Funding is requested for an isotope ratio mass spectrometer. The instrument will be used primarily to support research with 15N and 113C in the biological science area, with major users from the ecological, plant, natural resource, and soil sciences. IN the soil sicnece area, 15N will be used to study the effects of below ground N cycling processes on N availability to plants and, together with 13C, the dynamics of soil organic matter. Aquatic ecologists will use 15N to study N fixation in awuatic systems and 15N and 113C to investigate interations between aquatic community structure and nutrient cycling. Plant physiologists propose to use 13C for measurement of water use efficiency and root growth and respiration in trees subjected to environmental strees. Natural resource scientists propose to use 15N in a bioassay of the N nutrient status of trees, in studying the role of N allocation within plants on succession in northern hardwood forests, and to trace transport and transformation of added N in a forest ecosystem. Further, natural abundance 13C measurements will be used to determine the influence of terrestrial liming on lake alkalinity.
