土壤水分对土壤产生气态氮的厌氧微生物过程的影响

气态氮一氧化氮(NO)、氧化亚氮(N₂O)和氮气(N₂)]的释放是土壤氮损失的一种重要途径。硝化和反硝化作用是土壤气态氮损失的主要微生物过程,但是异养硝化作用、共反硝化作用和厌氧氨氧化过程对土壤气态氮损失的贡献尚不清楚。本研究利用¹⁵N标记和配对法,结合硝化抑制剂双氰胺(DCD),通过土壤培养试验来量化厌氧条件下各种微生物过程对NO、N₂O和N₂产生的贡献。结果表明: 在厌氧条件下培养24 h后,土壤孔隙含水率为65%时,3种气体总的¹⁵N回收率最高,占加入¹⁵N总量的20.0%。反硝化过程对NO、N₂O和N₂产生的贡献率分别为49.9%～94.1%、29.0%～84.7%和58.2%～85.8%,是产生3种气体的主要过程。异养硝化过程也是产生NO和N₂O的重要过程,特别是在土壤孔隙含水率很低时(10%)对两种气体产生的贡献率分别为50.1%和42.8%。,共反硝化过程对N₂O产生的贡献率为10.6%～30.7%,共反硝化和厌氧氨氧化过程对N₂产生的总贡献率为14.2%～41.8%,表明共反硝化过程在N₂O和N₂产生中的作用不可忽视。¹⁵N标记和配对法是区分气态氮损失的各种微生物过程的有效手段。

Effects of soil moisture on microbial processes of soil nitrogen gases production under anaerobic conditions

Gaseous nitrogen (N) emission nitric oxide (NO), nitrous oxide (N₂O), and nitrogen (N₂)] is an important pathway of soil N loss. Nitrification and denitrification are the main processes of gaseous N production in soil. However, the contribution of heterotrophic nitrification, co-denitrification, and anammox to gaseous N production remains uncertain. In a laboratory soil incubation experiment, we used the ¹⁵N labelling and pairing technique, combining the nitrification inhibitor dicyandiamide (DCD), to quantify the contribution of different microbial processes to soil NO, N₂O and N₂ production under anaerobic conditions. The results showed that after 24 h anaerobic incubation, the highest total ¹⁵N recovery of three gases occurred at 65% water filled pore space (WFPS), accounting for 20.0% of total added ¹⁵N. Denitrification contributed 49.9%-94.1%, 29.0%-84.7%, and 58.2%-85.8% to the production of NO, N₂O and N₂ respectively, suggesting that denitrification was the predominant process of those three N gases emission. Heterotrophic nitrification was an important pathway of NO and N₂O production, particularly at conditions with low soil water content (10% WFPS), with its contribution to those two N gases production being 50.1% and 42.8%, respectively. Co-denitrification contributed 10.6%-30.7% of N₂O production. For N₂ production, the total contribution of co-denitrification and anammox was 14.2%-41.8%. The role of co-denitrification can not be ignored for N₂O and N₂ production. Our results demonstrated that the ¹⁵N labelling and pairing technique is a promising tool to quantify the contribution of different microbial processes to gaseous N loss.