| 摘 要： |
Clarifying responses of nitrification-derived N2O (N2On) emission and denitrification-derived N2O (N2Od) emission to increasing nitrogen (N) deposition and the corresponding control factors help to better understand and predict the soil total N2O (N2OT) emission in the context of global change. However, these have not been well studied, particularly at different soil layers. Here, we measured those different N2O fluxes with laboratory in-cubation and the corresponding soil abiotic and biotic properties along a field N addition gradient at three soil depths in an alpine meadow. The results show that, with increasing N addition, both N2OT and N2On emissions linearly increased, but N2Od emission linearly decreased at all soil depths (p < 0.05). The N2On emission was correlated neither with the nitrification rate nor the abundance of nitrifier genes, but was positively correlated with the proportion of N2On being emitted from nitrification (PN2On), which became larger with N enrichment (p < 0.05). The N2Od emission was positively correlated with the abundance of narG and nirS genes, which decreased with N enrichment (p < 0.05). These results reveal that the N2On and N2Od emissions responded differently to increasing N deposition in both topsoil (0-10 cm) and subsoil (10-20 and 20-40 cm), and that the increase in N2On emission was responsible for the higher N2OT emission with N enrichment. These findings extend the current understanding of the mechanism underlying increased N2OT emission with N enrichment, as previous studies have ignored the possibility of a depressed N transformation process derived N2O emission. The dynamics of PN2On and the abundance of narG and nirS in both topsoil and subsoil should be noted to better predict N2On and N2Od emissions, and therefore, N2OT emission in the context of enhanced N deposition. |
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