Research Of Arbuscular Mycorrhizal Community In Different Vegetation Succession Stage Of Songnen Saline-alkali Grassland

Soil salinization has become a global problem restricting the development of husbandry and the construction of surface landscape.Songnen Plain,which the major grain producing area and the important vegetation-covered area,has been affected by salinization seriously in recent years.Arbuscular mycorrhizal(AM)fungi are widely distribute in various habitats,such as salt-alkali soils.Many studies have confirmed that AM fungi can significantly improve the salinity tolerance of hosts and the fungi were isolated in Songnen saline-alkali grassland.However,the community structure changed with the variational environmental conditions,and the corresponding functions of community will vary.To explore the response of AM fungal community composition and colonization to vegetation succession in saline-alkali grassland,the rhizosphere soil and roots of three stages in Songnen saline-alkali grassland were selected as the research objects.The main research results were as follows:(1)The soils in three succession stages were disturbed by salinization heavily,and the cumulative contribution of soil p H,salt content and carbonate concentration to soil quality differentiation among three vegetation succession stages was 25.64%.Besides,the value of the three salinization indices decreased significantly as the order of the Suaeda glauca,Puccinellia tenuiflora and Leymus chinensis,soil properties gradually improved.(2)3916 ASVs were obtained from the three succession stages by high-throughput sequencing technology,and Glomus was identified as the dominant genus.The composition of AM fungal community differed among three stages,and significantly enriched or reduced species presented at every phase,but there were similarities in the first and second stages of succession(S.glauca,P.tenuiflora).(3)A total of 58 species in 17 genera were identified by morphological method.The Glomus has the largest number of species,and sp1 was determined as the dominant species in the succession with the isolation frequency,relative abundance,and importance value of 100%,18.1%,and 59.1%,respectively.The analysis revealed that the highest diversity of AM fungal community presented at the L.chinensis stage,however,Par.occultum,A.morrowiae,Am.Reticulata,R.clarus,R.aggregatus and C.walkeri significantly enriched at S.glauca stage and P.tenuiflora stage.(4)Soil properties played an effect on AM fungal community composition and species distribution.The analyses results showed that soil drove the variation of AM fungi among vegetation succession stages,among which,p H exerted the strongest driving effect.Moreover,the abundance of R.aggregatus was positively correlated with soil p H,EC value and carbonate concentration,indicating that it might have strong saline-alkali tolerance.(5)The plants’ communities of the three stages could be colonized by AM fungi in the field,and the changes of AM fungal colonization and spore production were driven by soil properties,among these soil indices,p H played the strongest effect.Except for the colonization rate,the colonization intensity,vesicle abundance,arbuscular abundance and spore density were not significantly different in the first two stages.The sp1 was temporarily named as Glomeraceae sp1 in this study basing on the sequencing for 18 S r DNA of the dominant AM fungi.Subsequently,the mycorrhizal structures of the host were found in the roots of S.glauca,P.tenuiflora and L.chinensis after the monospore culture for the dominant species,speculating Glomeraceae sp1 successfully colonized the vegetation in field.The salinization of Songnen saline-alkali grassland was still serious at present,and the soil in all the three important succession stages degraded severely.Nonetheless,with the progress of vegetation succession,soil quality improved and the AM fungi community in three stages showed differences.The largest species number appeared at L.chinensis stage,the community composition in the third stage significantly differed from the initial two stages,while that showed certain similarities among S.glauca and P.tenuiflora,and so were the changes of mycorrhizal colonization and sporulation in three stages.The exploration results also indicated that the variation of AM fungi community were driven by soil factors,in which p H exerted the most significant role.Besides,it was proved that the dominant fungi(Glomeraceae sp1)might play an important role in the field.