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Soil Temperature Dynamics Modulate N₂O Flux Response to Multiple Nitrogen Additions in an Alpine Steppe
JGRG Journal of Geophysical Research: Biogeosciences
Format: Journal Article
Publication Year: 2018
Pages: 3308 - 3319
Source ID: shanti-sources-106266
Abstract: Emissions of nitrous oxide (N₂O) contribute to global warming and stratospheric ozone depletion. Anthropogenic N₂O emissions predominately result from the addition of synthetic nitrogen (N) fertilizers to terrestrial ecosystems. Usually, an exponential increase in N₂O emissions occurs as N addition rates increase to exceed plant demands. However, most evidence to date is from temperate areas, with little information available for alpine ecosystems. Here we examined the changes in N₂O flux under eight N addition levels and the mechanisms regulating these changes in a Tibetan alpine steppe. Our results showed that N₂O emission rate increased linearly with increasing N additions. Even when soil N availability exceeded plant N uptake, no sharp N₂O emissions were observed. The likely explanation was that decreased soil temperature limited the growth of nitrification-related microorganisms, mainly ammonia-oxidizing archaea, which further attenuated the positive response of N₂O emissions to excess N supply. These findings suggest that the N-induced changes in soil temperature regulate the growth of nitrifying microorganisms and the subsequent N₂O fluxes in this alpine steppe, and the exponential N₂O emission-N rate relationship observed in warm regions may not be simply extrapolated to alpine ecosystems.
N₂O emission exhibited a linear, rather than an exponential, response to increasing N additionsN₂O flux was explained by the changes in AOA along this N addition gradientDecreased soil temperature limited the growth of AOA, weakening the positive response of N₂O flux to excess N supplies