Graminoid Removal Reduces the Increase in N2O Fluxes Due to Nitrogen Fertilization in a Boreal Peatland

Abstract

The increase in nitrogen (N) deposition may affect nitrous oxide (N2O) emission in boreal peatlands by increasing N availability and/or altering vegetation composition. However, the effects of changes in vegetation composition (due to the increase in N deposition) on N2O emission are still unknown. Therefore, we used a factorial design, comprising the removal of plant functional groups and N fertilization to investigate their independent effects and combined effects on N2O fluxes at an ombrotrophic blanket bog in Western Newfoundland, Canada. The results reveal that N2O emission significantly increased with N fertilization. Notably, the effect of N addition on N2O fluxes was modulated by the removal of graminoids. In particular, the removal of graminoids reduced 69% of the N2O emission increases due to N fertilization in the third year of the experiment. This result suggests that the enhancement of graminoid abundance due to increases in N deposition/fertilization may dramatically increase N2O emissions in boreal peatlands leading to stronger impacts on the global climate and stratospheric ozone depletion in the future if no countermeasures to reduce reactive N emission are undertaken.