Landscape Scale Variation in Nitrous Oxide Flux Along a Typical Northeastern US Topographic Gradient in the Early Summer

Most previous studies investigating controls on nitrous oxide (N₂O) emissions have relied on plot-scale experiments and focused on relative homogeneous biotic and abiotic factors such as soil, vegetation, and moisture. We studied soil N₂O flux at 11 chamber sites along a 620 m topographic gradient in upstate New York, USA, aiming at identifying patterns of N₂O flux and correlating them to hydrological factors and soil substrate properties along the gradient. The topographic gradient is a complex slope with an overall gradient of 8%, covering plant communities of pasture, forest, alfalfa field, and riparian area from the top to the bottom. Mean fluxes of N₂O measured from late March to May ranged from 4.45 to 343 μg N m^?2 h^?1, and these fluxes were not significantly different among chamber sites located in different communities. With the descending of the slope, N₂O fluxes increased with the increase of soil water content, except for the riparian site. Statistically, N₂O fluxes were not strongly correlated with soil temperature, soil bulk density, and water filled pore space (p?>?0.05). Instead, strong correlations (p?2O fluxes and soil C and N content including NO ₃ ^? , NH ₄ ⁺ , total organic carbon, and C/N ratio. Multiple linear regression analyses including both soil physical and substrate properties highlighted the significance of soil NO ₃ ^? content and C/N ratio in regulating N₂O fluxes along the gradient.