ATTACK OF BARK BEETLES ON FORESTS IS RECORDED IN THE ISOTOPIC COMPOSITION OF BOTH MODERN RESINS AND CRETACEOUS AMBER

δ ¹³C of plant tissues is known to reflect water stress. To date, most studies of trees have focused upon the variability observed in xylem, or partitioning between plant structures. Although these investigations provide insight into forest conditions at annual intervals, or at different positions within the canopy, they do not address short-term events. Bark burrowing beetles kill trees by girdling their trunks and introducing fungi which disrupt water supply to the canopy. Secondary metabolites, such as modern resin or ancient amber, may record the progression of insect infestations. Conifers maintain a store of constitutive resin within their resin ducts and produce voluminous defensive resin when stressed. Variability in the stable isotopic composition of these two resin types allow us to observe the onset of insect attack. Here we present preliminary results from an investigation into the effects of Dendroctonus ponderosae (mountain pine beetle) infestation in northern Alberta, Canada upon the carbon and hydrogen composition of Pinus contorta latifolia (lodgepole pine) resin. These data (δ¹³C of resin from infested trees ranging from -27.55‰ to -25.61‰, -26.80‰ mean; un-infested tress ranging from -29.54‰ to -27.43‰, -28.23‰ mean) show that there is discernible ¹³C enrichment in resins released during early stages of bark beetle infestation. Additionally, resin hydrogen composition provides an indicator of the local meteoric water values during resin production, and the approximate duration of exposure for individual resin samples. Distributional trends observed within the modern resin stable isotope values appear analogous to those observed within Turonian (Late Cretaceous) New Jersey amber (δ¹³C of barren amber with -22.41‰ mean, insect-bearing amber with -21.91‰ mean, and fire-related amber with -20.60‰ mean). Amber from this deposit is known to contain fossil bark beetles, and the bulk of the deposit is thought to have formed under similar infestation conditions. Such analogies offer insights into paleoforest conditions and the events surrounding amber production.