Rainfall reduction amplifies the stimulatory effect of nitrogen addition on N₂O emissions from a temperate forest...

Soil is a significant source of atmospheric N₂O, and soil N₂O emissions at a global scale are greatly affected by environment changes that include continuous deposition of atmospheric nitrogen and changing precipitation distribution. However, to date, field simulations of multiple factors that control the interaction between nitrogen deposition and precipitation on forest soil N₂O emissions are scarce. In this study, we conducted a 2-year continuous assessment of N₂O emissions from November 2012 to October 2014 at a nitrogen addition and rainfall reduction manipulation platform in an old broad-leaved Korean pine mixed forest at Changbai Mountain in northeastern China. We found that N₂O emissions from control plots were 1.25 ± 0.22 kg N₂O-N ha^-1 a^-1. Nitrogen addition significantly increased N₂O emissions, with the emission factor of 1.59%. A 30% reduction in rainfall decreased N₂O emissions by 17-45%. However, in combination, nitrogen addition and rainfall reduction increased N₂O emissions by 58-140%, with the emission factor of 3.19%, and had a larger promotional effect than the addition of nitrogen alone. Our results indicated that drought slightly decreases forest soil N₂O emission; however, with increasing deposition of atmospheric N in temperate forest soils, the effect of drought might become altered to increase N₂O emission.