del 15N Values for Tanana River Floodplain Soils and Xylem Sap Samples

Because soil microoorganisms preferencially discriminate either for or against heavy nitrogen isotopes in organic compounds we can learn something about the route these compounds take through any given system by looking at the isotopic ratio of heavy to light nitrogen within a pool as compared to the ratio for the system as a whole. An enriched pool means that 15N has been discriminated for, while a depleted pool means 15N has been discriminated against. By determining the del 15N values for soil protein, amino acids, ammonium, the soil microbial population, and plant roots and xylem we can learn something about where plants are deriving there nitrogen nutrition.