| 稻田微氧层和还原层土壤有机碳矿化对氮素添加的响应 |
| 摘要点击 2563 全文点击 889 投稿时间：2022-09-30 修订日期：2022-12-27 |
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| 中文关键词 稻田土壤 微氧层 还原层 土壤有机碳 水稻秸秆 氮素添加 磷脂脂肪酸(PLFAs) |
| 英文关键词 paddy soil micro-aerobic layers anaerobic layers soil organic carbon rice straw nitrogen addition phospholipid fatty acid(PLFAs) |
| 作者 | 单位 | E-mail | | 毛婉琼 | 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
中国科学院大学, 北京 100049 | maowanqiong20@mails.ucas.ac.cn | | 夏银行 | 湖南农业大学资源环境学院, 长沙 410128 | | | 马冲 | 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
中国科学院大学, 北京 100049 | | | 朱光旭 | 贵阳学院生物与环境工程学院, 贵阳 550005 | | | 王忠诚 | 中南林业科技大学林学院, 长沙 410004 | | | 涂强 | 赫姆霍兹抗感染国际实验室, 山东大学赫姆霍兹生物技术研究所, 微生物技术国家重点实验室, 青岛 266237 | | | 陈香碧 | 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 | xbchen@isa.ac.cn | | 吴金水 | 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 | | | 苏以荣 | 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 | |
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| 中文摘要 |
| 田间条件下，淹水稻田由于上覆水中溶解氧的扩散作用，使其表层土壤存在约1 cm厚的微氧层，这个特殊层次中碳氮转化的特征尚未明晰.以亚热带典型稻田土壤为对象，采用100 d室内模拟培养试验，结合13C稳定同位素示踪和磷脂脂肪酸（PLFA）分析技术，研究稻田土壤微氧层（0~1 cm）和还原层（1~5 cm）外源新鲜有机碳（13C-水稻秸秆）和原有土壤有机碳矿化对氮肥施用［（NH4）2 SO4］的响应规律及其微生物过程.结果表明，氮素添加使土壤总CO2和13C-CO2累积排放量分别提高11.4%和12.3%；培养结束时，氮素添加下还原层比微氧层土壤总有机碳含量和13C回收率分别降低2.4%和9.2%.培养前期（5 d），氮素添加提高还原层微生物总PLFAs，且细菌和真菌PLFAs响应一致，但对微氧层微生物丰度无显著影响；氮素添加对微氧层和还原层总13C-PLFAs丰度均无显著影响，但13C标记细菌和真菌丰度显著降低.培养后期（100 d），氮素添加对微生物总PLFAs的影响与前期一致；氮素添加显著增加还原层13C标记总量及细菌和真菌PLFAs含量，但对微氧层总13C-PLFAs丰度无显著影响.培养期间，还原层土壤铵态氮含量高于微氧层.因此，施加氮素提高了稻田还原层土壤微生物活性，可能是由于还原层土壤具有更高的铵态氮，而大部分微生物偏好利用铵态氮，使还原层微生物生长和活性强于微氧层，进而加速还原层有机碳的微生物利用和分解；与之对应，微氧层土壤由于氨氧化作用，速效氮更多以硝态氮形态存在，因偏好利用硝态氮的微生物缺乏，限制了微氧层有机碳的微生物代谢.综上，氮肥施用增强稻田土壤有机碳矿化损失，但以微氧层响应弱于还原层，提示微氧层对土壤有机碳有一定保护作用.本研究强调了稻田土体的非均一性，其微氧层碳氮转化的特殊性不可忽视，研究结果对优化稻田种植系统氮肥施用形态和方法有一定启示意义. |
| 英文摘要 |
| In field conditions, a micro-aerobic layer with 1 cm thickness exists on the surface layer of paddy soil owing to the diffusion of dissolved oxygen via flooding water. However, the particularity of carbon and nitrogen transformation in this specific soil layer is not clear. A typical subtropical paddy soil was collected and incubated with13C-labelled rice straw for 100 days. The responses of exogenous fresh organic carbon(13C-rice straw) and original soil organic carbon mineralization to nitrogen fertilizer addition[(NH4)2SO4]in the micro-aerobic layer(0-1 cm) and anaerobic layer(1-5 cm) of paddy soil and their microbial processes were analyzed based on the analysis of 13C incorporation into phospholipid fatty acid(13C-PLFAs). Nitrogen addition promoted the total CO2 and 13C-CO2 emission from paddy soil by 11.4% and 12.3%, respectively. At the end of incubation, with the addition of nitrogen, the total soil organic carbon (SOC) and13C-recovery rate from rice straw in the anaerobic layer were 2.4% and 9.2% lower than those in the corresponding micro-aerobic layer, respectively. At the early stage(5 days), nitrogen addition increased the total microbial PLFAs in the anaerobic layer with a consistent response of bacterial and fungal PLFAs. However, there was no significant effect from nitrogen on microbial abundance in the micro-aerobic layer. Nitrogen addition had no significant impact on the abundance of total 13C-PLFAs in the micro-aerobic and anaerobic layers, but the abundance of 13C-PLFAs for bacteria and fungi in the micro-aerobic layer was decreased dramatically. At the late stage(100 days), the effect of nitrogen addition on microbial PLFAs was consistent with that at the early stage. The abundances of total, bacterial, and fungal 13C-PLFAs were remarkably increased in the anaerobic layer. However, the abundance of 13C-PLFAs in the micro-aerobic layer showed no significant response to nitrogen addition. During the incubation, the content of NH4+-N in the anaerobic soil layer was higher than that in the micro-aerobic soil layer. This indicates that nitrogen addition increased microbial activity in the anaerobic soil layer caused by the higher NH4+-N concentration, as majority of microorganisms preferred to use NH4+-N. Consequently, the microbial utilization and decomposition of organic carbon in the anaerobic soil layer were accelerated. By contrast, richer available N existed in the form of NO3--N in the micro-aerobic soil layer owing to the ammoxidation process. Thus, the shortage of NO3--N preference microorganisms in the paddy soil environment prohibited the microbial metabolism of organic carbon in the micro-aerobic layer. As a whole, nitrogen fertilization enhanced organic carbon loss via microbial mineralization in paddy soil with a weaker effect in the micro-aerobic layer than that in the anaerobic layer, indicating the limited microbial metabolic activity in the surface micro-aerobic layer could protect the organic carbon stabilization in paddy soil. This study emphasizes the heterogeneity of paddy soil and its significant particularity of carbon and nitrogen transformation in micro-aerobic layers. Consequently, this study has implications for optimizing the forms and method for the application of nitrogen fertilizer in paddy cropping systems. |
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