Work

Combining the 15 N Gas Flux Method and N 2 O Isotopocule Data for the Determination of Soil Microbial N 2 O Sources

Year: 2024

Type: article

Abstract: ABSTRACT Rationale The analysis of natural abundance isotopes in biogenic N 2 O molecules provides valuable insights into the nature of their precursors and their role in biogeochemical cycles. However, current methodologies (for example, the isotopocule map approach) face limitations, as they only enable the estimation of combined contributions from multiple processes at once rather than discriminating individual sources. This study aimed to overcome this challenge by developing a novel methodology for the partitioning of N 2 O sources in soil, combining natural abundance isotopes and the use of a 15 N tracer ( 15 N Gas Flux method) in parallel incubations. Methods Laboratory incubations of an agricultural soil were conducted to optimize denitrification conditions through increased moisture and nitrate amendments, using nitrate that was either 15 N‐labeled or unlabeled. A new linear system combined with Monte Carlo simulation was developed to determine N 2 O source contributions, and the subsequent results were compared with FRAME, a Bayesian statistical model for stable isotope analysis. Results Our new methodology identified bacterial denitrification as the dominant process (87.6%), followed by fungal denitrification (9.4%), nitrification (1.5%), and nitrifier denitrification (1.6%). Comparisons with FRAME showed good agreement, although FRAME estimated slightly lower bacterial denitrification (80%) and higher nitrifier‐denitrification (9%) contributions. Conclusions This approach provides an improved framework for accurately partitioning N 2 O sources, enhancing understanding of nitrogen cycling in agroecosystems, and supporting broader environmental applications.

Source: Rapid Communications in Mass Spectrometry

DOI: 10.1002/rcm.9971