Fate of nitrogen inputs to terrestrial ecosystems: a meta-analysis of ecosystem scale 15N Tracer Studies

Nitrogen (N) is an essential nutrient for all living organisms and often limits net primary productivity in terrestrial ecosystems. However, human activity has led to the doubling of global N inputs to terrestrial ecosystems. This has prompted considerable interest among ecologists to understand controls over the fate of N inputs to ecosystems, and the relationship between N inputs and cycling of other elements, particularly carbon. Recent improvements in stable isotope methodology and automation of mass spectroscopy have enabled ecologists to apply stable isotopic tracers at large spatial scales. Using enriched 15N isotopes, we can now track a specific cohort of N inputs throughout an ecosystem and determine its fate. To date, there have been over 20 studies carried out in a diverse array of ecosystem types. We have compiled a meta-dataset of terrestrial ecosystem 15N tracer studies for comparison of the fate and redistribution of N across sites and ecosystem types.