No effect of warming and watering on soil nitrous oxide fluxes in a temperate sitka spruce forest ecosystem

Soil fluxes of nitrous oxide (N2O) play an important role in the global greenhouse gas budget. However, the response of soil N2O emissions to climate change in temperate forest plantations is not yet well understood. In this study, we assessed the responses of soil N2O fluxes to experimental warming with or without water addition, using a replicated in situ heating (~2°C above ambient) and water addition (170 mm) experiment in a temperate Sitka spruce plantation forest over the period 2014–2016. We found that seasonal fluxes of N2O during the year were highly variable, ranging from net uptake to net emissions. Seasonal variations in soil N2O fluxes were not correlated with either soil temperature or soil moisture. In addition, none of the individual warming/watering treatments, or their interactions, had significant effects on soil N2O fluxes and N-related soil properties. Overall, our results suggest that despite future increases in temperature, soil N2O emission may remain largely unchanged in many temperate forest ecosystems that are often N-limited.