Ostfeld, R. S. DEB-9615414 The PIs propose to test the importance of direct and indirect effects in oak forests of southeastern New York State. Episodic mast production by oak trees appears to cause transient increases in the density of rodent populations. Rodents, in turn, appear to regulate low-density gypsy moth populations and are the primary reservoirs of the tick that carries Lyme disease. The PIs will simulate mast production and measure the response in rodent population levels. The effect of changes in mouse population densities will be determined for survival of gypsy moth pupae and density of egg masses, and parasitization rates of larval ticks and nymphal tick abundance. The PIs will conduct rodent removal experiments to test the hypothesis that rodent population density regulates gypsy moth population dynamics only during the low phase of the moth cycle. Modeling of the interaction will determine the sensitivity of system behavior to variation in the functional response of rodent predation and acorn consumption and to variation in the rhythm of the masting cycle. In addition to contributing to a more complete understanding of the factors determining the structure and dynamics of ecological systems, the results of this study will be applicable to the management of deciduous forests and to two factors affecting quality of life in the northeast - gypsy moth defoliation and the rapid spread of Lyme disease.
