LTREB: Interaction of Below- and Above- Ground Herbivory in Forest Gap Formation:Long-Term Analysis of Underlying Mechanisms and Spatio-temporal Patterns

The overall purpose of this research is to explore the effects of, and the interactions between, herbivory on stems and herbivory on roots of red pine trees. Interactions between below-ground and above-ground processes such as herbivory are widely recognized as important but are poorly understood components of terrestrial ecosystems. In red pine, the group of herbivores that feeds on stems includes bark beetles and other boring insects; a different group of organisms feeds on tree roots. Previous results suggest that root-colonizing beetles also bring fungi into a few trees in new stands. These organisms do not kill mature trees, but they interfere with transport of materials (water, nutrients, carbon) between stems and roots. This interference reduces trees' ability to resist infection by bark beetles. At the same time that bark beetle infestation is increasing, fungi spread through roots and contribute to tree mortality. As infected trees die, different types of plants colonize the resulting empty space, leading to major vegetational changes in the forest. The specific objectives of the current study are to 1) study the effects that herbivory on roots has on susceptibility to stem herbivores, 2) measure movements of root beetles, bark beetles and their predators among trees and among forests, and 3) conduct experiments to determine the relative importance of stem-colonizing organisms, root-colonizing organisms, and their predators in tree mortality and gap (open forest space) formation. Because bark and root insects cause significant losses in commercial and natural forests, results from this study will aid forest management and public land management. The study will provide a better understanding of the scale at which crop diversity can reduce losses. The research will also contribute to science training by emphasizing interdisciplinary education at the undergraduate, graduate and postgraduate levels.