Two-year Bark and Ambrosia Beetle Diversity Study at the Talladega National Forest in the Southeastern United States

Abstract

Over two year period (March 2008 to February 2010), bark and ambrosia beetles were captured in three different trap types (intercept panel, flight intercept and pitfall) at the Talladega National Forest in Chilton, Bill and Perry Counties in Alabama. Of 85,876 total insects captured, 23,030 were Hylastes salebrosus Eichoff, 21,283 were Gnathotrichus materiarius and 8,004 were Ips grandicollis. The number of root dwelling insects captured emphasized their importance in the loblolly pine ecosystem. Several beetle species were more common at predicted loblolly pine decline plots compared to predicted non-decline plots, including several ambrosia beetle species. Elevated numbers of beetle species that feed on weakened trees indicated that loblolly pine decline may be occurring in the study plots. Trees in decline are less capable of resisting insect attacks. Previous thinning that occurred at 8 of the 24 study plots during the 1990s appeared to reduce the insect numbers in declining plots. Loblolly pine decline may be managed through careful thinning. Intercept panel traps captured many species associated with the mid-bole and higher of trees in addition to insect species associated with tree roots. Intercept panel traps captured the broadest representation of insects and appeared to be a useful trap to supplement pitfall traps in the capture of root-feeding bark beetles. Flight intercept traps captured many of the same species as intercept panel traps but captured fewer individuals of all species. iii Invasive non-native plants were detected at study plots during 5 surveys conducted in 2008 and 2009, but the non-native plants observed were generally common across the region. Most non-native plant observations occurred along roads and adjoining private property did not appear to facilitate invasion. Non-native plants were more common at plots that had been thinned during the 1990s than at plots that had not been thinned at all during the rotation, affirming previous studies that found non-native plants respond to disturbance. Biomass removal and conventional thinning was expected to take place at all the research plots predicted to have loblolly pine decline. Conventional precommercial thinning is expected to increase short-term bark and ambrosia beetle populations because of the release of attractant chemicals and increase of logging debris at the plots that would follow treatment. Insect populations following biomass removal plots would not be expected to increase to the same extent as in conventionally thinned plots because of the habitat removal and the subsequent release of remaining trees. Both biomass removal and conventional thinning treatments are expected to increase invasive plants because of the disturbances involved. Expected follow-up research will compare insect collections and non-native plant totals from before and after the treatments.