Neglecting diurnal variations leads to uncertainties in terrestrial nitrous oxide emissions.

Narasinha J Shurpali,Pertti J Martikainen,Sami Haapanala,Olli Peltola,Mark Zahniser,Niina Hyvönen,Christina Biasi,Mari Pihlatie,Üllar Rannik,Timo Vesala,Perttu Virkajärvi,Simo Jokinen,Mari Räty,Ivan Mammarella,Saara Lind

doi:10.1038/srep25739

Abstract

Nitrous oxide (N2O) is an important greenhouse gas produced in soil and aquatic ecosystems. Its warming potential is 296 times higher than that of CO2. Most N2O emission measurements made so far are limited in temporal and spatial resolution causing uncertainties in the global N2O budget. Recent advances in laser spectroscopic techniques provide an excellent tool for area-integrated, direct and continuous field measurements of N2O fluxes using the eddy covariance method. By employing this technique on an agricultural site with four laser-based analysers, we show here that N2O exchange exhibits contrasting diurnal behaviour depending upon soil nitrogen availability. When soil N was high due to fertilizer application, N2O emissions were higher during daytime than during the night. However, when soil N became limited, emissions were higher during the night than during the day. These reverse diurnal patterns supported by isotopic analyses may indicate a dominant role of plants on microbial processes associated with N2O exchange. This study highlights the potential of new technologies in improving estimates of global N2O sources.

Highlights

Nitrous oxide (N2O) is an important greenhouse gas produced in soil and aquatic ecosystems
Despite the recent progress in quantifying the diverse N2O sources, the range of the global estimate is still large varying from 8.1–30.7 Tg N (N2O) a−1 owing primarily to the staggering spatiotemporal variation in the fluxes[3]
Attempts have been made to present a comprehensive estimate of the global N2O emissions using observations, bottom-up and inversion models[4]

Summary

Methods

Grass field had been harvested two weeks earlier (on 22 June 2011) and a second fertilizer dose of 15N-enriched Ammonium Nitrate (15NH415NO3, 10 AT-% (atom percent abundance) in both N forms at a rate of 100 kg N ha−1) was applied a day prior to the chamber flux measurements. The objective of this field campaign was to estimate the fraction of N2O derived from the 15N-enriched N-fertilizer. Water and CO2 gas were removed from the sample gas by a chemical trap (containing NaOH for CO2 and Mg(ClO4)[2] for H2O)

Author Contributions

Findings

Additional Information