Abiotic dissolution and biological uptake of nitrous oxide in Mediterranean woodland and pasture soil

Soil is generally regarded as a net emitter of nitrous oxide (N2O). However, there are numerous field studies showing net uptake of N2O from soil in different ecosystems. Consumption of N2O may be abiotic (absorption by water; adsorption by soil matrix) and biotic (microbial reduction of N2O). This study is the first using undisturbed soil cores to determine the capacity of soil to consume N2O and discuss the fate of N2O. We exposed the base of undisturbed soil cores from Mediterranean pasture and woodland soil to elevated concentrations of N2O and sulphur hexafluoride (SF6; as tracer gas). Headspace concentrations of N2O and SF6 were determined over time and consumption rates of N2O were calculated ranging from 148.8 +/- 19.8 ng NN2O min(-1) g(-1) to 163.8 +/- 17.2 ng N2O min(-1) g(-1) in woodland soil and from 117.2 +/- 36.1 ng NN2O min(-1) g(-1) to 145.1 +/- 19.4 ng N2O min(-1) g(-1) in pasture soil. Absorption of N2O by soil water contributed 17-49% of the total N2O consumption. The remaining N2O consumed by the cores was due to adsorbtion by the soil matrix and/or reduction by microbes. Mediterranean soil from different ecosystems with different nitrogen (N) loads has a great potential to store and consume N2O, if exposed to an N2O elevated atmosphere. Crown Copyright (c) 2015 Published by Elsevier Ltd. All rights reserved.