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Effects of Enhanced Ultraviolet-B (UV-B) Radiation on Poplar Phytochemistry and HerbivoryEPA Grant Number: U915572
Title: Effects of Enhanced Ultraviolet-B (UV-B) Radiation on Poplar Phytochemistry and Herbivory
Investigators: Warren, Jeffrey M.
Institution: Washington State University
EPA Project Officer: Broadway, Virginia
Project Period: July 1, 1999 through July 1, 2002
Project Amount: $102,000
RFA: STAR Graduate Fellowships (1999) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objectives of this research project are to: (1) investigate the direct effects that ultraviolet-B (UV-B) radiation has on the biochemical properties of several forest tree species; and (2) correlate those changes with alterations in herbivore growth rates and feeding preference. The study will quantify the growth rate, biomass partitioning, photosynthesis, and foliar chemistry of Populus tricocarpa (black cottonwood) grown under 0X, 1X, and 2X ambient UV-B radiation (greenhouse and field trials). In addition, herbivory characteristics of UV-B irradiated P. tricocarpa foliage by Chrysomela scripta (cottonwood leaf beetle) will be examined. A related study will analyze the specific flavonoids in P. tricocarpa, Quercus robur, Pinus ponderosa, and Pseudotsuga menziesii foliage field-grown under 1X and 2X ambient modulated UV-B radiation exposure for quantity and composition.
P. ponderosa, Q. rubra, P. menziesii, and P. tricocarpa will be field grown under ambient and elevated UV-B radiation. Light racks consisting of UV-B 313 bulbs (Q-Panel Co., OH) connected to a computerized, modulated system will supply the supplemental UV-B radiation. This system adjusts individual UV-lamps based on continuous measurements of ambient UV-B radiation using a UV biometer (Solar Light Co., PA). A spectroradiometer (Optronics Laboratories, FL) and M.M. Caldwell's 1971 weighing function will be used to estimate values of biologically effective UV-B radiation and to adjust system output to maintain a 1X or 2X ambient BE UV-B treatment. The cottonwood leaf beetle will be used as an indicator of UV-B radiation induced changes in P. tricocarpa (90 reps). These organisms will be applied to the experiment in two ways: (1) in a choice-type or preference test, where the third (final) instar must choose on which tissue to feed (active involvement); or (2) larval growth rates, where the first instar is placed on various tissue types and its progress is monitored (passive involvement). Trees will be grown under the modulated system as well as indoors, with sample leaves selected by leaf plastochron index for the study: LPI 3 (very immature, preferred) and LPI 5 (less preferred). Leaf biochemical analysis (N, S, C:N, chlorophylls, flavonoids, photosynthesis, tannins, UV-B absorbing compounds) will be conducted. Mass regressions will be used to determine relative larval growth rate per unit leaf area. Larval and prepupal weight and development time will be used to quantify success on specific tissue.
The effects on flavonoids (which mitigate UV-B damage) is expected to be species and age specific. In addition, herbivory of black cottonwood by a leaf beetle is expected to be influenced by UV-B radiation induced shifts in carbon partitioning to various biochemical groups. This research project may provide important data regarding insects or pathogens feeding on foliage of woody species exposed to higher levels of UV-B radiation, using methods that focus on tree species important in terrestrial ecosystems.