菌根真菌对内蒙古草原不同演替类型植物的反馈机制

Biotic and abiotic changes of soil properties caused by a plant may feedback to enhance or reduce the performance of the same plant species. The feedback between plant and soil has become an important concept for explaining the diversity, stability, dynamics and succession of plant communities. However, the patterns and mechanisms of feedback driven by key microbial groups such as arbuscular mycorrhizal fungi (AMF) remain unclear. In this proposed study, we plan to take advantage of a long-term grassland restoration platform established in 1999 on a degraded steppe in Inner Mongolia, aiming to explore the mechanisms underlying the formation of AMF-plant feedback. We will first examine the compositional differences among AMF communities associated with co-existing plant species that vary in their successional status trough a greenhouse training experiment. We will then set up a reciprocal inoculation experiment to cross each AMF spore community with its own host plant and other plants in order to examine the changing patterns of AMF feedback on plants of different successional status. Meanwhile, we will develop a novel 14C, 15N and 33P labeling method to quantify the nitrogen and phosphorus directly transferred to a host plant by AMF and the carbon allocated to the fungi by the same plant. Comparing the ratios of nutrient benefit versus carbon cost between plants reciprocally inoculated with own and foreign AMF communities would enable us to evaluate host-specific changes in the key function of AMF. If the functional variation between AMF hosted by different co-occurring plant species exists, it would provide the most direct evidence for AMF-driven plant-soil feedback. It would also help clarity how this particular group of soil microbes influence and respond to the dynamics of plant communities. Results from this study would help us gain a better understanding of the importance of plant-soil feedback in the maintenance of grassland biodiversity and stability.

根际微生物能够反馈影响群落中不同植物的生长，直接改变共存植物的相对竞争关系，推动群落结构的动态变化，因而对解释植物群落的演替进程和方向有着重要的意义。然而，关键微生物类群如丛枝菌根真菌（AMF）与宿主植物相互反馈的规律和机制尚不明晰。本项目以内蒙古退化草原恢复演替群落中代表不同演替类型的植物为研究对象，开展不同类型宿主植物对AMF的诱导以及AMF孢子与植物间的交互回接实验，通过分析不同来源AMF对不同类型植物生长的影响，揭示AMF对不同演替类型植物的反馈作用。同时，开展菌丝隔离及C-14、N-15和P-33标记实验，通过测定AMF与不同类型植物之间的N/C、P/C比，分析AMF主要生态功能在不同演替类型植物之间的特异性变化，揭示AMF-植物反馈的形成机制、作用规律及其对群落恢复演替过程的潜在影响。本研究不仅有助于发展植被-土壤反馈理论，还对退化草地恢复治理的实践有着指导意义。

本项目已经按照任务书完成了内蒙古温带典型草原恢复演替过程中植物群落与丛枝菌根真菌（AMF）的反馈关系及其机制的相关研究内容。通过野外调查取样结合温室控制试验应用交互接种和同位素标记等技术，本项目发现Glomus属是内蒙古温带草原的AMF优势属，其相对丰度在不同恢复演替阶段植物根系内都高于70%，并且氮沉降能够显著影响不同演替阶段代表植物根系内的AMF群落组成，其影响程度取决于宿主植物的种类。植物-AMF反馈研究结果表明，总体上AMF通过帮助植物吸收氮素等营养显著促进了植物生长，但是不同演替类型植物诱导形成的AMF存在明显的功能差异。演替晚期植物与AMF群落间的适配性最优，AMF群落能够为演替晚期植物提供正反馈，促进其优势度的提升；而演替中期和早期植物在一定条件下会受到AMF群落负反馈影响，生长受到抑制，且中期植物受到抑制程度比早期植物更强。因此，AMF能够为典型草原植物群落的正向演替提供驱动力。本项目已在包括Science of the Total Environment、Plant and Soil、Applied Soil Ecology、Frontiers in Plant Science等国内外学术期刊上发表研究论文13篇，授权国家发明专利2项，1项技术应用案例入选2021年中国科协“科创中国”平台，另有部分研究结果计划在2022年发表。