Knowledge Resource Center for Ecological Environment in Arid Area
| 全球气候变化背景下高寒区土壤微生物的演变特征 | |
| 其他题名 | Successional patterns of soil microbial communities in the alpine ecosystems under the background of global climate change |
| 曾军 | |
| 出版年 | 2017 |
| 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 | 全球气候变暖背景下，中国高寒区生态系统正经历着以升温和增加降水为主要特征的暖湿化气候变化趋势。高山冰川和青藏高原等高海拔地区是高寒生态系统中对气候变化最敏感的区域。冰川不同时间退缩暴露出的土壤呈现出一条天然的土壤发育演变的时间序列，是研究土壤发育过程中一些重要生物地球化学过程演变的理想材料。通过对比近期和往期暴露土壤的特性能够揭示气候变化过去、现在和未来对土壤发育过程的影响。土壤微生物作为土壤发育过程中不可或缺的组成部分，随着土壤发育演变其群落组成、多样性、活性以及功能将会呈现出一定的演变特征。因而透过土壤微生物的演变特征能够反演和预测气候变化对土壤生态系统过程将会造成的影响。另外，通过对小尺度（米）和大尺度（千米）采样下微生物群落演替特征的比较，能够对气候暖湿化对高寒区土壤微生物的影响进行较全面的评估。基于此目的，本研究选择高寒生态系统中两种对气候变化较敏感的生态系统，即中国新疆天山1号冰川前缘土壤生态系统和西藏高寒草甸土壤生态系统为对象，采用分子生物学方法研究了土壤原核微生物群落组成、多样性和功能活性沿自然梯度（如时间序列，降水温度梯度）的演变特征，主要研究内容和结果如下。（1）在小尺度水平上，以地理距离代替时间，采集了天山1号冰川前缘不同暴露时间点的土壤样本，分析了土壤原核微生物群落组成、土壤酶活性和碳源利用特征。结果显示细菌和氮循环功能微生物群落组成（包括固氮，氨氧化和反硝化过程涉及的原核微生物基因）随冰川退缩距离增加而呈现出明显的演替规律，即冰川前缘土壤按照暴露时间划分为早期（0-4年）、中期（8-34年）以及较晚期（40-50年）。土壤微生物多样性总体呈现出随演替时间增加而增加的趋势，但显著增加只发生在早期土壤向中期土壤过渡阶段，而在中期和晚期呈现出相对稳定状态。土壤酶活性总体呈现出随演替时间增加而增加，但在中期和较晚期土壤中呈现出一种相对稳定状态。相关分析显示，土壤碳和氮含量是细菌群落组成和氮循环功能微生物群落组成以及土壤酶活性沿时间序列变异的主要影响因素。进一步对不同碳源利用类型进行研究发现，早期土壤中微生物对氨基酸类碳源利用速率最高，而中期和后期土壤中则对碳水化合物类和多聚体类碳源利用速率最高。判别分析结果同样显示早期土壤与中期和较晚期土壤能够明显地区分开来。（2）在大尺度水平上，沿青藏高原从东向西的温度和降水梯度，设立24个采样点，历经全长1095 km，跨越2个纬度，10个经度，共采集到上亚表层土壤样品144份。青藏高原从东向西对应的地表生态类型为高寒湿地草原，高寒草甸和高寒荒漠草原。使用Illumina Miseq高通量测序方法分析了这三种不同生态类型土壤中细菌和古菌的群落组成。结果表明，土壤细菌和古菌在这三种生态类型中差异极显著。因子分析结果显示干旱度（1-年均降水量/年均潜在散蒸量），是青藏高原从东到西，土壤原核微生物群落组成变异的最大影响因素。进一步对上亚表层土壤原核微生物沿干旱度分布特征进行分析发现，上亚表层土壤细菌和古菌群落组成呈现出以干旱度为方向的指向性演替规律，并且亚表层土壤微生物对干旱度的响应似乎比表层土壤微生物更敏感，尤其是古菌比细菌响应更敏感。亚表层土壤中无论是细菌还是古菌其相对丰度与干旱度相关性均大于表层土壤。其中亚表层土壤中古菌对干旱度的响应速率明显大于表层。表\\亚表层土壤中古菌整体多样性指数差异极显著，并且随着干旱度增加古菌多样性呈现显著降低趋势（p<0.001），亚表层土壤降低速率明显高于表层土壤。多因子分析结果显示气候因子是土壤微生物群落变异的最大影响因子，而土壤养分是上亚表层微生物变异的最大影响因素。（3）将硝化和反硝化过程所涉及的氮循环功能基因丰度、群落组成和N转化酶活性进行整合，构建结构方程模型来解释和预测暖湿化气候变化对青藏高原草原生态系统氮循环过程的影响。结果表明，硝化过程和反硝化过程功能基因丰度，群落组成，多样性和氮转化活性与干旱度呈现出以干旱度=0.73为拐点的驼峰状或倒驼峰状二项式相关性。绝大多数微生物指标在干旱度>0. 73区域变化速率高于在0.73<干旱度<0.90区域。干旱度对反硝化酶活性具有直接的负相关作用，它通过直接影响土壤营养元素、质地来间接影响氮循环功能微生物群落组成和多样性。 综合以上研究结果表明：全球气候变化背景下，高寒区土壤微生物群落在不同尺度上呈现出相同的指向性演变特征。小尺度水平，土壤碳氮含量是冰川前缘土壤微生物群落演替的主要驱动因素。而在大尺度水平，气候是影响土壤古菌水平和垂直（剖面）分布主要因素，而土壤碳氮含量是土壤细菌垂直分布最大影响因素。青藏高原暖湿化气候变化将可能加速荒漠草原地区土壤微生物群落组成演变，通过抑制沼泽草原地区土壤N2O还原细菌群落组成和丰度进而促进N2O气体排放。 |
| 英文摘要 | Under the background of global warming, the climate of high cold ecosystems in western China is undergoing warming and wetting as the main characteristics of significant change. Alpine glacier and higher elevations of the Qinghai-Tibetan plateau are among the most sensitive regions on Earth to global climate change. As climate warms, terrestrial habitats that exposed after glacial retreat at different periods are considered as a natural succession chronosequence, which are the ideal environments for the investigation of key biogeochemical analysis by space substitute time. Through comparison of newly and past exposed soils, we could reveal and evaluate the impact of climate change on soil development in the past, present and future. Soil microbial communities are one of the indispensable parts of soil development. Their community structure, diversity, activity may exhibit in some successional traits during the process of soil development. Hence, we could deduct the impact of climate change on soil underground ecosystem through microbial community successional pattern. To the end, in this study we selected two typical alpine cold ecosystems, including Tianshan Mountain No.1 glacier forefiled soils and soils from grassland ecosystems of the Qinghai-Tibetan plateau, to investigate the successional patterns of soil prokaryotes along nature gradients (such as chronosequence, temperature and precipitation gradient) at different sampling scales by molecular methods. The main research contents and results are listed as follows.(1) In small scale, we investigated the primary successions of soil prokaryote composition, soil enzyme activity and carbon source utilization characteristics of heterotrophic microbial communities at the forefields of the Tianshan Mountains No. 1 Glacier by using space substitute time. Soils deglaciated between 1959 and 2015 (including 10 soil samples) were collected. Soil bacterial and N-cycling communities (including N-fixer, ammonia-oxidizers and denitrifiers) are structured by substrate age, that is the shift in community composition followed a directional pattern as it is characteristic for successional series. The different successional stages and dates could be separated into initial (0-5 years), intermediate (8-34 years) and later stages (40-50 years). Soil microbial diversity is presented an increasing trend and significant changes observed at the transfer from young to intermediate stages, while older soils appeared to have reached a temporary steady state. Correlation analysis revealed that soil organic carbon, was the primary factor influencing soil microbial community structure, diversity and soil enzyme activity. Further carbon-source utilization results showed amino-acid utilization rates were relatively higher in early soils, but carbohydrate utilization was higher in later stages. Discriminant analysis also revealed that newly exposed soils and older soils were well-separated from each other and obviously different from the reference soil.(2) In larger scale, 144 soil samples (including both surface and subsurface soils) were collected at 24 different sites along a strong temperature and precipitation gradient from west to east of the Tibetan plateau. The gradient is 1095 km in length and spans 2 latitudes and 10 longitudes. The gradient corresponding ground ecosystem types are alpine swamp meadow, alpine meadow and alpine steppes, respectively. Soil bacterial and archaeal compositions were analyzed by using Illumina Miseq profiling of 16S ribosomal gene (16S rRNA gene). The results showed significant difference in microbial community structures were observed between the three ecosystems. Factor analysis showed aridity (1-mean annual precipitation/mean annual potential evapotranspiration) is the most influencing factor to microbial community variation. Further ordination analysis showed bacterial and archaeal community structures in both soil horizons also followed a directional pattern as it is characteristic for aridity gradients. Correlation analysis showed prokaryotes in subsurface soils respond more sensitively than surface soils to aridity, and archaeal communities are more sensitive to changes in aridity than bacteria in alpine grassland ecosystem. The diversity of archaea was significantly reduced as aridity increased, but the reducing rate was higher in subsurface soils than in surface soils. While, soil bacterial diversity in surface soils was significantly increased as aridity increased, whereas it non-significantly decreased with increasing aridity in subsurface soils. Multi-factor analysis showed climate factors are the most influencing factor to soil microbial communities, but soil nutrients contributed to the variation of microbial communities in different soil layers. (3) Further N-cycling functional communities and their mediated N turnover activities, the abundance of ammonia-oxidizers (AOA and AOB) and denitrifers (NirK/S and NosZ genes containing communities) as well as N turnover enzyme activities (potential nitrification rate and denitrification enzyme activity (DEA)) of the samples were assessed. We found quadratic polynomial relationships between the aridity and soil microbial parameters (gene abundance, community structures, microbial diversity, and N turnover enzyme activity) with a threshold at aridity= 0.73. Soil microbial parameters were showed higher changing rate (linear increase or decrease) in areas with aridity>0.73 (alpine steppes) than in mesic areas with 0.73 |
| 中文关键词 | 全球气候变化 ; 高寒区 ; 暖湿化 ; 冰川退缩 ; 土壤微生物 |
| 英文关键词 | Global climate change high cold ecosystem warming and wetting climate change soil microbial community |
| 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/2XILL650/287838 |
| 推荐引用方式 GB/T 7714 | 曾军. 全球气候变化背景下高寒区土壤微生物的演变特征[D]. 中国科学院大学,2017. |
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