Summary
This methodological study assessed how isotope fractionation during soil denitrification biases N₂O site preference values used for source partitioning. By analysing 431 measurements from six soil incubation studies and applying three different net isotope effect correction models (closed-system, open-system, and dynamic apparent NIE), the authors demonstrated that closed-system models significantly overestimate the N₂O reduction effect, particularly at high reduction rates. The dynamic apparent NIE function, which accounts for variable reduction rates in soil micropores, provides the most robust correction approach and substantially alters inferred source contributions.
UK applicability
These findings are applicable to UK soil research and denitrification studies, as the methodological corrections proposed improve the accuracy of N₂O source attribution in terrestrial ecosystems. The work supports better quantification of greenhouse gas emissions from UK agricultural and natural soils, informing climate mitigation policy and monitoring.
Key measures
N₂O site preference (SP) values (n=431); N₂ and N₂O concentrations; net isotope effects (NIE) during N₂O reduction; source contribution of N₂O from nitrification/fungal denitrification (%)
Outcomes reported
The study quantified the impact of isotope fractionation during N₂O reduction on site preference (SP) values and compared three different modelling approaches to correct for this bias in N₂O source partitioning. Recalculated SP₀ values and source contributions from nitrification/fungal denitrification differed significantly depending on the correction model applied.
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