KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 西北干旱区棉田和草原生态系统 N2O 产排的关键过程和微生物驱动机制研究 | |
| Alternative Title | Study on Key Processes and Microbial Mechanisms of Nitrous Oxide Emissions from Cotton Fields and Grassland Ecosystems in Arid Region of Northwest China |
| 尹明远 | |
| Subtype | 博士 |
| Thesis Advisor | 高霄鹏 ; 曾凡江 |
| 2020-06-30 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 北京 |
| Degree Discipline | 理学博士 |
| Keyword | 氧化亚氮 硝化活性 反硝化活性 功能基因丰度 微生物群落结构 剖面 N2O 浓度 土壤冻融 施肥 放牧 Nitrous oxide Denitrifying enzyme activity Nitrifying enzyme activity Functional genes Bacterial community structure Profile N2O concentration Spring-thaw Grazing Nitrogen fertilizer |
| Abstract | N2O 是最重要的温室气体之一， 其约 70-80%的人为排放来自于农业土壤尤其是农田和草地土壤，主要与农业生产过程中的氮肥施用（包括化肥和有机肥）和放牧管理措施有关。新疆膜下滴灌棉田和昆仑山北坡高山草地是我国西北干旱区主要的农田和草原生态系统，然而关于这两种生态系统生长季和冻融期土壤N2O 产排特征及其关键调控因子，尤其是不同氮肥管理措施和放牧强度对 N2O排放影响及其微生物机理的研究尚不多见。 理解 N2O 产排关键过程（施肥和冻融）的微生物调控机制对减少 N2O 排放和实现绿色农业至关重要。因此，本研究以南北疆滴灌棉田和南疆昆仑山北坡高山草地为研究对象，结合田间定位试验和室内实验室分析，利用原位硅胶管和静态箱方法连续监测土壤剖面 N2O 浓度和地表排放，应用高通量测序和定量 PCR 监测 N2O 产生相关微生物丰度和群落结构，系统研究了西北干旱区膜下滴灌棉田生长季和冻融期土壤 N2O 排放特征及其微生物驱动机制。主要研究内容包括： 1）滴灌棉田土壤冻融期 N2O 排放的生物学机制； 2）施用化肥或有机肥对滴灌棉田 N2O 产排的影响及其与相关功能基因的关系； 3） 不同放牧强度对昆仑山北坡高山草地 N2O 产排特征的影响及其与环境因子包括气候、土壤和相关微生物的关系； 4）氮（N）磷（P）养分添加对草地 N2O 排放影响的微生物机制。主要研究结果总结如下：1）滴灌棉田土壤冻融期的 N2O 排放占全年排放的近 40%，主要以反硝化作用下的新产生机制为主；干旱区农田在越冬期土壤温湿度低，不利于 N2O 产生和冰冻层的形成，因此物理释放机制可忽略不计；土壤融化阶段的反硝化强度和N2O 排放主要与土壤温度和土壤孔隙含水率（WFPS）的增加有关，而与 narG、nirS、 nirK 和 nosZ 等反硝化菌的丰度变化无显著相关；棉田生育期氮肥处理对冻融期 N2O 排放影响不大，主要与长期滴灌耕作造成硝态氮在表层土壤的累积较高有关。2）与不施肥对照和尿素处理相比，施加有机肥显著增加了 narG， nirK， nirS和 nosZ-型反硝化菌的丰度，并显著影响了土壤细菌微生物的群落结构。 有机肥处理较尿素处理明显增加了反硝化酶活性，而对硝化活性无显著影响；棉田生长季 N2O 排放与反硝化酶活性、以及 narG， nirK 和 nosZ 基因丰度存在显著正相关关系。这些结果表明有机肥增加南疆滴灌棉田土壤 N2O 排放，主要是通过增加土壤有机碳，进一步增加了土壤反硝化相关功能基因的丰度，从而反硝化活性增强，促进 N2O 产排。3） 南疆昆仑山北坡高山草地生态系统的 N2O 排放量整体较低，与封牧处理相比，重度和中度放牧显著增加了 N2O 排放；不同放牧强度处理下草地土壤 N2O排放速率与相关硝化和反硝化功能基因的丰度和活性无显著相关，而更受到土壤性质包括有机碳含量和温湿度的影响。 放牧通过改变土壤 C、 N 含量， 从而改变土壤微生物群落 β 多样性。 同时发现， 不同放牧强度处理下土壤剖面 N2O 的浓度和累积量无显著差异。这些研究结果表明制定合理的放牧管理措施以减少草地N2O 排放并维持畜牧业生产的重要性。4） 与单施氮肥相比，氮磷同时添加不但提高了草地生产力，维持了土壤微生物群落的多样性，而且显著减少了 N2O 排放；氮添加增加昆仑山北坡高山草地土壤 N2O 排放，主要是通过增加土壤硝化相关功能基因的丰度，从而增加硝化活性，促进 N2O 产排； N、 P 同时添加减少 N2O 排放，可能是由于增加了草地生产力，进一步增加了其对氮的吸收，进而减少了土壤无机氮的有效性，降低硝化和反硝化强度。 |
| Other Abstract | Nitrous oxide (N2O) is one of the most important greenhouses. About 70-80% ofanthropogenic N2O emissions are associated with agricultural soils, particularlygrassland and farmland soils, which are mainly attributed to applications of nitrogen(N) fertilizers (including synthetic fertilizer and manure) and grazing practices inagricultural production. Cotton production under drip fertigation system is widelyused in arid northwestern China. In addition, the alpine grassland of Kunlun Mountainin Xinjiang province of China plays a key role in local livestock production of sheepand cattle. However, few studies have investigated N2O emissions over the growingand non-growing seasons and their microbial mechanisms for these two importantecosystems, in response to grazing intensity or N fertilizer management.Understanding the microbial regulation mechanisms of the two key processes of N2Oproduction and emissions (i.e. fertilization application and freeze-thaw) is essential toreduce N2O emissions and achieve green agriculture. Therefore, under both field andlaboratory conditions, this study intensityly investigated N2O emissions and itsassociated microbial mechanisms for the two ecosytemes including drip-fertigatedcotton field and the alpine grassland of Kunlun Mountain in Xinjiang Province. Themodified in-situ equilibrium silicon gas sampler and static-vented chamber techniquewere used for determination of N2O concentrations in soil profile and surfaceemissions, respectively. High-throughput sequencing and real time quantitative PCRwere used to monitor the temperal changes of N2O-producing related microorganismabundance and community structure over the gorwing and non-growing periods. Thisstudy included 1) microbial mechanisms of N2O emissions during spring-thaw in thedrip-fertigated cotton fields; 2) effect of synthetic fertilizer or manure application onN2O production and emissions, in relation to N2O producing functional genes; 3)effect of grazing intensity on dynamic changes of N2O emissions from alpinegrassland of Kunlun Mountain, in relation to environmental factors of climate, soil and microbies; 4) microbial machanims of N2O emissions from grassland as affectedby nutrient additions of nitrogen and phosphorus. The main results are summarized asfollowings.1) N2O emissions during freeze-thaw period accounted for approximately 40% ofthe annual N2O emissions and were mostly due to the nove N2O production bydenitrification rather than physical release of N2O in the soil over winter. The low soilwater availability over the winter period hindered the production of N2O over winter,as well as the formation of an ice layer to trap N2O gas. The daily N2O flux rateduring spring-thaw correlated positively with the increasing soil temperature,water-filled pore space, and denitrifying enzyme activity, but not with the abundanceof AOA, AOB, narG, nirS, nirK and nosZ. Fertilizer treatments in the previousgrowing season did not affect spring-thaw N2O emissions, which was associated withthe high accumulation of soil residual NO3--N availability under drip-fertigatedconditions.2) Compared with the unfertilized control and urea, manure applicationsignificantly increased the copy number of narG， nirK， nirS and nosZ-denitrifier, andchanged soil microbial community beta diversity. Manure significantly increaseddenitrifying enzyme activity (DEA) compared to urea treatment, but did not affectnitrifying enzyme activity (NEA). Growing season cumulative N2O emissions wereassociated with denitrifying enzyme activities, narG and nosZ gene abundances.These results demonstrated that enhanced N2O emissions by manure underdrip-irrigated condition were mainly attributed to the increased abundance of narGand nosZ-type denitrifier genes, and thus an increased DEA due to the enhancementof organic C availability.3) The N2O emissions from the alpine grassland on Kunlun Mountain weregenerally low. Compared to none-grazing, light and intensive grazing significantincreased N2O emissions. Grazing enhanced N2O emission was not related with soilprofile N2O concentration and accumulation. Daily N2O flux rate correlated positivelywith soil temperature, moisture, and concentrations of DOC but not with theabundance and activity of the target nitrifiers and denitrifiers, suggesting that soil environmental factors, rather than changes in the abundance of the functional genedetermined N2O emissions from this alpine grassland soil. Grazing exerted asignificant impact on the composition of soil bacterial community beta diversitythrough affecting soil availability of nitrogen and carbon. These results highlight theimportance of establishing a proper grazing intensity to reduce N2O emissions fromthe degraded grassland while maintaining productivity for livestock.4) The simultaneous addition of N and P nutrients deceased N2O emissions,maintained soil microbial diversity, and improved growth and productivity of theplant, compared with N addition alone in the alpine grassland on Kunlun Mountain.The increased N2O emission by N addition was attributed to the increased nitrificationactivity (NEA) by enhancing the abundance of AOB and Nitrobacter-like nxrA. Thereduction of N2O emission by the simutaneous addition of N and P was associatedwith the increasing productivity, which further increased plant N uptake and thusreduced soil inorganic N availability for nitrification and denitrificaiton. |
| Subject Area | 生态学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/15402 |
| Collection | 中国科学院新疆生态与地理研究所 研究系统 |
| Affiliation | 中国科学院新疆生态与地理研究所 |
| First Author Affilication | 中国科学院新疆生态与地理研究所 |
| Recommended Citation GB/T 7714 | 尹明远. 西北干旱区棉田和草原生态系统 N2O 产排的关键过程和微生物驱动机制研究[D]. 北京. 中国科学院大学,2020. |
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