Summary
This methodological study examined how isotope fractionation during soil N₂O reduction biases source partitioning estimates based on site preference values. Using 431 measurements from six soil incubations analysed by isotope ratio mass spectrometry, the authors demonstrate that closed-system models significantly overestimate the N₂O reduction effect on SP values, especially at high reduction rates. A dynamic apparent NIE function accounting for variable soil micropore reduction rates provides more reliable source partitioning estimates.
UK applicability
The corrected methodology for N₂O source attribution is directly applicable to UK soil monitoring and denitrification studies, particularly in temperate arable and grassland systems where N₂O emissions represent a key climate impact. The findings support more accurate greenhouse gas accounting from UK agricultural soils.
Key measures
N₂O site preference (SP) values (‰); N₂ and N₂O concentrations; net isotope effects (NIE); source contribution estimates (% from nitrification/fungal denitrification)
Outcomes reported
The study quantified how isotope fractionation during N₂O reduction affects site preference (SP) values and source partitioning estimates in soil. Three modelling approaches were compared to correct for net isotope effects and determine contributions from nitrification versus denitrification sources.
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