delta-N15 as an integrator of the nitrogen cycle

Natural abundances of the rare stable isotope of nitrogen, N-15, are now being used widely in research on N cycling in organisms and ecosystems. N-15 natural abundances are used in fundamentally different ways from traditional N-15 tracers by integrating N cycle processes via hi isotope fractionations and the mixing of various N-containing pools. This approach of using N-15 natural abundances still requires certain technical and conceptual advances before it can be used routinely in ecological research. Here,the basis of the natural abundance N-15 approach and opportunities for applying It In ecology are reviewed, and recent progress towards overcoming some of the key technical problems and in revealing large-scale patterns in N cycle processes is discussed.