Knowledge Resource Center for Ecological Environment in Arid Area
| 模拟全球变化对三种草原土壤碳氮循环微生物的影响 | |
| 其他题名 | Effects of simulated global change on soil microbial groups involved in C and N cycling in three types grasslands |
| 孙翼飞 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 贺纪正 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 草原生态系统在涵养水源、防风固沙、水土保持、调节气候、维持生物多样性等方面发挥着不可替代的作用，是我国重要的生态屏障，在关键生命要素循环（碳、氮循环）中起重要作用。由于全球变化（如大气氮沉降、降水格局改变、土地利用方式改变）的影响，草原生态系统生产力下降，其结构和生态功能也受到显著影响。围绕全球变化对地上生态过程的影响已开展了大量研究，但地下过程，尤其是土壤功能微生物对全球变化的响应机制尚不明确。全球变化对土壤碳氮功能微生物影响的研究多集中于单一驱动因子对单一生态过程或单一生态系统的影响，且忽略了其在地上-地下生态系统中的重要调节作用。因此，本研究沿纬度梯度选取了我国三种不同类型的草原生态系统（典型草原、荒漠草原、高寒草甸），通过长期野外控制试验，针对不同的草原类型，选取相应的驱动因子，典型草原与高寒草甸草原分别以割草与施氮、割草与水位下降构建试验平台，荒漠草原中设置了两个试验平台，分别为不同放牧强度试验，以及施氮与改变降水交互试验。采用了实时定量PCR技术、限制性末端片段长度多态性以及克隆文库技术，来探索全球变化对不同草原类型土壤碳氮循环过程及碳氮功能微生物的影响。论文的主要研究内容与成果如下：（1）对于北方温带草原（典型草原与荒漠草原），施氮均显著降低了土壤pH；土壤硝态氮含量在施氮与增雨处理中均显著增加；不同的土地利用方式（放牧和割草）对于土壤可利用性氮影响有所差异，割草显著降低土壤硝态氮含量，对铵态氮含量影响不显著，而放牧显著增加了铵态氮含量，对硝态氮含量影响不显著。在高寒草甸草原中，水位下降与割草均显著增加土壤pH，降低土壤异养呼吸，且二者对土壤pH和硝态氮具有明显的交互作用。（2）对于北方温带草原（典型草原与荒漠草原），施氮均显著增加了AOB-amoA基因丰度。在高寒草甸草原中，水位下降和割草对氨氧化微生物与反硝化细菌基因丰度无显著影响，但AOB-amoA基因相对丰度对割草处理响应显著。施氮显著增加了典型草原固碳基因cbbL的基因丰度，且割草与施氮对其具有显著的交互作用。土壤含水量、土壤pH及可利用性氮含量的变化是影响碳氮功能微生物群落组成的主要因子。（3）土壤氨氧化和反硝化微生物在地上-地下生态系统中起着重要的调节作用。结构方程模型结果表明：氨氧化细菌AOB-amoA基因丰度与PNR及地上净生物量显著正相关，且对地上净生物量具有显著的直接作用；反硝化功能基因nosZ基因丰度与反硝化酶活性显著正相关，其群落组成对地上净生物量具有显著且间接的负效应。综上所述，不同草原生态系统中，氨氧化细菌丰度对施氮处理的响应特性可以为评估土壤质量变化提供了指示作用；全球变化背景下，不同草原类型氮循环微生物功能对土壤环境因子的响应存在差异，暗示着氮循环微生物对全球变化响应具有一定的区域分异性。 |
| 英文摘要 | As the important ecological barrier of China, the grassland ecosystem played an irreplaceable role in water conservation, climate regulation and maintaining key nutrient cycles (carbon and nitrogen cycle) and energy flow. Due to global change (nitrogen deposition, precipitation regime and land use), net primary productivity (NPP) was significantly decreased, thereby influencing ecolobical structure and function. Considerable effects had been devoted to investigate the effects of changes in carbon and nitrogen of ecosystem on aboveground ecogocial processes, while the response mechanism of soil functional microbial groups involved in C and N cycling was still unclear. Researches on effects of global change on functional microbial groups mostly focused on single factor, single ecological process or single ecosystem, and ingonred the feedback of soil microbial groups between above- and below-ground ecosystems.Three field experiments were established in three types of grassland ecosystems in this study (typical grassland, desert grassland and alpine meadow) along a latitudinal gradient. Different ecosystems had different factors. The effects of N addition and mowing, water-table lowering and mowing on soil functional microbial groups were investigated in typical grassland and alpine meadow, respectively. Two experiments were established in desert grassland, one was the effect of different grazing intensities on soil microorganisms, and the other was the effect of N addition and precipitation regimes on soil microbial groups. We analyzed the response mechanisms of abundances, compositions and diversities of functional microbial groups involved in soil C and N cycling to global changes by using real-time PCR, T-RFLP and clone library technology. The research contents and main findings of this thesis were described as follows:(1) As for northern temperate grassland (typical grassland and desert grassland), N addition significantly decreased soil pH, soil nitrate concentration was significantly increased with N addition and precipitation enrichment. Mowing significantly decreased nitrate content and had no obvious influence on ammonia content, while grazing significantly increased ammonia content and had no strong effect on nitrate content. As for alpine meadow, both water-talbe lowering and mowing significantly decreased soil pH and soil respiration, and had an interactive effect on soil pH and nitrate content.(2) As for northern temperate grassland (typical grassland and desert grassland), N addition significantly increased AOB-amoA gene abundance. As for alpine meadow, both water-talbe lowering and mowing had no significant effect on functional groups abundances, while relative abundance of AOB-amoA gene responded sensitively to mowing. N addition significantly increased cbbL gene abundance function in CO2 fixation, and played an interactive effect on that with mowing in typical grassland. Changes in soil pH, nitrate content and water content played a key role in functional microbial community structures.(3) Ammonia oxidizers and denitrifiers played a key role in above- and below-ground ecosystems. Abundances of AOB-amoA and nosZ genes were the major factor on PNR and DEA, respectively. AOB-amoA gene abundance had a direct and positive influence in ANPP, while nosZ gene community structure negatively affected ANPPOverall, changes in abundance of AOB in response to N addition provide an indicator for evaluating soil environmental quality. Differences in responses of microbial functional groups involved in N cycle to environmental factors suggest that responses mechanisms of N-related functionalgroups to global change have regional characteristic. |
| 中文关键词 | 氮沉降 ; 割草 ; 放牧 ; 改变降水 ; 功能微生物 |
| 英文关键词 | N deposition mowing grazing precipitation regimes functional groups |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院生态环境研究中心 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288044 |
| 推荐引用方式 GB/T 7714 | 孙翼飞. 模拟全球变化对三种草原土壤碳氮循环微生物的影响[D]. 中国科学院大学,2018. |
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