我国北方农牧交错带AM真菌多样性及其驱动因子研究
文献类型：学位论文
| 作者 | 向丹 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 陈保冬 |
| 关键词 | 北方农牧交错带 土地利用方式 菌根真菌 生物多样性 驱动因子 454高通量测序 |
| 其他题名 | Biodiversity of AM fungi in the farming-pastoral ecotone of northern China and the driving factors |
| 学位专业 | 生态学 |
| 中文摘要 | 在我国北方农牧交错生态脆弱区，由于自然环境变化和人类过度开发利用自然资源而导致生态环境恶化，生物多样性和土地生产力急剧下降。研究该区域生物多样性变化及其驱动因子，对于保护和合理利用本地生物资源，实现脆弱生态系统生态重建具有重要意义。基于AM真菌在生态系统结构和功能稳定中的关键作用，本研究运用分子生态学和生物地理学的理论和方法研究农牧交错带中关键土壤功能微生物丛枝菌根（AM）真菌的生物多样性，综合比较不同土地利用方式下AM真菌群落组成和多样性变化；通过多元分析和结构方程模型等定量解析环境因子对AM真菌生物多样性变化的相对作用大小，确定多样性变化的主控因子。论文 的主要研究内容与成果如下： 1）农牧交错带草地生态系统中AM真菌多样性、群落结构及其驱动因子 AM真菌在自然生态系统中的分布会受到各种环境因子的影响，但是因为传统研究方法，及研究区域的限制，其大区域尺度的分布规律及影响因子仍然不明确。本研究以我国北方农牧交错带为研究区域，综合考虑土壤、气候、植物、空间距离等可能对AM真菌产生影响的环境因子，并通过多元分析定量解析其相对作用大小，以揭示农牧交错带自然生态系统中AM真菌的分布规律及驱动因子。 研究结果表明，土壤结构及温度是影响北方农牧交错带草地生态系统中 AM真菌的主要环境因子，其中土壤结构是 AM真菌物种多样性的主驱动因子。AM真菌多样性与土壤粘粒、粉粒含量呈显著正相关关系，而与土壤沙粒含量呈显著负相关，说明该区域严重的土壤沙化已经成为影响 AM真菌多样性的重要因素。年均降水和土壤养分含量是植物多样性的重要驱动因子，但植物多样性与 AM真菌物种多样性之间没有相关性。 AM真菌群落结构的变化主要受到土壤因子的驱动，同时植物群落结构对AM真菌群落结构也产生显著影响，但空间地理距离及气候因子对 AM真菌群落的变化没有影响。在所有土壤因子中，土壤粉粒含量是 AM真菌群落结构的主驱动因子。植物群落结构对 AM真菌群落多样性的影响受制于土壤因子的作用。AM真菌的系统发育多样性同群落结构一样，主要受到土壤因子的驱动。与 AM真菌物种群落结构不同的是，AM真菌系统发育 Beta多样性没有受到植物群落的影响。在我们所考虑的所有土壤因子中，土壤有效磷是决定 AM真菌系统发育多样性的主驱动因子，其有效磷含量对系统发育 Beta多样性的影响为正向选择作用，即土壤中有效磷含量越高，AM真菌系统发育多样性越高。同样，空间距离阻隔对 AM真菌系统发育多样性没有产生影响。 2）土地利用方式对菌根真菌多样性的影响 草地开垦为农田是我国北方农牧交错带土壤退化的一个重要原因。草地变为农田会明显改变地上部植物群落和土壤理化性质，但对土壤功能微生物类群的影响目前还少见研究报道。我们第一次在区域尺度上比较研究了农田和草地两种不同土地利用方式对AM真菌多样性的影响，我们在农牧交错带选取50个样点，每个样点采取农田和草地的成对数据，通过454高通量测序方法检测土壤中AM真菌的物种组成，并结合环境因子探讨农田和草地间AM真菌物种多样性，丰度及群落结构差异，并探明其主驱动因子。 在北方农牧交错带总共发现 11个属101个OTU的AM真菌，农田和草地的优势属存在着明显差异。农田中 Glomus和Septoglomus为优势属，它们在农田中的相对丰度分别为 35.60%和23.61%。而在草地中只有 Glomus为优势属(69.13%)。Glomus属在草地中的比例显著高于农田，而Funneliformis、Septoglomus和Claroideoglomus这3个属在农田中的相对丰度显著高于草地。这是首次基于AM真菌新的分类系统，在区域尺度下明确证明农田和草地间属水平上的差异。在OTU的水平发现19个敏感型AM真菌OTU在草地中显著高于农田，11个抗干扰型AM真菌OTU在农田中显著高于草地。这为以后应用 AM真菌进行草地生态恢复或提高农田生产力提供了有价值的信息。 在北方农牧交错带草地开垦为农田显著降低了AM真菌的多样性、菌丝密度，并且明显改变了AM真菌群落结构。土地利用方式改变主要是通过提高土壤有效磷含量及改变土壤结构间接影响AM真菌多样性、菌丝密度及群落结构，直接干扰作用（如耕作等土壤扰动）则没有明显影响。在所有的因子中，土壤有效磷是驱动农田草地间AM真菌物中多样性和菌丝密度产生差异的主驱动因子。而土壤结构是影响AM真菌群落分布的主因子。 |
| 英文摘要 | In the farming-pastoral ecotone of northern China, biodiversity and land productivity have been decreasing dramatically due to environmental changes and over-exploitation of natural resources. For protection and sustainable utilization of local bio-resources, and also for ecological restoration of the degraded ecosystems,it’s urgent to reveal the regional biodiversity and uncover the driving factors. Based on the key roles of soil communities in stabilization of ecosystem structure and function, in the present study we investigated the diversity of arbuscular mycorrhizal fungi (AMF), a representative of functional soil microbial communities, in the ecotone, by means of molecular ecology and biogeography. The variation in AMF diversity under different land use practices has been described. Meanwhile, by multivariate statistics, such as Mantel and partial Mantel test and Structure Equation Modeling (SEM), relative importance of different environmental factors in the changes of AMF diversity, and the controlling predictors, has been revealed. The main findings of the study are as follows: 1）AM fungal diversity and their driving factors in grassland ecosystem. At present, the knowledge of AMF distribution pattern at regional scale is still quite limited. Several factors have been identified that may influence AMF distribution pattern, but to date most studies have been restricted to local geographical scales, or to a single soil type, and typically only communities inside plant roots have been analyzed. Conversely, few studies have simultaneously examined the effects of muliple environmental factors on AM fungal occurance. Therefore, it is not yet known how these AMF communities assembled in natural ecosystem. Here, we investigate AMF distribution at the regional scale in the farming-pastoral ecotone of northern China by using 454 pyrosequencing method. Meanwhile, by multivariate statistics, we quantified the relative importance of the potential driving forces including biotic and abiotic factors for AMF community. The results showed that soil structure and annual temperature were major predictors of AMF diversity (richness), and soil structure was the most prominant predictor. More specifically, AMF diversity was positively correlated with soil clay and silt content, but negatively correlated with soil sand content, suggesting that soil desertification has become the main reason of AMF richness loss in this fragile area. Average annual precipitation and soil nutrient content were important driving factors of plant diversity, but there was no correlation between plant and AMF diversity. AMF community composition was strongly influenced by soil properties and plant community, but not by geographical distance or climatic factors. Among all soil factors, soil silt content was the most important predictor for AMF community. By using partial Mantel test, we found no effect of plant community on AMF community when soil properties were calculated as the covariate matrix, suggesting that the correlation between oboveground vegetation and AM fungi was dertimined by the interactions between plant and soil properties. Similar with AMF community composition, the phylogenetic beta diversity of AMF was mainly determined by soil properties and has no relationship with geographical distance, climatic factors, or plant community. The soil available phosphorus was positively correlated with AMF phylogenetic beta diversity, which suggested that enhanced soil available phosphorus would promote phylogenetic evolution of AMF. 2）The impact of land use on AM fungal diversity. Land use comversion from grassland to farmland has been documented as a main cause of grassland degradation in the farming-pastoral ecotone of northern China. Land use change has lead to significantly changes in aboveground plant community and soil properties, but its influence on soil microbial communities is still poorly understood. Here, we studied 50 paired samples of grassland and farmland covering a large area in northern China using 454 pyrosequencing to compare difference of AMF diversity and community composition between these two land use types. At the same time, we used the multivariate statistics to address what are the factors that potentially best explain this influence. Totally we detected 101 OTUs in this area, which belonged to 11 genus of AMF.The dominant genera in grassland and farmland were found to be significantly different: in grassland Glomus was on average the most abundant genus with a proportion up to 69.13%, whereas in farmland both Glomus and Septoglomus were dominant genera with the proportions of 35.60% and 23.61% respectively. In addition,at genus level more sequences were obtained belonging to Glomus in grassland, while Funneliformis, Septoglomus and Claroideoglomus were proportionally more abundant in farmlands. This is the first time we clearly demonstrated the AMF difference in genus level between farmland and grassland. Moreover, 30 OTUs of AMF found to be sigificant ―indicator species‖ of grasslands or farmlands. Of these, 19 were more abundant in grasslands than in farmland and 11 OTUs were significantly more abundant in farmlands. These foundings provided basic information of AMF taxa for their future application both in grassland restoration and farming production. Land use conversion from grassland to farmland significantly reduced AMF richness and extraradical hyphal length density, and these land use types also differed significantly in AMF community composition. SEM showed that effects of land use on AMF richness and abundance in soil were primarily mediated by available phosphorus and soil structural quality. Soil texture was the strongest predictor of AMF community composition. Soil carbon, nitrogen and soil pH were also significantly correlated with AMF community composition, indicating that these abiotic variables may be responsible for some of the community composition differences among sites. |
| 公开日期 | 2015-07-07 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/15726]  |
| 专题 | 生态环境研究中心_城市与区域生态国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 向丹. 我国北方农牧交错带AM真菌多样性及其驱动因子研究[D]. 北京. 中国科学院研究生院. 2014. |
入库方式： OAI收割
来源：生态环境研究中心
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