon.
