中文关键词外源N₂O水稻土淹水厌氧N₂O消纳nosZ-I型 英文关键词exogenous N₂Opaddy soilflooding-anaerobic conditionN₂O consumptionnosZ-I

作者	单位	E-mail
郭俊丽	中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125 中南林业科技大学生命科学与技术学院, 长沙 410004	1342219040@qq.com
田美洁	湖南农业大学农学院, 长沙 410128
葛体达	中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125
魏文学	中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125
王光军	中南林业科技大学生命科学与技术学院, 长沙 410004
孙志龙	湖南省宁乡市回龙铺镇农业综合服务中心, 宁乡 410606
刘毅	中国科学院亚热带农业生态研究所亚热带农业生态过程重点实验室, 长沙 410125	liuyi@isa.ac.cn

中文摘要 稻田土壤长期的淹水厌氧环境有利于反硝化作用的进行，是导致N₂O大量排放的重要原因之一.目前，关于稻田土壤N₂O排放特征的相关研究已有不少，然而关于稻田土壤N₂O的消纳能力及相关功能微生物的应答机制尚不明确.本研究以淹水水稻土原状土柱（0~5 cm）为研究对象，在土柱底部输入外源N₂O气体，系统监测所添加外源N₂O通过土柱的浓度及关键土壤因子的动态变化特征，以及分析nosZ-I型功能种群组成的演替规律，以期揭示淹水水稻土N₂O的消纳能力及nosZ-I型功能种群的应答机制.结果表明，外源N₂O输入后约97.39%扩散进入土柱，逸散出土表的N₂O占0.72%~7.75%，达到排放高峰后被土壤继续消耗，培养192 h后外源N₂O处理比对照多消耗67.10% N₂O，N₂O消耗速率提高144.2%.同时，NH₄⁺-N、NO₃^--N和DOC分别多消耗了19.65%、16.29%和8.41%.N₂O输入192 h后nosZ-I的群落多样性没有显著差异，但是其种群组成发生显著改变：优势菌株OTU5004、OTU5065、OTU960和OTU1282（Proteobacteria）相对丰度显著提高，其中OTU5004菌株相对丰度比初始样和CK升高7.30%和4.63%，非优势菌株OTU5265（Azoarcus sp.）比初始样和CK升高0.33%和0.15%.上述结果表明，0~5 cm深度渍水水稻土壤具有很强的N₂O消耗能力，外源N₂O添加使N₂O消耗速率明显加快，提高了淹水水稻土壤对N₂O的消纳潜力，促进碳氮转化和nosZ-I群落组成变化，这将为降低大气N₂O排放提供新的参考. 英文摘要 The long-term flooding anaerobic environment in paddy soils is conducive to denitrification, which is one of the most important reasons for N₂O emissions. N₂O can be transformed to nitrogen gas (N₂) by bacteria and archaea containing nitrous oxide reductase (N₂OR) encoded by the nosZ gene, which is the only known biological pathway of N₂O consumption in soil. nosZ-I is known to be typical in denitrifying bacteria, which is one of the clades of the nosZ gene and is mainly possessed a Tat signal peptide motif. Although many researchers have studied N₂O emission characteristics of paddy soil, the capacity of N₂O consumption and the response mechanism of related functional microorganisms in paddy fields is not yet clear. To verify the effect of exogenous N₂O on N₂O consumption and nosZ-I gene, a pot trial experiment was performed under anaerobic conditions. We collected intact soil cores from flooding paddy fields at a 0-5 cm depth, and exogenous N₂O gas was input through the bottom of flooding paddy soil cores. Meanwhile, a control treatment (CK) with no additional N₂O gas was also performed. The dynamic characteristics of the added exogenous N₂O concentration through the intact soil cores, the content of inorganic nitrogen, and DOC were systematically monitored. In addition, the change in the nosZ-I population diversity and community composition were investigated by high-throughput sequencing approaches, with the purpose of revealing the N₂O uptake ability of flooded paddy soil and the response mechanism of the nosZ-I population. The results showed that 97.39% of exogenous N₂O diffused into the soil cores, and only 0.72%-7.75% of exogenous N₂O escaped from the soil surface. The N₂O released in the headspace of soil cores could continue being absorbed and consumed by the flooding soil column. In addition, 67.10% of the N₂O escaped to the headspace was consumed in exogenous N₂O treatment after 192 h of incubation, which was higher than that in CK treatment, and the N₂O consumption rate increased by 144.2% than that in CK treatment. Meanwhile, the consumption of NH₄⁺-N, NO₃^--N, and DOC consumed during exogenous N₂O addition treatment was 19.65%, 16.29%, and 8.41% higher than that in CK treatment, respectively. However, the diversity of the nosZ-I gene community had no significant difference; the community composition of nosZ-I-containing bacteria changed significantly after 192 h when exogenous N₂O was input. The abundances of OTU5004, OTU5065, OTU960, and OTU1282 (Proteobacteria) significantly increased, which were the dominant bacterial strain of nosZ-I gene on the OTU level. Compared with the initial sample and CK, the abundance of the OTU5004 strain increased by 7.3% and 4.63%, and the abundance of the OTU5265 strain (Azoarcus sp.) increased by 0.33% and 0.15%, respectively. The result indicated that the flooding paddy soil column at the soil layer of 0-5 cm has a strong N₂O absorption and consumption ability. In summary, compared with CK, the addition of exogenous N₂O significantly accelerated the N₂O consumption rate, improved the consumption potential of flooding paddy soil column, promoted carbon and nitrogen conversion, and changed nosZ-I community composition. These results would provide a new reference for reducing atmospheric N₂O emissions.

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