Landscape and Seasonal Patterns of Nitrous Oxide Emissions in a Semiarid Region

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Abstract
As a prerequisite for quantification of annual N2O emissions at a regional scale, this study was conducted to determine the landscape‐scale patterns and seasonal fluctuations of N2O emission and to demonstrate the linking relationships between large‐scale controllers and proximal factors of N2O emission. An area of the Black soil zone of central Saskatchewan, Canada, was stratified into three main textural areas: clay loam, fine sandy loam, and sandy. Within each textural area, representative sites were selected based on land use: unfertilized and fertilized cropland, fallow, pasture, and forest sites. A consistent landscape‐scale pattern of N2O emission was observed; footslope positions had higher N2O fluxes than shoulder positions. The role of topography is attributed to its strong influence on the hydrologic and pedologic processes in the landscape, which, in turn, regulate the soil factors controlling N2O emission at the microscale level. The seasonal fluctuation of N2O emission was influenced by precipitation. Pulses of activity were observed during summer, after rainfall events following N fertilizer application, and during spring thaw. At the regional scale, the sandy area had lower N2O emissions than the fine‐textured areas. The general order of N2O evolved among the land uses was forest < pasture < fallow ≈ unfertilized < fertilized cropland. Our results showed the importance of developing spatially based, predictive relationships between N2O emission and its controlling factors. Linking these relationships with large‐scale integrative variables, such as soil texture and land use, provides a means for extrapolating N2O fluxes from landscape to regional scale.

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