iii DEDICATION

gratitude and love. iv ACKNOWLEDGEMENTS I would like to express my sincere gratitude to the many people who supported and helped me through the years. First and foremost I thank my advisor, Dr. John Qu, for his guidance, support and endless patience. He has always given me the freedom to explore my research ideas, and provided thorough instructions and insightful advice. My great thanks go to Dr. Yongqiang Liu for his instructions and help in my research and publications. He supported me as a committee member and SRS representative for USDA projects SRS-06-CA-11330136-051 and SRS-07-CA-11330136-167, which supported the research presented in this dissertation. I extend thanks and appreciation to Dr. Xianjun Hao for his instruction, insightful suggestions and discussions that I will forever value. I have been greatly impressed by his wide knowledge and dedication to science, which has always encouraged me. He reviewed and revised every proposal, project report and manuscript I submitted. Special thanks go to my committee members Dr. George Taylor and Dr. Ruixin Yang. Dr. Taylor provided instruction on my dissertation, revised my first peer-reviewed paper published early in this research, and gave wonderful advice on delivering scientific presentations. Dr. Ruixin Yang instructed me in many of the techniques applied in this research and helped revise this dissertation. Warm thanks go to all the group members in the EastFIRE Lab: Swarvan