Research On The Diversity And Impact Factors Of Soil AM Fungi In Typical Karst Area

The ecosystems in Karst regions are usually vulnerable to human disturbances in a way similar to those located at the edge of deserts.Due to the unreasonable use of land by human,the Karst region in southwest China has experienced serious ecological degradation and decline.Therefore,efficient vegetation restoration should be implemented in order to improve the ecosystem services in this region.Arbuscular mycorrhizal(AM)fungi in soil are symbiotically associated with the roots of more than 80% of plant species on earth.They supply soil nutrients and water to plants,which enhance resistance and establishment of plants.Therefore,studies on the AM fungi diversity and function were very important for understudying soil ecological processes in fragile ecosystems.In this study,the Karst peak-cluster-depression region of Duan county territory of Hechi city of Guangxi was selected,based on the investigation of environmental heterogeneity,using High-throughput sequencing technology and other modern molecular biology techniques to research the communities and its impact factors of AM fungi at the secondary forest ecosystem,the vegetation recovery phase,and the county scale level.The results will provide the scientific basis for the vegetation restoration of degradation habitats in Karst region.The main results are as follows:(1)At the level of secondary forest ecosystem,the results showed that the lithology significantly changed the composition structure of AM fungi,but the slope position had little effect on the composition structure of AM fungi.Under different lithology conditions,the difference of AM fungi community composition and dominant OTU were significant.Under different slope position conditions,there was no significant difference in the community composition and dominant OTU of AM fungi.There was no significant difference in AM fungi diversity under different lithology and slope position conditions.RDA analysis showed that the silt content of soil,the exchange of magnesium ions,the pH,the exchange of calcium ions and the organic carbon had significant differences on the community composition of AM fungi.The results show that different lithology and slope position conditions affect the community composition and diversity of AM fungi.(2)At the level of vegetation restoration stage,the content of soil nutrient content varies in different lithology and vegetation types.The diversity of AM fungi is the largest in the grass ecosystem under the conditions of dolomite,and is the smallest in the farmland ecosystem.Under the condition of limestone,the secondary forest ecosystem is the largest,and in the farmland ecosystem is the smallest.There were significant differences in the community composition of AM fungi in different lithology and vegetation types.Lithology,vegetation types and the interaction between lithology and vegetation types were significantly correlated with the AM fungi diversity index.Redundancy analysis showed that the sand content of soil,the exchange of magnesium ions,the available phosphorus,the total phosphorus and the total potassium had significant differences on the community composition of AM fungi.The results show that in the level of vegetation restoration stage,the change of the community composition and diversity of AM fungi is the result of the interaction between vegetation and soil physical and chemical properties.(3)At the level of county scale,further research on comparative analysis of community composition structure of AM fungi and diversity influenced by the lithology,vegetation types and the interaction between lithology and vegetation types,found that the lithology,vegetation types and their interaction with AM fungi diversity index was significantly correlated.There were 181 OTU belonging to 11 AM fungi,suggesting that AM fungi have abundant species diversity.Redundancy analysis showed that the soil physical and chemical factors affecting on the community composition and diversity of AM fungi were different under different lithology and vegetation types conditions.Thus,we should consider not only the effect of vegetation types but also lithology on the AM fungi diversity,when AM fungi are used to recovery vegetation in Karst region.