| Soil salinization is one of the main ecological and environmental problems faced by the Yellow River Delta,and it is also an important factor affecting and restricting the healthy and sustainable development of the regional ecosystem.There is a close relationship among soil,plants and microorganisms.Salinized soil can affect the composition and function of plant community by affecting microbial activities and soil properties.Therefore,clarifying the driving mechanism of microbial community and its ecological effects has always been an important field of biochemical earth cycle research.However,the comparison of soil microbial community characteristics and microbial driving mechanism between different types of halophyte species,between rhizosphere and bulk of the same halophyte,and between different salt concentration conditions in rhizosphere soil of the same plant are not well understood.Therefore,this study selected three types of halophytes in the Yellow River Delta as the research objects: salt repellent plant Phragmites communis,salt accumulating plant Suaeda salsa,salt secreting plant Aeuropus sinensis,used high-throughput sequencing technology and instrumental analysis technology,studied the chemical properties of rhizosphere and bulk soils of typical halophytes,discussed the interaction between microbial community characteristics of rhizosphere soil and soil chemical properties.From the aspect of rhizosphere microbial regulation,it provided a theoretical basis for saline alkali soil improvement and saline alkali land vegetation restoration.The main research conclusions showed that:(1)At low salt concentration,soil pH range was 8.43-8.77,the pH of the rhizosphere soil of S.salsa was significantly higher than that of its bulk soil,the difference of rhizosphere soil pH of three different halophytes was as follows: S.salsa = P.communis > A.sinensis,which showed that A.sinensis was more obvious in reducing soil pH than S.salsa and P.communis;Under moderate salinity,soil pH range was 7.51-8.19,there was no significant difference between the rhizosphere and bulk soils of the three halophytes.The rhizosphere soil pH of the three halophytes decreased significantly with the increase of soil salt concentration.(2)Under low salt concentration,the range of soil TC,TN,aP,OC content was: 19.64-31.12 g/kg,0.48-1.29 g/kg,7.40-40.85 mg/kg,5.20-8.21%;the contents of TC,TN and aP in P.communis,S.salsa and A.sinensis rhizosphere soil were significantly higher than those in bulk soil,and the content of aP in S.salsa rhizosphere soil was significantly higher than that in P.communis and A.sinensis;The OC content in P.communis rhizosphere soil was significantly lower than that in bulk soil,and the OC content in A.sinensis rhizosphere soil increased significantly.The OC content of three plant rhizosphere soil was A.sinensis > S.salsa >P.communis.Under medium salt concentration,the range of soil TC,TN,aP and OC content was: 18.28-31.56 g/kg,0.32-1.17 g/kg,9.08-24.98 mg/kg,4.31-11.43%;the contents of TC,TN and aP in S.salsa and A.sinensis rhizosphere soil were significantly higher than those in bulk soil,while the content of OC in A.sinensis rhizosphere soil was significantly lower than that in bulk soil;The content of OC had no significant difference among the three plant rhizosphere soils.With the increase of soil salt concentration,the content of TC in S.salsa rhizosphere soil increased significantly,and the contents of OC and aP decreased significantly.(3)Under low salt concentration,the Shannon index of bacteria in rhizosphere soil was significantly higher than that in bulk soil;Under medium salt concentration,the bacterial community diversity(OTU,Chao1,faith)of A.sinensis bulk soil was significantly greater than that of its rhizosphere soil,and the bacterial community diversity of P.communis and S.salsa rhizosphere soil was significantly greater than that of A.sinensis rhizosphere soil.With the increase of salt concentration,the diversity of bacterial community and Shannon index in the rhizosphere soil of S.salsa and A.sinensis decreased significantly.(4)Proteobacteria and Actinobacteria were the dominant bacteria in all sample soils.The predominant phyla in the bulk soil of S.salsa at low salt concentration increased Chloroflexi more than those in the rhizosphere soil.With the increase of soil salinity,the dominant bacteria in the P.communis rhizosphere soil increased the Bacteroidetes,S.salsa rhizosphere soil increased Chloroflexi and Bacteroidetes,P.communis and S.salsa tended to select and form similar rhizosphere soil bacterial community structure to cope with the salt stress of plants.The ability of plant rhizosphere soil to resist external environmental disturbance and restore,as well as the categories of core key bacteria in plant rhizosphere soil have also increased.(5)Soil pH and aP was important influencing factors of soil bacterial community structure under low salinity conditions,soil pH and salinity was the main influencing factors under medium salinity conditions,and pH,aP and salinity was the main influencing factors of rhizosphere soils with different concentrations of three plants quantity.Under low salinity,there was a positive correlation between Proteobacteria and soil pH,and a negative correlation with TC,TN,and OC.The Bacteroidetes was positively correlated with TC,TN,aP and OC;Chloroflexi was negatively correlated with aP and pH,Actinobacteria was negatively correlated with pH,and positively correlated with TC,TN and OC;Under moderate salinity,the Proteobacteria was negatively correlated with pH,the Bacteroidetes was negatively correlated with OC,and the Chloroflexi was positively correlated with TC,TN,aP,OC,pH,and negatively correlated with salinity.Actinobacteria were positively correlated with OC,TC,TN,pH,and negatively correlated with salinity.The dominant functions of soil bacteria were chemoheterotrophy and aerobic chemoheterotrophy.(6)The dominant phylum of different halophytes was Glomeromycota,and the dominant genus was Scutellospora.Under low salinity,pH was an important factor affecting soil fungal community structure.Under medium salinity,the main influencing factors were salinity and TN.The main influencing factors in rhizosphere soils with different concentrations of three plants were pH and aP.The fungal community diversity in the rhizosphere soils of the three plants was significantly higher than that in the bulk soils;the fungal diversity and richness in the rhizosphere soils of P.communis and S.salsa increased significantly with the increase of salinity,the A.sinensis had no significant changes above.Under low salinity,the Glomeromycota was negatively correlated with soil OC and aP contents,and positively correlated with soil TC,TN,OC,and aP under medium salinity conditions. |
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