Use of the inverse abundance approach to identify the sources of NO and N2O release from Spanish forest soils under oxic and hypoxic conditions

► Sources of NO and N2O formation were determined by a 15N triplet tracer experiment. ► Norg was the dominant source for N2O production under oxic conditions. ► Depending on the soil Norg contributed between 48 and 76% to total soil N2O release. ► Contribution of different soil N pools to N gas formation was site-specific.