Proposal summary
| The effect of host species and infestation
size on populations of Dendroctonus frontalis USDA Competitive Grant: 2004-2007. |
| Understanding the causes of outbreak dynamics is fundamental to basic ecology and pest management. Outbreak dynamics of Dendroctonus frontalis probably involve complex endogenous dynamics and recent amelioration of environmental constraints. Evidence indicates that D. frontalis populations (1) display positive density-dependence (allee effect), which is intrinsically destabilizing to population dynamics, and (2) have been permitted to attain larger and more frequent outbreaks by the increased prevalence in contemporary forests of loblolly pine, because this species is less resistant to D. frontalis than longleaf pine. These empirical patterns appear to be robust and consequential. In fact, they are among the most widely accepted generalizations about biotic disturbance in southern pine forests. However, recent data have cast doubt on the prevailing explanations for these patterns, and led to plausible alternative hypotheses. We will evaluate two sets of multiple working hypotheses to explain why (1) infestations that begin large tend to grow at higher relative rates than those that being small, and (2) why longleaf stands are more resistant to D. frontalis than loblolly stands. Results will lead to improved understanding of population dynamics in D. frontalis, and could aid in developing general approaches for understanding (1) allee effects in pest populations, and (2) how demographic processes that operate at different scales can produce spatially complex patterns in population dynamics and biotic disturbance. Results may contribute to forest management by providing information that aids in (1) prioritizing control efforts, and (2) considering the potential effects on bark beetle disturbance from silivicultural decisions regarding site selection for different native pine species, stocking densities, and thinning practices. Finally, the research will formalize linkages between pest monitoring programs and abundance patterns, which could improve predictions of short-term abundance and long term outbreak probabilities. Overall, this research will contribute to agricultural issue #6 in the RFA, “Natural resources and environmental quality”. |
| Investigators: Matthew P. Ayres, Dan Slone, Sharon Martinson, Kier Klepzig |