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贡嘎山海螺沟冰川退缩区植被演替的地下驱动机制

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2024-11-02 08:35

QQWeiboFeedback 贡嘎山海螺沟冰川退缩区植被演替的地下驱动机制 Alternative TitleElucidating plant community succession and belowground driving forces in Hailuogou Glacier Chronosequence Language中文姜永雷 Thesis Advisor李春阳 ; 张胜 2019-07-01 Degree Grantor 中国科学院大学 Place of Conferral成都 Degree Discipline生态学 Keyword海螺沟冰川退宿迹地植被原生演替稀有细菌随机和确定过程胞外酶活性 Abstract贡嘎山海螺沟冰川经过近120年的退缩演化，在长约2000 m，宽50-200 m，海拔范围2850-3000 m(垂直高差仅150 m)之间演化出完整的可以定龄的土壤序列和从先锋群落到顶级群落的连续植被原生演替序列。然而对于早期生态系统发育过程中植被演替的驱动机制还不太清楚。鉴于此，本研究以海螺沟冰川退缩迹地不同演替阶段植物、土壤和土壤微生物为研究对象，探讨海螺沟冰川退缩迹地植被演替的驱动机制。通过对不同演替阶段地上植物类群变化、养分(N、P等)利用策略与植物(细根、叶)生态化学计量关系的变化，探讨演替过程中，地上植被群落聚集模式和驱动群落变化的内在机理。此外，通过不同演替阶段地下土壤微生物结构和功能特征变化的研究，探索演替过程中土壤-微生物的耦合关系与协同效应。主要研究结果如下：(1) 通过对不同演替阶段植物群落取权重，我们量化了11种元素在植物群落叶和细根中分配和调控模式、氮磷生态化学计量变化以及生物和非生物因子在植物演替中的驱动作用。随着演替的进行，植物群落叶片累积较高浓度的大量元素(例如，N、P、Mg和K)和具有较低的变异系数；而群落细根中包含较多的微量元素(Al、Fe和Cu)且具有较高的变异系数。从演替的早期到晚期阶段，群落叶片N:P显著增加(变化范围8.2-20.1)，推测植物生长的限制因子由早期的N向后期的P转变。在演替早期阶段，土壤因素(包括pH值、土壤容重与土壤氮含量)对演替早期群落特征聚集起着确定性过滤作用；而生物因素(种群丰富度和凋落物生物量)对演替后期群落竞争排斥的解释能力增加。(2) 通过对海螺沟冰川退缩迹地中土壤微生物群落结构、土壤微生物胞外酶活性和球囊霉素相关蛋白(GRSP)进行研究，我们探讨了植被演替过程中地下土壤微生物的营养限制机制，解耦合土壤和生物因素的影响。随着土壤龄级的增加，微生物生物量显着增加，在演替后期达到最大值。另外，演替前期微生物群落呈现明显的细菌为主而演替后期转变为真菌主导的变化趋势。在胞外酶化学计量学和阈值元素比率分析的基础上，我们发现微生物资源限制在不同的土壤发育阶段有显著差异。在演替的早期阶段，微生物更加受土壤碳和氮限制，而在演替后期，可能由于磷酸盐的快速流失微生物磷限制现象变得更加严重。此外，冗余分析和结构方程模型分析表明，土壤因子是影响微生物过程的主要因素，特别是在早期阶段；而在演替后期随着森林覆盖重要性的增加，生物因子的解释能力在演替的晚期阶段显著增加。(3) 从土壤微生物的角度，通过高通量测序研究了土壤细菌和真菌群落对地上植被群落演替和土壤发育状态的响应，分析其在海螺沟冰川退缩迹地的组成和演替动态。探讨下行效应控制土壤养分和植被改变的相对贡献以及来自线虫食草动物的上行效应压力。结果表明，在营养贫瘠的早期阶段，一些耐贫瘠的细菌(例如，土杆菌属，单胞菌属和硫杆菌属等占据优势。在演替的中期，由于环境压力较小，不同的生物生态位选择性广泛，导致微生物种类和多样性较高。在演替的晚期，一些与植物根系相关的外生菌根真菌增多(例如，透孢黑团壳属，红菇属，蜡壳菌属以及一些能够分解复杂有机物的细菌(例如，苯基杆菌属，慢生根瘤菌属，伯克氏菌属和丰佑菌属增多。此外，细菌和真菌群落的共发生网络和指示物种分析表明其结构复杂程度均在演替的中期达到最大，细菌主要的菌门为变形菌门和酸杆菌门；而真菌主要菌门为子囊菌门和担子菌门。方差分解和结构方程模型分析表明：在演替的早期，土壤性质是影响微生物群落构成的主要因素。而在演替的后期随着森林覆盖的增加，生物因子(植物丰富度、线虫)的对细菌和真菌群落结构变化的解释能力的重要性增加。此外，细菌群落在组装过程中显示出更紧凑的网络拓扑结构，表明确定性过程的重要性，而真菌群落中比较松散的聚类表明其结构更多地受随机过程的影响。由上可知，在贡嘎山冰川退缩区，土壤微生物在驱动植被原生演替过程中起着关键作用。(4) 基于前期的高通量数据，更深层次的探究演替序列中稀有和丰富的细菌子群落的空间周转，生态多样性以及共发生模式和分布模式。结果表明，细菌群落(总的细菌、丰富和稀有细菌子群落)显著的聚集为3个集群。稀有细菌子群落分布可能受随机过程的限制(周转)，而丰富细菌子群落主要受确定性过程驱动(土壤因子)。通过共发生网络分析，稀有和丰富的细菌子群落结构在演替的中间阶段比早期和晚期更复杂。而且，丰富的微生物群落在网络结构中占据核心位置，与其他微生物类群子群落关系密切，而稀有类群则没有。然而，与丰富的细菌子群落相比，稀有细菌子群落表现出更高的多样性和更强的空间周转。方差分解表明生物和土壤因子的相互作用是丰富和稀有微生物构建的主要驱动力，但它对稀有细菌子群落的解释能力(19.43%)远低于丰富细菌子群落。此外，冗余分析和结构方程模型表明，丰富和稀有细菌子群落受到不同环境因子的影响。与演替的早期和晚期相比，中期阶段具有较低的环境压力和更广泛的生态位，导致更复杂的微生物网络结构。而且，丰富细菌在微生物网络结构中位于核心位置。由此可知，微生物-微生物相互关系在驱动海螺沟冰川退缩迹地植被原生演替过程中扮演了不同的角色。探索演替过程中丰富和稀有微生物群落的结构和潜在功能，能更加深层次的解译植被原生演替过程地下驱动的关键机理。综上所述，本研究借助生态化学计量和分子生物学方法，以海螺沟冰川退缩迹地不同演替阶段的植被-土壤为研究对象，分别从植物、土壤和微生物的角度研究了不同演替阶段下土壤营养状态，植物和微生物的聚集模式和驱动机制，以期揭示原生演替过程中，植被群落演替的地下驱动机制以及植被-土壤-微生物的耦合关系和协同效应。研究结果能为认识高山植物种间相互作用、植物-微生物群落的构建机制以及环境变化下地上-地下生物组成和演替动态提供科学依据，实践中也为退化山地植被恢复与管理提供技术指导。 Other AbstractThe Hailuogou glacial retreat is observed during the past 120 years, which leaves behind a primary succession along soil chronosequences. Along the approximately 2 km-long belt, width (50-200 m), elevation (from 2850 to 3000 m), a series of sites representing different stages of vegetation succession can be readily recognized, from a barren stage with some mosses to a climax and lush forest stage. Thus, the glacier provides an excellent place to study the relationship between vegetation succession and soil development. However, it is not clear about the plant-soil-microbiota interactions and driving factors of successional dynamics in glacier retreat areas. In this study, through the changes of the plant community, nutrient (N, P, etc.) utilization strategies and the ecological stoichiometry, we investigated the patterns and mechanisms for plant community assembly across the chronosequence, and the underlying environmental and biological driving forces. Moreover, both microbial structure and functional characteristics associated with different stages of soil development were studied to disentangle the coupling and synergetic stimulation of plant-soil-microbiota trajectories. The main results and conclutions were follows:(1) Through community-weighted approaches, we quantified elements allocation and regulation in leaves and roots, N:P stoichiometry, and the biotic and abiotic controls guiding community dynamics along the 120-year chronosequence. Across seven primary successional stages, plant leaves featured higher concentrations of macro-elements with lower coefficients of variation (CV) with increasing succession; whereas, fine roots contained more micro-elements with higher CV. From the early to late stages, foliar N:P increased linearly from 8.2 to 20.1. These findings highlighted that the limiting factor for plant growth shifted from N to P over one century of deglaciation. Edaphic factors (pH, bulk density, N and P concentrations) acted as deterministic filtering for trait convergence in the early stages, while biotic factors (species richness and plant litter biomass) for competitive exclusion dominated the late stages hosting species with stronger homoeostatic regulation and more conservative nutrient use.(2) In this study, we investigated changes in the microbial community structure, ecoenzymtic stoichiometry, and glomalin-related soil protein (GRSP) accumulation in the Hailuogou Glacier Chronosequence, located in the eastern Tibetan Plateau. We wanted to reveal the effects of nutrient limitation on soil microbes and the relative contributions of edaphic and biotic factors. The results showed that with an increasing soil age, there was a steady increase in the microbial biomass and a shift from a bacterial to fungal dominated pattern. Soil enzyme stoichiometry and analyses on threshold elemental ratios revealed that microbial activities were limited by carbon and nitrogen during the early successional stage (3-52 years), while phosphorus was the main limiting factor during later stages (80-120 years). Moreover, the redundancy analysis and structural equation modeling suggested that during early stages edaphic factors had a greater impact on microbial processes, while the vegetation factors were most influential during the last two stages. Overall, these results highlighted the importance of integrating knowledge of the microbial community structure, soil enzyme activities and GRSP to gain a holistic view of soil-plant-microbe interactions during ecosystem successions. (3) In this study, we analyzed both bacterial and fungal lineages associated with seven di?erent stages in the Hailuogou Glacier Chronosequence, to quantify their taxonomic composition and successional dynamics, and to decipher the relative contribution from the bottom-up control of soil nutrients and altered vegetation as well as top-down pressures from nematode grazers. Moreover, some versatile bacteria (e.g. Geobacter, Polaromonas and Polaromonas), including phototrophs, chemoautotrophs and chemoheterotrophs, characterized the two early oligotrophic stages. At the middle stages, a lower level of environmental stresses and a wider selection of different niches resulted in the highest richness and diversity of microbial OTUs. The last two stages involved a proliferation of root-associated ectomycorrhizal fungi (e.g. Massarina, Sebacina and Archaeorhizomycetes) and bacterial taxa capable of degrading complex organic compounds (e.g. Phenylobacterium, Granulicella, Granulicella and Opitutus). Besides, co-occurrence networks showed that the community complexity for both bacteria and fungi typically peaked at the middle chronosequence stages. The overlapping nodes mainly belonged to Proteobacteria and Acidobacteria in bacteria, and Ascomycota and Basidiomycota in fungi, which was further supported by the indicator species analysis. Variation in partitioning and structural equation modeling suggested that edaphic properties were the primary agents shaping microbial community structures, especially at the early stages. The importance of biotic factors, including plant richness and nematode feeding, increased during the last two stages along with the establishment of a coniferous forest, eventually governing the turnover of fungal communities. Moreover, bacterial communities exhibited a more compact network topology during assembly, thus supporting determinism, whereas the looser clustering of fungal communities illustrated that they were determined more by stochastic processes. These pieces of evidence collectively reveal divergent successional trajectories and driving forces for soil bacterial and fungal communities along a glacier fore?eld chronosequence.(4) We used Illumina sequencing datasets to investigate temporal dynamics, ecological diversity, and the co-occurrence patterns of abundant and rare bacteria associated with different stages of soil development in the Hailuogou Glacier Chronosequence. Our results showed that bacterial assemblages (all, abundant and rare bacterial communities) are strikingly separated into three distinct clusters along the seven stages of the 120-year old soil chronosequence. The assemblages, except for the rare taxa, signi?cantly differentiated with an increasing soil age. However, rare taxa exhibited higher diversities and stronger temporal turnover when compared to abundant taxa. Variation partitioning showed that the interactions of biotic and edaphic factors were the main driving forces in shaping both the abundant and rare microbial structures, but it had a much lower explaining capacity for rare taxa (19.43%) than for abundant taxa. Furthermore, the redundancy analysis and structural equation models showed that abundant and rare subcommunities were influenced by distinct environmental factors. Compared to the early and late stages, the middle stages causing lower environmental stress and a wider diversity of niches resulted in more complex microbial networks. Furthermore, the microbial network analysis revealed that abundant taxa are positioned in central locations, which might be irreplaceable for network persistence.In conclusion, through comprehensive ecological stoichiometry and molecular biology methods, we can explore the patterns and mechanisms for plant and microbial community assembly in different vegetation succession and soil development. Based on these researches, we will disentangle the coupling and synergetic stimulation of plant-soil-microbiota trajectories. Our research has implications for integrated studies on biogeochemical impacts of vegetation changes and nutrient status development. Further, our results will contribute to improved predictions of the direction and intensity of primary succession, and also to improved management practices related to nutrient limitation during long-term soil development. Pages160 Document Type学位论文 Identifierhttp://ir.imde.ac.cn/handle/131551/33978 Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714 姜永雷. 贡嘎山海螺沟冰川退缩区植被演替的地下驱动机制[D]. 成都. 中国科学院大学,2019. Files in This Item: File Name/Size DocType Version Access License 201518006310004.pdf（9108KB）学位论文开放获取CC BY-NC-SAView Related ServicesRecommend this itemBookmarkUsage statisticsExport to EndnoteGoogle ScholarSimilar articles in Google Scholar[姜永雷]'s ArticlesBaidu academicSimilar articles in Baidu academic[姜永雷]'s ArticlesBing ScholarSimilar articles in Bing Scholar[姜永雷]'s ArticlesTerms of UseNo data!Social Bookmark/Share File name: 201518006310004.pdf Format: Adobe PDF

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