Ayres Grants

The spatial patterning of population fluctuations is a fundamental emergent property of biological populations. In general, spatiotemporal patterns of abundance can be driven by dispersal, climate, and/or community interactions. Many animal populations, including most notable pest species, display population fluctuations that are synchronized over hundreds of kilometers, well beyond that expected by dispersal. This proposal aims to develop and test general process-based models of how climate and landscape patterns of host availability influence the spatiotemporal dynamics of an episodically abundant primary consumer, the southern pine beetle (Dendoctonus frontalis). Dendroctonus bark beetles, including D. frontalis, are the dominant source of biotic disturbance in coniferous forests of North America. They have recently killed trees over millions of hectares worth billions of dollars, with broad consequences for forest structure and function. Dendroctonus was prominent in arguments for the Healthy Forests Restoration Act of 2003. On a subcontinental scale, some regions experience more beetle damage than others, and some forests (ca. 500 km2) experience less damage than nearby forests even with similarly high abundance of dispersing beetles. Research will use physiological experiments, climatic analyses, studies of landscape composition and pattern in National Forests, field sampling, and spatially extensive historical data from beetle monitoring programs to test theoretical models regarding the role of climatic variation and the spatial structure of host plants (pines) in structuring subcontintal episodes of bark beetle outbreaks and collapses.

Intellectual merit. The work will add to our understanding of spatial synchrony in population dynamics, which is a fundamental but poorly understood property of populations. Research will contribute to the synthesis of physiological and population ecology, and aid in assessing the ecological consequences of climatic trends. Results will provide a unique test of the opposing hypotheses that (1) climatic warming will favor northern insect populations more than it disfavors southern populations vs. (2) the benefits of climate warming for northern populations will about balance the costs for southern populations Research will also develop and test demographically explicit models that predict effects of spatial patterns in host plants on the spatiotemporal dynamics of consumers. This would be the first study of how forest structure influences susceptibility to bark beetles across the extent of the southern pine forest biome.

Broader impacts. This research will contribute to general understanding of how climate and landscape structure influence plant pestilence. Specifically, it will improve short-term predictions of bark beetle pestilence, permitting detection and suppression efforts to be focused on the forests and regions that are at greatest risk. Results will further contribute to forest management by clarifying how alternative landscape configurations of host trees influence the long term risks of pestilence, and identifying regions where long term risks may be increasing or decreasing. Results might suggest nearly cost-free ways in which managed forest landscapes could be adjusted such that they sustain less pestilence while providing comparable ecosystem services. Studies will have particular value to the management of southeastern forests, especially the many National Forests, but may also contribute to stewardship of the other major coniferous forests of North America, all of which are impacted by bark beetles. Activities will contribute to the training of young scientists and strengthen connections between academic ecology and mission-based research at the U.S. Forest Service.