Knowledge Resource Center for Ecological Environment in Arid Area
| 我国北方典型自然生态系统AM真菌地理分布格局及驱动因子研究 | |
| 其他题名 | AM fungal biogeography in typical natural ecosystems in northern China |
| 徐天乐 | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 陈保冬 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 丛枝菌根真菌（AM真菌）是广泛存在于陆地生态系统中的共生微生物，能够与80%以上的陆生维管植物形成菌根共生体系。该类真菌完全依赖于植物获取生长所需的碳水化合物，作为回馈，能够对宿主植物的生长发育提供多方面的帮助，如：促进植物对磷、氮等养分元素的吸收、提高植物对干旱胁迫和病原菌的抵抗能力等。因此，AM真菌对于维持生态系统的功能以及可持续性具有重要意义。目前，在较大空间尺度下开展的有关AM真菌群落结构及其驱动因子的研究较为有限，特别是在区域尺度更是如此。已有研究发现AM真菌空间分布格局可能与多种生物和非生物因子相关，但并未得到较为一致的结论，且少有研究同时对这些因子的相对解释率进行评估。因此，为了更好的揭示AM真菌在生态系统中的作用及其对环境变化的响应，亟待开展较为系统、全面的AM真菌生物地理相关研究。本研究在我国北方由东至西布设了一条5000公里的调查样带，涵盖了多种典型自然植被类型，包括：灌丛、典型草原、草甸草原、荒漠草原及荒漠。综合运用变差分解、多元回归矩阵（Multiple regression on distance matrices）、基于非参数多元方差（PerMANOVA）等手段，对不同因子与AM真菌生物地理分布格局的关系进行了定量解构，并对不同植被类型及生态系统中的AM真菌群落结构进行了比较。论文的主要研究内容和结果如下：区域尺度下AM真菌地理分布格局驱动因子通过高通量测序手段（Illumina Miseq）确定了47个取样点的AM真菌群落结构，涉及四种植被类型，分别为典型草原、草甸草原、荒漠草原及荒漠。共检测到12个属的AM真菌，划分为137个OTU（可操作分类单元），其中54%的OTU属于Glomus属。研究结果表明，AM真菌物种丰富度和系统发育多样性均与土壤pH值呈显著负相关。不同种类的AM真菌的最适土壤pH值有所差异，pH值过高的土壤可能会导致一些AM菌种的消失。此外，土壤pH值也是多个对AM真菌群落具有影响的生物和非生物因子的综合表征，这也可能是pH值与AM真菌多样性密切相关的主要原因。尽管已有大量研究探讨了宿主植物对AM真菌群落结构的影响，但大部分是基于植物根部样本或仅涉及较少的植物种类。本研究在植物群落组成异质性较高的调查样带上对土壤样本进行采集（共涉及植物237种），证实了在区域尺度上植物群落组成对AM真菌的空间分布格局具有较强的预测能力，即：AM真菌群落组成的分异与植物群落组成密切相关。该结果可能与宿主植物更倾向于对自己更为有利的AM真菌类群提供光合产物有关。 本研究同样发现地理距离能够较大程度上解释AM真菌群落组成变化。由于AM真菌的孢子主要依靠风和动物进行传播，其空间分布格局可能与扩散限制作用相关。更为重要的是，地理距离是AM真菌系统发育格局的首要预测因子，表明历史进化和生态事件可能会对当代AM真菌的群落结构产生重要影响。非生物因子仅能有限解释AM真菌群落组成变化。以往大量在局域尺度或景观尺度的研究认为非生物因子是塑造AM真菌群落结构的关键因素。然而，不同调控因子对微生物群落特征的解释能力会随着尺度的改变而发生变化。本研究表明在较大空间尺度下，非生物因子对AM真菌生物地理格局的预测能力明显减弱。不同植被类型下，在考虑物种多度的情况下，AM真菌的群落组成具有显著差异。通过指示种分析，发掘了54个AM真菌可以作为特定植被的指示性物种，来自Diversispora 和Claroideoglomus两个属的一些AM真菌菌种分别具有指示荒漠草原和荒漠的潜力。2）灌丛生态系统和草地生态系统AM真菌群落结构及驱动因子比较灌木对草地生态系统的入侵在全球范围内广泛存在，特别是在干旱和和半干旱环境下更是如此。近年来由于全球气候变化的原因，这一现象的发生更为频繁。虽然大量研究探讨了草地生态系统演变为灌丛生态系统的机制和后果，但主要是针对地上生物群落，对于地下部分则关注较少，例如AM真菌便是如此。本研究在干旱和半干旱区域设置了16个样点对比了两种植被类型下AM真菌群落结构及它们各自的驱动因子。研究结果表明，两种生态系统AM真菌优势属均为Glomus，与草地生态系统相比，灌丛生态系统Acaulospora，Archaeospora和Scutellospora属的相对丰度较高（P < 0.05）， 而Funneliformis属则相反。草地和灌丛生态系统AM真菌的物种丰富度和组成均未表现出显著差异。土壤黏粒含量和C/N分别是灌丛和草地生态系统AM真菌多样性的关键驱动因子。两种生态系统中AM真菌群落组成均与植物群落组成显著相关。然而，灌丛生态系统AM真菌群落组成并未与草本层植物群落组成表现出显著的相关性，仅与灌木层的物种组成紧密联系，暗示弱菌根或非菌根植物的存在会对AM真菌的群落结构产生重要影响。此外，以往（近50年）气候变化的幅度（温度和降水）也是草地生态系统AM真菌群落组成的重要预测因子。 |
| 英文摘要 | Arbuscular mycorrhizal (AM) fungi are common and important symbionts in terrestrial ecosystems. AMF belong to the phylum Glomeromycota, represent obligate plant-root symbionts and associate with ~ 80% of terrestrial plant species. AMF are entirely dependent on their hosts for the supply of carbohydrates. In return they provide a range of benefits to host plants, including improved phosphorus and nitrogen acquisition, enhanced drought tolerance and pathogen resistance. Therefore, AM fungi play a key role in ecosystem functioning and sustainability. So far, studies on AM fungal biogeography are still limited, especially at regional scale. Prevous studies showed that several biotic and abiotic were related to AM fungi distribution patterns, but there is no consistent conclusion about AM fungi biogeographic patterns and their controlling factors, and few studies attempted to simultaneously quantify the relative contribution of each of theses factors. To further reveal the role of AMF in ecosystems and their response to environmental changes, comprehensive and systematic studies about AM fungi biogeograohy are urgently needed. In the present study, we investigated AMF communities across a transect spanning over 5000 km (maximum distance across sites) in northern China. The transect covered a wide range of vegetation types (meadow steppe, typical steppe, desert steppe, desert and shrubland) We explored the relative importance of different factors in predicting AMF biogeographic patterns, and compared AM fungi communities in different vegetation types or ecosystems, by using multivariate statistics, such as Multiple regression on distance matrices, PerMANOVA and variation partition.The main findings of the study are as follows:The key drivers of AM fungi spatial distribution pattern at reigenal scaleWe determined the AM fungi community structure at 47 sampling site in typical steppe, meadow steppe, desert steppe and desert using Illumina sequencing. . A total of 137 AM fungi OTUs were identified, which covered 11 AM fungi genera. Among them, the OTUs belonging to Glomales were the overwhelming majority (54%).We found that soil pH correlated negatively with AMF richness and phylogenetic diversity. AM fungi species differ considerably in their optimal pH ranges, and it was possible that some AMF species would disappear from these extreme alkaline soils. Moreover, the soil pH may represent a general index for a number of abiotic or biotic factors in determining AMF richness in the grasslands in northern China, which may drive different fungal community characteristics across the sampling sitesSome recent studies have explored the role of host plants in shaping the AMF community at large spatial scale. However, most of these studies were based on root samples, limited by the relatively small numbers of plant taxa included or only considered the role of plant biomass. Here, across the transect with high heterogeneity in plant community (including 237 plant species in total), we show that the plant community composition was a strong predictor for soil AM fungi distribution at the regional scale. This suggests that plots with divergent plant communities harbor distinct soil AM fungi communities. One explanation may be that host plants exhibited preferential allocation of photosynthates to more beneficial AM fungi partners.In our study, we found that a large fraction of explained variance of AM fungi community composition could be attributed to geographic distance. AM fungi have been reported to be mainly dispersed by wind or animals, and thus dispersal constraints may contribute to AM fungi biogeography. Our study showed that the AM fungi phylogenetic patterns could be predominantly explained by geographic distance, which implies that past evolutionary and ecological events may play a role in shaping the current assemblages of AM fungi communities.The abiotic factors only explained a small fraction of the variation in AM fungi biogeographic patterns. Some studies conducted at local or landscape scales have shown that abiotic factors are the key driver in shaping AMF community composition. However, because the relative importance of different regulating factors of microbial communities may change across different spatial scales, our study highlights that the relative importance of the abiotic factors in determining AMF distribution patterns weakens at large spatial scales. Vegatation types were more likely to influence the relative abundance of AM fungi taxa but not the absence/presence of those. Through indicator species analysis, 54 OTUs were chosen as indicator species for vegetation types. In our study, some taxa belonging to Diversispora and Claroideoglomus may have the potential to indicate desert steppe and desert respectively.AM community structure and the driving factors in grassland and shrubland ecosystems.The woody plant expansion in grassland is occurring worldwide. In arid and semiarid ecosystems, which are vulnerable to extreme climatic regimes, the conversions of grassland to shrubland via ecological state transitions are especially common. Compared with above-ground organisms, little is known about the effects of theses transitions on soil microbes. This is the case with arbuscular mycorrhizal (AM) fungi. Here, we present a field study spanning over 16 arid or semiarid ecosystem sites in northern China, to compare the distribution patterns and driving factors of soil AM fungi communities in shrubland and grasslandIn both grassland and shrubland, the majority of the AM fungal OTUs and sequence reads belonged to Glomus. The relative abundances of Acaulospora, Archaeospora and Scutellospora were significantly higher in shrubland than those in grassland, whereas Funneliformis was the opposite. No significant differences were observed in both AM fungal community richness and composition between grassland and shrubland. Pearson correlation showed that AM fungal richness was significant correlated with C/N in grassland, while with clay in shrubland. AM fungi community composition was significantly predicted by plant community composition in both grassland and shrubland, but only showed significant association with shrub community composition in shrubland, which implies the occurrence of no/poor AM fungi plant may affect the spatial distribution of AM fungi. Moreover, in grassland, AM community compostion was also significantly related to the the variability of climatic factors (annual temperature and annual precipitation) in the past 50 yr. |
| 中文关键词 | AM真菌 ; 生物地理 ; 植物群落 ; 地理距离 ; 非生物因子 |
| 英文关键词 | AM fungi biogeography plant community geographic distance abiotic factor |
| 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/2XILL650/287913 |
| 推荐引用方式 GB/T 7714 | 徐天乐. 我国北方典型自然生态系统AM真菌地理分布格局及驱动因子研究[D]. 中国科学院大学,2017. |
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