N2O Is an Important Piece of the Puzzle, but Seeing the Whole Picture Strengthens Denitrification Research

Abstract

For decades, denitrification research has been limited by the challenge of measuring fluxes of N2 against a background of high atmospheric concentrations. The methods developed to overcome this challenge all have strengths and weaknesses. Weitzman et al. (2021, https://doi.org/10.1029/2020JG006234) demonstrate the potential of one technique, the Nitrogen-Free Air Recirculation Method, to measure denitrification end-products in relatively undisturbed soil cores. This work reinforces the importance of N2 as the primary end-product of denitrification, accounting for over 86% of measured fluxes in all cores sampled, and reveals unforeseen hotspots of denitrification at depth in soil. These findings are consistent with a similar effort to improve estimates of N2O: N2O + N2 yield at the field scale that predicts N2 fluxes two to three times higher than predicted using previous estimates. By providing a more complete picture of N2O and N2 production in terrestrial systems, these efforts can strengthen denitrification research and support essential refinement of ecosystem models. The identification of unforeseen denitrification hotspots highlights the continued surprises of soil nitrogen cycle and should inspire mechanistic research into the biophysical drivers and communities that mediate denitrification hotspots.