This research proposal addresses the fundamental ecological cause of outbreaks of damaging forest insects in China and the United States. In this proposal experiments are outlined that will test the role of forest stand conditions (age, density, genotype) in predisposing pine forests to outbreak by an economically important group of forest defoliators - pine sawflies (Hymenoptera: Diprionidae). Despite extensive literature implicating stands conditions as a major factor in forest insect outbreaks little is known about the fundamental mechanisms responsible for this universal phenomenon. Nearly identical pine sawfly outbreak patterns occur in Pinus ponderosa forests of the western United States and Pinus yunnanenis forests of central China. Pine sawfly outbreaks are restricted to low density stands of a restricted age class. A strongly experimental approach is proposed to rigorously test the importance of stand conditions in predisposing trees to sawfly outbreaks in both China and the US. Stand manipulations will be conducted to experimentally create stand densities that replicate the densities of stands known to support pine sawfly outbreaks. The importance of two hypothesized mechanisms for the observed outbreak patterns will be tested. The basic experimental design is to conduct parallel studies in Sichuan Province, China and Arizona, USA. Specific research activities to be conducted include a 1 month visit by Dr. Wagner and 4-6 months of field research each year by a doctoral student and research technicians from Northern Arizona University. This research will assisted by a scientists and research staff of the Experiment Center of Sichuan Provincial Academy of Forestry Science. Similarly a scientist from the Sichuan Forestry Academy will conduct research in Arizona for 4-6 months each year for two years. Short term visits by Chinese scientists to research facilities and study areas in the US will also be supported. Dr. Wagner and Mr. Hend Xiao both have extensive previous experience working with pine sawflies on pine species. This project will improve our basic understanding of the causes of forest insect outbreaks, improve the training of US and Chinese scientists, and enhance scientific and cultural exchange between China and the United States.
