Summary
This analytical study examined how isotope fractionation during denitrification-driven N2O reduction biases site preference-based source partitioning in soils. Using 431 N2O measurements from six soil incubation studies, the authors compared three mathematical correction approaches—closed-system, open-system, and dynamic apparent NIE models—finding that the choice of model substantially affects estimated N2O source contributions. The dynamic apparent NIE function, which accounts for variable reduction rates in soil micropores, is likely more accurate than fixed-effect closed-system models when N2O reduction rates are high.
UK applicability
The findings are methodologically relevant to UK soil science and denitrification research, particularly for improving accuracy of N2O source attribution in temperate agricultural and pasture soils. The correction methods would enhance UK-based studies using isotopic tracing to quantify N2O emissions from different soil processes.
Key measures
N2O site preference (SP) values (n=431), N2O and N2 gas concentrations, net isotope effects (NIE) during N2O reduction, source partitioning estimates using two end-member isotopic mass balance
Outcomes reported
The study quantified how isotope fractionation during N2O reduction affects site preference (SP) values used to partition N2O sources in soils, and compared three mathematical correction approaches. Results showed that model choice significantly influenced estimated contributions of nitrification/fungal denitrification to total soil N2O emissions, ranging from 18.7% to 31.0%.
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