Kenneth F. Raffa - US grants

Research programs of five principal investigators at the University of Wisconsin (Madison) focus on the secondary chemistry (allelochemicals) of plants. These programs involve studies of: 1. Effects of genetic factors and environmental stresses plant secondary chemistry. 2. Consequences of variation in plant chemistry for plant resistance to insect and mammalian herbivores. 3. Genetic engineering and in vitro production of unique organic compounds by plants. The requests HPTLC system is essential for expeditious progress in these research areas because it is the only analytical system capable of rapid chromatographic analysis of the large numbers of samples required. Moreover, it is ideally suited for analysis of labile compounds, which are central to the work of several of the research programs. Without the capabilities offered by HPTLC, progress in the respective research areas will be seriously impeded.//

9408264 Raffa We know very little about the extent to which pheromone chemistry of prey species has evolved in response to selection generated by predators that use pheromones to locate prey. The PI is studing the ecological implications of bark beetle-predator semiochemical interactions. He will test the hypotheses that 1) subtle shifts in pheromone chirality and secondary components may facilitate escape from predators, while retaining intraspecific functions, and 2) variation in bark beetle semiochemistry can affect reproductive success within colonized trees. This research will yield new insights into the ecological relationships between insect predators and their prey, and , in particular, how prey adapt to reduce attack by predators that home in on their chemical communication systems (pheromones). Because bark beetles are one of the major challenges to sustainable forestry, the results of this research will have important application to management of forests and bark-beetle outbreaks.

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.

Bark beetles are native insects that exert dramatic effects on forest ecosystems. These include contributions to basic ecosystem processes such as nutrient cycling and gap formation, impacts on biodiversity, and, at times, widespread mortality to millions of trees. The frequency and extent of intermittent bark beetle outbreaks appear to be influenced by several human impacts, including climate change, forest fragmentation, and various management policies. This research will use ground sampling, tree physiological and biochemical analyses, and satellite imagery to evaluate the effects of a major form of natural and human disturbance, fire, on susceptibility of lodgepole pine to the mountain pine beetle, and on mountain pine beetle reproduction. It also will test how fire injury affects reproduction by other, non tree-killing bark beetles that compete with mountain pine beetle.
This work will contribute to our basic understanding of how disturbance agents interact in conifer forests, and provide useful information for resource managers. It will contribute to science infrastructure through the training of undergraduate students, graduate students, and postdoctoral associates. This interdisciplinary study will be conducted in the Greater Yellowstone Ecosystem, where it will interface with other collaborators from various institutions.