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Forest Entomology Forest Health Biological Indicators

 

Project 1: Plant-insect interactions


The interaction between plants and insects is one of the important research areas in plant ecology and evolutionary biology. Basically, we are interested in how insects utilize plants as food sources and habitate; how plants resist the damage by insects; how insects act as a disturbance factor that can influence the nutrient cycling and dynamics of ecosystem . Among them, the resistant ability of plants to the attack of insect herbivory has been intensively studied. However, due to the complex biotic (e.g. plant species, physiological development stage) and abiotic (e.g. light, temperature, moisture, and soil nutrients) conditions, the resistance mechanisms of plants vary greatly among different species and change over time and space. That is, no single factor can account for all these variations.
I am currently working with Dr. Tom Kolb (School of Forestry, Northern Arizona University) and Dr. Karen Clancy (Rocky Mountain Research Station, USDA Forest Service, Flagstaff, Arizona). Our research is focused on the genetic variation of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco in resistance to western spruce budworm (Choristoneura occidentalis Freeman ) (Tortricidae). Douglas-fir is one of the world’s most important and valuable timber trees and is a major component of the forests in western Northern America. While western spruce budworm is one of the main defoliators that is primarily associated with the variety of Douglas-fir in the interior Rocky Mountain areas. The damage caused by the western spruce budworm ranges from the destruction of a single tree to entire forest ecosystem. This damage can result in the loss of productivity and decrease the health of forest ecosystem . Therefore, understanding the interaction between Douglas-fir and western spruce budworm will be helpful to the sound management of that system.
We study the genetic variation of Douglas-fir and its resistance mechanisms to the western spruce budworm on three diferent scales: mature trees in the field (Arizona and Colorado site), clones and half-sib seedlings in the greenhouse. A pairs of putatively resistant and susceptible mature trees were identified by their relative amount of crown damage after several years of heavy defoliation by western spruce budworm in 1980s. The pair of trees are nearby (less than 30 m) within each site and has the similar micro-climate conditions. The clones are obtained by grafting the branches that were taken from the upper 1/3 crown of mature trees in the field to one-year old stocks of Douglas-fir seedings. We test the following hypotheses simutaneously: photosynthetic compensation, growth vigor, foliage nutrients, foliage terpenes, and bud burst phenological asynchrony under the greenhouse experimental conditions. That is, compared to the susceptible tree phenotypes, the resistant tree phenotypes will have difference in at least on of the above measurements. Additionally, we hypothesize that western spruce budworm feeding on resistant tree phenotypes will have a lower fecundity in terms of fresh pupal weight, number of eggmasses per female adult, and eggmass viability. This comprehensive study will provide an understanding of the resistance mechanisms of Douglas-fir to western spruce budworm herbivory.