Soil gaseous nitrogen losses: Development and applications of nitrogen isotope approaches in China

Abstract

Soil gaseous nitrogen (N) losses, including nitric oxide (NO), nitrous oxide (N₂O) and dinitrogen (N₂), constitute an important component of ecosystem N budgets and strongly influence climate change. However, precisely distinguishing their highly complex production pathways remains a major challenge. Stable N isotope techniques, including ¹⁵N tracing and natural-abundance isotopocule approaches, provide critical tools for disentangling these pathways. Over the past two decades, Chinese researchers have developed and refined four major isotope-based source-partitioning methods, mainly including the three-pool source partitioning approach based on paired ¹⁵N labeling of NH₄⁺, NO₃⁻, and organic N, the combined ¹⁵N paired-labeling and isotope-pairing technique, the ¹⁵NO₃⁻ labeling and pairing approach coupled with nitrification inhibitors, and the N₂O isotopocule site preference (SP) approach. These approaches have been applied in forests and croplands, improving understanding of the relative contributions of denitrification, nitrification, heterotrophic nitrification, codenitrification, and anammox to gaseous N production. This review summarizes the principles, designs, strengths, limitations, and applications of these four N isotope approaches in Chinese ecosystems, highlighting contributions of Chinese researchers to methodological innovation and in situ applications, and providing a China-based perspective for global studies of soil gaseous N losses and methodological support for N cycle model optimization and mitigation strategies.

Graphical abstract

Keywords

nitrous oxide (N2O) / 15N tracing / isotope pairing technique / site preference (SP) / stable nitrogen isotopes

Highlight

	● Four representative nitrogen isotope approaches for soil gaseous N losses are systematically reviewed.
	● Chinese studies have advanced source partitioning of soil NO, N2O, and N2 production pathways.
	● Isotope approaches have improved quantification of denitrification, nitrification, heterotrophic nitrification, anammox, and codenitrification.
	● Future progress depends on in situ applications, low-disturbance labeling strategies, and better integration of methods, instruments, and models.

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