[Simulated nitrogen deposition reduces potential nitrous oxide emissions in a natural Castanopsis carlesii forest...

The reactive nitrogen deposition in subtropical region of China has been increasing annually, which affects biogeochemical processes in forest soils. In this study, three treatments were established, including control (no N addition, CK), low nitrogen deposition (40 kg·hm^-2·a^-1, LN), and high nitrogen deposition (80 kg·hm^-2·a^-1, HN) to study the response of denitrifying functional genes and potential N₂O emissions to simulated nitrogen deposition in the soils of a natural Castanopsis carlesii forest. Results showed that HN significantly decreased soil potential N₂O emission, while 8-year nitrogen deposition did not affect the abundances of nirS, nirK, nosZ Ⅰ and nosZ Ⅱ. However, the abundance of nosZ Ⅰwas significantly higher than nosZ Ⅱ in all the treatments, indicating that nosZ Ⅰ dominated over nosZ Ⅱ in the acidic soils. HN significantly decreased the ratio of (nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ), which was positively correlated with soil pH. The results suggested that long-term high nitrogen deposition reduced soil pH and the abundance ratio of (nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ), which subsequently reduced the potential N₂O emission.