【作者】 张敏；

【导师】 任卫波；

【作者基本信息】 内蒙古大学 ， 生态学， 2024， 硕士

【摘要】 甲烷（CH₄）是全球第二大温室气体,对温室效应的贡献率高达20%-40%。内蒙古半干旱草地是重要的甲烷汇,土壤中好氧甲烷氧化菌以甲烷为原料氧化形成二氧化碳,是消耗大气甲烷的唯一生物汇,对缓解温室效应有重要意义。本文以内蒙古典型草原过度放牧（Overgrazing-OG）和围封（No grazing-NG）土壤为研究对象,结合野外取样和室内培养实验,探究过度放牧对典型草原优势植物、土壤性状及酶活性的影响,分析过度放牧及环境因子（温度,水分,p H和氮添加）对土壤甲烷氧化影响的耦合作用;并利用宏基因组测序和Pmo A功能基因定量PCR技术,解析过度放牧及其环境因子驱动下草地土壤微生物群落和甲烷氧化菌群落变化特征,以期从微观角度阐明放牧系统引起甲烷动态变化的原因及影响因子。主要结论如下:（1）土层深度、温度、含水量对典型草原土壤甲烷氧化量、甲烷氧化效率有显著影响。0-10 cm土壤、28℃、30%土壤含水量条件下草地土壤甲烷氧化量和氧化速率最高;（2）与围封相比,过度放牧显著降低了土壤甲烷氧化量,甲烷氧化量、甲烷氧化速率与土壤深度、温度和p H值存在耦合作用;（3）与围封相比,过度放牧显著降低了与甲烷氧化相关的α-变形菌纲、β-变形菌纲、γ-变形菌纲和δ-变形菌纲细菌的相对丰度及甲烷氧化菌的Pmo A基因丰度;甲烷氧化量和甲烷氧化速率与Pmo A基因丰度呈正相关;（4）甲基杆菌属（Methylobacterium）、甲基暖菌属（Methylocaldum）、甲基帽菌属（Methylocapsa）甲基八叠球菌属（Methylosarcina）等四个与甲烷氧化相关的类群表现出对过度放牧和培养后不同的响应趋势;过度放牧引起的土壤含水量变化和土壤性质变化是造成甲烷氧化菌群落变化的重要原因,本研究为过度放牧后土壤甲烷氧化潜力和甲烷氧化菌群落组成的变化提供了新的证据。更多还原

【Abstract】 Methane(CH4)is the world’s second largest greenhouse gas,contributing 20%to 40% of the greenhouse effect.The semi-arid grassland in Inner Mongolia is an important methane sink,and the aerobic methane oxidizing bacteria in the soil oxidize methane to form carbon dioxide,which is the only biological sink that consumes atmospheric methane,which is of great significance for alleviating the greenhouse effect.In this paper,overgrazing(OG)and no grazing(NG)soil samples of typical grasslands in Inner Mongolia were taken as research objects,combined with field sampling and indoor culture experiments,to explore the effects of overgrazing on dominant plants,soil properties and enzyme activities of typical steppe grasslands.The coupling effects of overgrazing and environmental factors(temperature,moisture,p H and nitrogen addition)on soil methane oxidation were analyzed.The changes of soil microbial community and methane oxidizing bacteria community in grassland driven by overgrazing and environmental factors were analyzed using metagenomic sequencing and quantitative PCR technology of Pmo A functional gene,in order to elucidate the causes and influencing factors of dynamic changes of methane caused by grazing system.The main conclusions are as follows:(1)Soil depth,temperature and water content have significant effects on methane oxidation and methane oxidation efficiency of typical steppe grassland soil.The highest methane oxidation amount and oxidation rate of grassland soil were obtained under the conditions of 0-10 cm soil,28℃ and 30% soil water content.(2)Compared with enclosure,overgrazing significantly reduced soil methane oxidation.Methane oxidation and methane oxidation rate were coupled with soil depth,temperature and p H value.(3)Compared with containment,overgrazing significantly decreased the relative abundance of α-Proteobacteria,β-Proteobacteria,γ-proteobacteria and δ-proteobacteria associated with methane oxidation,as well as the Pmo A gene abundance of methane oxidation bacteria.The amount and rate of methane oxidation were positively correlated with the abundance of Pmo A gene.(4)Methylobacterium,Methylocaldum,Methylocapsa,Methylosarcina and other groups related to methane oxidation showed different response trends to overgrazing and culture.The changes of soil water content and soil properties caused by overgrazing are important reasons for the changes of methane-oxidation bacteria community.This study provides new evidence for the changes of soil methane oxidation potential and methane-oxidation bacteria community composition after overgrazing.更多还原