Study On The Feedback Mechanism Of Mycorrhizal Fungi On Dominant Plants In Different Restoration Succession Stages Of Typical Steppe

Grassland is one of the important terrestrial ecosystems in our country.It is known as the"skin"of the earth.Its ecological status is very special.It has important ecological functions such as water conservation,soil and water conservation,wind and sand fixation,and climate regulation.However,in recent years,my country’s grasslands have been degraded to varying degrees.Among them,the typical grasslands in Inner Mongolia have been severely degraded due to overgrazing,their production functions have declined sharply,and their ecological functions have become increasingly fragile.At present,the search for the degradation mechanism and restoration methods of grassland has become a research hotspot in grassland ecology.Among them,the role and mechanism of microbial-mediated plant-soil feedback in the succession of grassland communities have gradually attracted the attention of ecologists.However,most of the feedback studies so far have considered the rhizosphere microorganisms as a whole,analyzing the collective effects of a variety of microorganisms,even including the physical and chemical properties of the soil,and the specific feedback rules and mechanisms for key microbial groups are still fuzzy.Among the complex and diverse rhizosphere microorganisms,arbuscular mycorrhizal fungi（AMF）has become the focus of current research on microbial-plant interaction due to its unique biological and ecological characteristics.Research on the effects of AMF-plant mutual feedback on grassland restoration and succession is still relatively scarce,and there is a lack of understanding of the driving mechanism of key microorganisms in the succession of grassland ecosystems.Therefore,this study takes representative plants of different succession stages in the typical temperate grasslands of Inner Mongolia as the research object,and through experimental settings such as field sampling,host induction,cross-connection and isotope labeling,in order to answer the following scientific questions:（1）Different succession Can stage plants induce the formation of AMF communities with different compositions?（2）Can AMF give feedback to plants in different succession stages?（3）What is the functional mechanism of AMF-plant feedback that changes with plant succession stages?By revealing the above scientific problems,the feedback effect of mycorrhizal fungi on dominant plants at different succession stages can be clarified.The main findings are as follows:1.There are 7 families and 10 genera of AMF found from 15 plants commonly found in typical grasslands of Inner Mongolia.Among them,Glomus is the dominant genera in 15plants,and the relative abundance of other genera is different in different plants.It shows that the symbiotic relationship between AMF and host plants has a certain preference.2.The sequencing results of the root system and root soil AMF communities of six representative plants at different succession stages showed that the AMF species richness of the early succession plant Artemisia frigida was the highest.Network analysis showed that most of the fungi did not show host preference,and the fungi that showed host preference were mostly occasional species.AMF showed strong nesting and low modularity characteristics.3.Dominant plants at different stages of restoration succession can induce different AMF communities and have a significant impact on plant growth.Through the analysis of the feedback coefficient,the AMF community can promote the development of the succession direction of grassland restoration,and explain the succession of plants in the process of grassland restoration from the perspective of underground microorganisms.4.The inoculation of the AMF community can significantly improve the absorption of N and the curing of C by plants.The curing amount of ¹³C by plants accounts for more than25%of the total labeling amount,and the absorption of ¹⁵N is relatively small,which is only the total labeling amount.1.3-4.2%.In summary,this study studied the feedback effect of typical steppe mycorrhizal fungi on dominant plants at different succession stages and found that inoculation of non-homologous AMF in late succession plants can form positive feedback on their nutrient absorption and biomass.Inoculation of early plants will produce negative feedback.In the process of plant community succession,the feedback effect of AMF community on plants is that the plant community changes from early successional plants（Cryptanthus scabra,Artemisia frigida）to late successional plants（Lymus chinensis）is an important driving mechanism for succession;and under the condition of inoculating homologous AMF communities,plant species at different succession periods are affected by negative feedback.AMF reduces the ecological range of dominant species by inhibiting plant growth and nutrient absorption capacity.Provide more niche space for non-dominant plants to maintain the diversity of typical grassland plant communities;in addition,the dominant genera（Glomus）of the AMF community from different plant species sources are basically the same,but the non-dominant species are quite different,and they are The service functions provided by different plant species exist.Therefore,rare species may have an important regulatory effect on the function of the AMF community.Future research should increase the ecological functions of the rare species in the AMF community,so as to enhance the understanding of the ecological functions of AMF.It provides theoretical support for the application of AMF to the management and degradation of grassland ecosystems.