This proposal requests funds to purchase a Europa Scientific automated 15N/13C analysis system and associated peripheral equipment. The automated mass spectrometer system will be a self-supported, multiple user facility. Currently, we have identified projects in oceanography, soil science, botany, entomology, and forest science that will benefit directly from the purchase of this analytical system. This instrumentation will allow us to conduct 15N and 13C tracer experiments in terrestrial and aquatic ecosystems. The proposed research that would utilize the 15N/13C system includes the following studies: (1) N mineralization-immobilization and microbial biomass dynamics in soils and ocean waters; (2) transport of N compounds between plants through mycorrhizal hyphal connections; (3) associative N -fixation; (4) symbiotic N -fixation in legume- Rhizobium and actinorhizal-Frankia systems; and N uptake by phytoplankton and bacteria in marine ecosystems.
