Warming reduces the increase in N₂O emission under nitrogen fertilization in a boreal peatland

Peatlands are known as N₂O sinks or low N₂O sources due to nitrogen (N) limitation. However, climate warming and N deposition can modulate this limitation, and little is known about the combinative effects of them on N₂O emission from boreal peatlands. In this study, experimental warming and N fertilization treatments were conducted at a boreal peatland in western Newfoundland, Canada. Contrary to previous studies on permafrost peatland and alpine meadows, the effect of warming treatment on N₂O flux was not detectable during the growing seasons of 2015 and 2016. The N fertilization treatment significantly increased the N₂O flux by 1.61 nmol m^-2 s^-1 due to increased N availability. Noticeably, warming reduced the effect of N fertilization treatment on N₂O flux with high significance in the middle growing season of 2015. This can be attributed to low N availability caused by stimulated vegetation growth in the warming treatment. In addition, the results showed that total nitrogen was the main control on N₂O emission under N fertilization, while dissolved organic carbon was the main driver under the combined treatment of warming and N fertilization. Due to elevated N₂O emissions under N deposition/fertilization, the contribution of N₂O to global warming and ozone depletion should not be ignored.