Summary
This methodological study demonstrates that using a closed-system model with fixed isotope effects significantly overestimates N2O reduction bias on site preference values, particularly under high reduction rates. By comparing three correction approaches (closed-system, open-system, and dynamic apparent NIE models) across 431 soil samples, the authors show that accounting for variable reduction rates in soil micropores via a dynamic apparent NIE function reduces estimated nitrification/fungal denitrification contributions from 18.7% to 28.3%, yielding more accurate N2O source partitioning.
UK applicability
The findings are applicable to UK soil research programmes seeking accurate N2O source attribution for understanding greenhouse gas emissions from UK agricultural and grassland soils. The dynamic NIE correction method may improve precision in future UK denitrification studies and support more reliable emission factor development for UK farming systems.
Key measures
N2O site preference (SP) values (‰); net isotope effects (NIE) during N2O reduction; N2O source contribution percentages from nitrification/fungal denitrification versus bacterial denitrification; N2O and N2 concentrations measured by gas chromatography and isotope ratio mass spectrometry (IRMS)
Outcomes reported
The study measured N2O site preference (SP) values from 431 soil samples across six incubation studies and quantified how different correction models for N2O reduction affect the partitioning of N2O sources between nitrification/fungal denitrification and bacterial denitrification.
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