pH对土壤硝化作用和氨氧化微生物的影响及其作用机理
文献类型：学位论文
| 作者 | 张苗苗 |
| 学位类别 | 硕士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 张丽梅 |
| 关键词 | 酸性土壤 pH 矿化作用 硝化作用 氨氧化细菌 氨氧化古菌 氧化钙 acidic soils pH mineralization nitrification ammonia-oxidizing bacteria ammonia-oxidizing archaea liming |
| 其他题名 | The effects of pH on nitrification and ammonia oxidizers in soils and the underlying mechanisms |
| 学位专业 | 生物工程 |
| 中文摘要 | 土壤pH是影响硝化作用和氨氧化微生物多样性分布及功能活性的主要因子，除直接影响硝化作用的底物NH3浓度及功能微生物（氨氧化微生物）外，pH还通过影响氮矿化速率来间接影响土壤硝化作用，使得pH与硝化作用的关系变得更为复杂。酸性土壤（pH<5.5）在我国分布面积广泛，是我国热带亚热带经济作物如茶树、林木、果树和粮食作物的重要产地。近几十年来，由于化学氮肥的过量施用及氮沉降加剧，我国农田土壤的酸化程度逐渐增加，酸化面积也不断增加。研究酸性土壤的硝化作用机理，对提高酸性土壤氮肥利用效率和减轻酸性土壤硝化作用的负面环境效应具有重要的理论和实践指导意义。因此，本研究以代表不同pH梯度的一系列酸性土壤为研究对象，调查了土壤硝化作用与pH和土壤矿化作用之间的关系，并以湖南祁阳施肥定位实验站长期施用不同化学肥料和施用石灰改良的农田土壤为研究对象，研究了在酸性土壤中矿化速率及硝化活性的关系，以及添加氧化钙（CaO）所引起的pH改变对酸性土壤硝化作用以及氨氧化微生物的丰度及群落结构的影响，得到以下主要结果： 1. 对8个代表不同pH梯度（pH(KCl) 3.66~6.72）的土壤进行微宇宙培养研究，结果表明，在30天的培养期内，土壤的矿化速率、硝化速率均与土壤pH无显著相关关系，但硝化速率与土壤NH4+-N浓度、矿化速率显著正相关，说明在这些pH较低的土壤中，pH并不是影响其矿化及硝化活性的主要或唯一因素。酸性土壤中由于大部分NH3离子化成为NH4+，能提供给氨氧化过程所需的底物较少，而通过氮的矿化作用所释放的NH3可为土壤持续长时间提供低水平稳定的NH3，是土壤氨氧化作用底物NH3的主要来源。 2. 以湖南祁阳施肥定位实验站长期施用不同化学肥料和施用石灰改良的酸性土壤为研究对象，探讨了土壤氨氧化微生物及硝化作用对不同施肥处理及氧化钙调节的响应。研究结果表明，长期施用化学氮肥导致酸性土壤pH（pH(KCl) 3.35~3.47）和硝化潜势（0.02~0.14 μg NO2--N g-1 soil h-1）进一步降低，而添加CaO后土壤酸化得以缓解（pH(KCl) 4.10~4.46），土壤硝化潜势（0.22~0.34μg NO2--N g-1 soil h-1）显著增加。同时，添加CaO处理的土壤中，AOA的数量降低而AOB的数量明显增加，且添加CaO处理对氨氧化古菌（AOA）的群落结构无明显影响，但对AOB的群落组成产生显著影响，在仅施加无机氮肥处理的土壤中，AOB的优势类群为Cluster 10，添加CaO处理土壤中Cluster 3a.1的相对丰度显著增加，AOB的优势类群变为Cluster 10和3a.1，表明这些类群对CaO添加产生了明显响应，对添加CaO后土壤硝化作用的增加有重要贡献。但室内短期模拟添加不同浓度CaO的实验表明，AOA和AOB的数量和群落组成均对添加CaO处理产生迅速响应，AOB的数量在培养至第7天时随CaO浓度增加而增加，之后逐渐降低，而AOA的数量在培养至第7天时明显降低，而后逐步恢复。AOA和AOB的群落结构随CaO加入也发生明显变化，并随培养时间增加又逐步恢复。这些结果表明，虽然AOA因自身的生理及遗传特征更适应在酸性土壤硝化作用中发挥作用，而AOB则在酸性土壤中表现为功能冗余，但当土壤pH受到扰动而升高后，AOA和AOB均对环境条件变化迅速做出响应，共同驱动着酸性土壤的硝化作用。另外，AOA和AOB对添加CaO的响应均具有长期和短期时间梯度上的差异性。 |
| 英文摘要 | Increasing evidence have demonstrated that pH is one of the most important factors influencing the nitrification activity and the distribution of bacterial and archaeal ammonia oxidizer (AOB and AOA), and that AOA plays more important role in nitrification of acidic soils. Soil pH also may affect nitrification process indirectly through influencing the mineralization of nitrogen. Acidic soils (pH<5.5) is widely spread in China and is ecnomicly important in agriculture and forestry production. During the past decades, due to the large increases in the use of chemical N fertilizers, agricultural soils were acidified further across China, which further led to the mobilization of potentially toxic metals such aluminum (Al) and manganese (Mn) and the decrease of crop yield in acidic soils. In this study, the effects of pH on nitrogen mineralization and nitrification, and the effect of liming on nitrification and ammonia oxidizers in acidic soils were investigated using molecular ecology methods, including Polymerase Chain Reaction (PCR), Real-time PCR, denaturing gradient gel electrophoresis (DGGE), clone library and sequencing. The main findings of the work are described as follows: 1. A series of acidic soils sampled from Chongqing, Changbai Mountain and Yunnan Province were incubated in soil microcosms for 30 days. No significant correlation between the soil pH and mineralization/nitrification was observed during the microcosm incubation, while nitrification in these acidic soils was significantly and positively correlated with the concentration of ammonium and mineralization. These results indicated that pH was not the main factor influencing nitrification in these acidic soils. Ammonia released from the ionic equilibrium NH3/NH4+ and mineralization supplied the substrate of ammonia oxidation in soils mainly. However, ammonia availability is highly pH dependent and exponentially declined with decreasing pH. Nitrogen mineralization from organic materials supplied ammonia at a low level continuously and was the main substrate resource for autotrophic ammonia oxidizers in acidic soils. 2. The effects of long-term N fertilization practices and liming on nitrification and ammonia oxidizers in an long-term field trial in acidic soils were investigated, and the results showed that N fertilizers application decreased soil pH (pH(KCl) 3.35~3.47) and potential nitrification rate (PNR) (0.02~0.14 μg NO2--N g-1 soil h-1)further, compared with the study conducted 7 years ago, while 2 years liming alleviated soil acidification (pH(KCl) 4.10~4.46) and increased PNR (0.22~0.34μg NO2--N g-1 soil h-1) significantly. There was significantly positive correlation between soil pH and PNR, which meant the increase of pH had positive effects on nitrification in acidic soils. The abundance of AOA is significantly higher than their counterpart in soils received different chemical N fertilizers. The ratio of AOA and AOB abundance ranged between 10.9 and 44.3. Two years after lime was applied into the N fertilizers treatment plots as a soil conditioner, the abundance of AOA decreased to a certain degree but AOB increased significantly compared with their corresponding fertilization treatments without liming, resulting the ratio of AOA and AOB abundance decreased to 0.83~1.94. Meanwhile, liming showed no significant influence on the community structure of AOA, but significantly changed the community structure of AOB. Cluster 10 was dominant AOB group in inorganic N fertilizers treatment without liming, while the relative abundance of Cluster 3a.1 was significantly increased in their corresponding treatment with liming. All these indicated that even the activity and abundance of AOA generally dominated over AOB in acidic soils, both AOA and AOB responded to the disturbance in acidic soils actively based on their niche differentiation and functioned alternatively in nitrification in acidic soils. Additionally, ammonia oxidizers responded to liming differently between short-term and long-term. |
| 公开日期 | 2015-07-08 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/15604]  |
| 专题 | 生态环境研究中心_土壤环境科学实验室 |
| 推荐引用方式 GB/T 7714 | 张苗苗. pH对土壤硝化作用和氨氧化微生物的影响及其作用机理[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：生态环境研究中心
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