Vegetation composition modulates the interaction of climate warming and elevated nitrogen deposition on nitrous oxide flux in a boreal peatland

Northern peatlands with large organic nitrogen (N) storage have the potential to be N2O hotspots under climate warming, elevated N deposition, and vegetation composition change caused by climate change. However, the interactions of these three factors and the primary controls on N2O fluxes in peatlands are not well-known. Here, the three factors were manipulated in a boreal bog in western Newfoundland, Canada for 5 years. We found that warming mitigated the positive N effect on N2O fluxes in the mid-growing season under intact vegetation owing to the increase of available N uptake by vegetation and less N for N2O production. In contrast, warming strengthened the N effect on N2O fluxes in the early growing season under the absence of graminoids or shrubs, which could be attributed to the increase of available carbon and nitrogen for N2O production. It should be noted that these effects were not observed under the condition of low carbon availability. In addition, gross primary production was found as a critical control on N2O fluxes under N addition. Our findings emphasize that the interaction of abiotic (warming and elevated nitrogen deposition) and biotic factors (vegetation composition change) on N2O fluxes should be taken into account in order to project N2O fluxes in peatland ecosystems accurately.

Automated summary

Through a 5-year experiment in a peatland in Canada, it was found that climate warming mitigated the influence of nitrogen on N2O fluxes under intact vegetation, but strengthened it in the absence of graminoids or shrubs. Additionally, these effects were not observed under conditions of low carbon availability.