生物土壤结皮层丛枝菌根真菌(AMF)群落结构多样性及其驱动机制研究

Arbuscular mycorrhizal fungi (AMF), a bridge between soil and plant roots, are abundant in soils of most ecosystems and play important roles in ecosystem stability, productivity and plant biodiversity. Biological soil crust (BSC) is an essential part of desert ecosystem. However, few studies on AMF diversity and function in BSC are found due to the restriction of symbiosis conclusion of AMF and vascular plant root system in the previous research. Lack of AMF knowledge in BSC results in significant reduction of their importance assessment in desert vegetation restoration and ecosystem stability. So in the present study, our aim is to explore the establishment of arbuscular mycorrhizal fungal assemblages in the development process of BSC by fluorescence in situ hybridization and metagenomics, and AMF community diversity of BSC in different climatic zones, different desert patch habitats and different BSC successional stages through high throughput sequencing. We want to investigate the driving mechanism of AMF diversity variations in desert ecosystem through examining the vegetation types, climatic factors and soil physicochemical properties. This research will elucidate the potential function of AMF in BSC and desert ecosystem, explain the function mechanism of BSC as "desert ecosystem engineer", and provide scientific basis for accelerating the restoration process and developing effective management measures of desert vegetation.

丛枝菌根真菌(AMF)广泛分布于各种陆地生态系统，是连接土壤和植物根之间的桥梁，在增加生态系统的生物多样性、保持生态系统稳定性、提高生态系统可持续生产力等方面发挥着重要作用。前期研究基于AMF与维管束植物根系专性共生的认识，限制了对荒漠生态系统重要组成部分的生物土壤结皮(BSC)层AMF及其功能研究，因而严重低估了AMF在荒漠植被恢复和荒漠生态系统稳定性中的重要性。本项目拟采用荧光原位杂交和宏基因组学等技术研究BSC演替过程中AMF联合体的结构和形成过程，高通量测序技术研究BSC层AMF群落结构在不同生物气候区、不同荒漠斑块生境、不同BSC发育阶段的多样性特征，并结合植被类型、气候因子与土壤理化性质的差异，探明AMF多样性变化的驱动机制，揭示AMF多样性在BSC及整个荒漠生态系统中的潜在功能，阐释BSC作为“荒漠生态系统工程师”的作用机理，为加速荒漠植被恢复和制定有效管理措施提供科学依据。

该项目分析了不同生物气候区（库布齐沙漠、毛乌素沙地、腾格里沙漠和古尔班通古特沙漠）BSC发育过程中AMF群落结构多样性特征以及AMF联合体的形成过程，观察了AMF群落孢子形态结构多样性特征与共生寄主苔藓体内囊泡形态及分布特征；对比了不同生物气候区以及荒漠斑块生境下不同斑块AMF群落结构的差异，并与土壤理化特性、土壤酶活性等环境因子进行了相关性分析，阐释了AMF多样性变化的驱动机制；研究了BSC AMF群落在碳、氮、磷循环过程中发挥的功能，揭示了AMF多样性在BSC及整个荒漠生态系统中的潜在作用。研究结果表明，AMF在隐花植物茎叶体的不同部位都有联合体形成，地衣、藓类结皮及其下层土壤AMF群落丰富度和多样性均表现为：藓类结皮下层土壤>地衣结皮下层土壤>藓类结皮>地衣结皮；BSC中AMF优势物种主要为球囊霉目、类球囊霉目和多样孢囊霉目，属水平以球囊霉属、类球囊霉属、盾巨孢囊霉属、巨孢囊霉属为主。荒漠不同斑块间AMF群落多样性具有显著的差异，多样性由高到低以此为：灌丛˃藓类结皮˃地衣结皮˃裸地；不同生物气候区BSC AMF群落优势物种差异显著，但多样性差异并不显著，与环境因子关系密切，微生境差异引起的土壤理化特性和微生物群落组成的影响较大。BSC AMF群落促进了碳、氮、磷生物地化循环过程，这些过程反过来提升了土壤质量，维持了荒漠生态系统的稳定。