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题名: 全球气候变化背景下高寒区土壤微生物的演变特征
作者: 曾军
学位类别: 博士
答辩日期: 2016-11
授予单位: 中国科学院研究生院
授予地点: 北京
导师: 贺纪正
关键词: 全球气候变化,高寒区,暖湿化,冰川退缩,土壤微生物,演变特征 ; Global climate change, alpine ecosystem, warming and wetting climate change, soil microbial community, successional pattern
其他题名: Successional patterns of soil microbial communities in the alpine ecosystems under the scenarios of global climate change
学位专业: 生态学
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。高寒区土壤是地球上最重要的碳库之一,土壤微生物的活性和群落组成又是控制土壤碳“汇”还是“源”的关键。因此,高寒区暖湿化气候变化背景下,土壤微生物时空演变特征的研究将会有助于我们预测气候变化对高寒区土壤微生物造成的可能影响以及微生物对气候变化的响应。基于此目的,本研究选择中国新疆天山1号冰川前缘土壤生态系统和西藏高寒草原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。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,来评估气候变化对局域和区域尺度下土壤微生物的影响及微生物对气候变化的响应。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功能基因)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碳源利用速率最高。
    (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,共采集到表层和亚表层土壤样品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。相关分析结果显示干旱度(1 - 年均降水量/年均潜在散蒸量),是土壤原核微生物群落组成变异最大影响因素。进一步对表层和亚表层土壤原核微生物沿干旱度分布特征进行分析发现,表层和亚表层土壤细菌和古菌群落组成呈现出按照干旱度增加的指向性演替规律。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。相关分析结果显示干旱度是不同类型草原土壤微生物群落变异的最大影响因子,而土壤养分是表层和亚表层微生物变异的最大影响因素。
(3)进一步的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0.10<干旱度<0.73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,可能的机制是通过抑制湿地草原土壤N2O还原细菌丰度进而促进N2O气体排放。
英文摘要:      Under the scenarios of global warming, the climate of alpine ecosystems in western China is mainly characterized by warming and wetting.Alpine glacier and the Qinghai-Tibetan plateau are among the most sensitive regions on Earth to global climate change. Alpine soil is one of the most important terrestrial organic carbon pools on Earth, while soil microbial community activity and compositions play important roles in soil carbon sink or source. Therefore, the study of temporal and spatial variation of microbial community may facilitate the prediction of the possible impacts of climate change on soil ecosystem and microbial feedbacks to climate changes. In this study, we selected two typical alpine 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) using molecular methods. We compared microbial successional patterns between the small and the larger sampling scales to estimate the influence of climate change on soil microbial communities at local and regional scales. The main research contents and results are listed as follows.
    (1) 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 were analyzed by using space substitute time method. Soils that deglaciated between 1959 and 2015 (including 10 soil samples) were collected. Soil bacterial and N-cycling community (including N-fixer, ammonia-oxidizers and denitrifiers) compositions are structured by substrate age: that is, soils could be assigned into initial (0-5 years), intermediate (8-34 years) and later stages (40-50 years). Soil microbial diversity showed an increasing trend and significant changes were 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 carbon and nitrogen were the primary factors 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.
    (2) At larger scale, 144 soil samples (including both surface and subsurface soils) were collected from 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 wetlands, alpine meadow and alpine steppes, respectively. Soil bacterial and archaeal compositions were analyzed using Illumina Miseq profiling of 16S rRNA gene. The results showed significant difference in microbial community structures between the three ecosystems. Redundancy analysis showed aridity (1-mean annual precipitation/mean annual potential evapotranspiration) is the most important factor influencing microbial community composition. Further ordination analysis showed that bacterial and archaeal community compositions in both soil horizons are presented in directional patterns along the aridity gradient. Correlation analysis showed prokaryotes in subsurface soils responded 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 with increasing aridity, but the decreasing rate was higher in subsurface soils than in surface soils. However, soil bacterial diversity in surface soils significantly increased as aridity increased, whereas it non-significantly decreased with increasing aridity in subsurface soils. Correlation analysis showed that aridity was the most influencing factor to variations of soil microbial communities in horizantoal distribution, but soil nutrients contributed to the variation of microbial communities in different soil layers.
    (3) Further N-cycling functional community composition, gene abundances (including ammonia-oxidizing bacteria and archaea, nirS, nirK and nosZ coding bacteria) and their mediated N turnover activities (including potential nitrification rate and denitrification enzyme activities), 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 0.10 < aridity < 0.73. Structural equation modeling analysis revealed that aridity had a strong direct negative effect on DEA, and indirectly impacted N cycling functional community gene abundances, community structure and diversity by strongly affecting soil pH, soil physical properties and other nutrients.
    In summary, soil microbial community compositions, diversity and functions showed similar successional patterns regardless of different sampling scales. At small scale, soil organic carbon and nitrogen are the main driving factors to microbial community composition. While at large scale, climate is the main influencing factor to archaeal horizontal and vertical variation; but environmental factors mainly contributed to the vertical variation of bacteria. Besides, the projected warming and wetting will have a strong impact on soil microbial communities in the alpine steppes, while the most significant N loss through N2O emission could mainly occur in mesic areas.
内容类型: 学位论文
URI标识: http://ir.rcees.ac.cn/handle/311016/36779
Appears in Collections:中澳联合土壤环境研究室_学位论文

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Recommended Citation:
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]. 北京. 中国科学院研究生院. 2016.
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