Soil N intensity as a measure to estimate annual N$_{2}$O and NO fluxes from natural and managed ecosystems

As natural and managed terrestrial ecosystems are major sources of the potent greenhouse gas nitrous oxide (N$_{2}$O) and of the atmospheric pollutant nitric oxide (NO), predicting the source strengths of these ecosystems is central to understanding and sustainably managing the N-oxides fluxes. Here we reviewed 82 high temporal resolution datasets on N$_{2}$O and 57 on NO fluxes collected from multi-site and multi-year field measurements, including grasslands, forests, and agricultural crops, to assess whether soil N intensity, that is, the time-weighted sum of soil NH$_{4}$$^{+}$ and/or NO$_{3}$$^{-}$ concentrations, can be used to estimate annual N-oxides emissions. We show that soil N intensity alone can accurately predict annual N$_{2}$O and NO emissions, and that the N$_{2}$O emission strength is exponentially related to the soil inorganic N load. Thus, measuring soil inorganic N loads should improve current estimates of N-oxide emissions from global terrestrial ecosystems, and open possibilities for monitoring N$_{2}$O mitigation efforts.