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.
我国亚热带地区大气氮沉降量逐年上升,对森林土壤生物地球化学循环造成严重影响。本研究设置了对照(不添加氮)、低氮(40 kg·hm-2·a-1)和高氮(80 kg·hm-2·a-1)处理,分析了亚热带米槠天然林土壤反硝化功能基因丰度和N2O排放潜势对氮沉降的响应。结果表明: 高氮处理显著降低土壤N2O排放潜势。长期(8年)氮沉降对nirS、nirK、nosZ Ⅰ和nosZ Ⅱ基因丰度均无显著影响,但nosZ Ⅰ丰度均显著高于nosZ Ⅱ丰度,表明nosZ Ⅰ在酸性森林土壤中占主导。与对照相比,高氮处理显著降低(nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ)值。(nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ)值与土壤pH值呈显著正相关。长期高氮沉降可能通过降低土壤pH值使得土壤(nirK+nirS)/(nosZ Ⅰ+nosZ Ⅱ)值下降,从而降低森林土壤N2O排放潜势。.
Keywords: N2O emission; denitrifying gene; forest soil; nitrogen addition.