Distribution And Co-occurrence Patterns Of Soil Bacteria In Typical Vegetation Of Coastal Wetland In The Yellow River Delta

The Yellow River Delta is the largest and most complete wetland in northern China,with complete vegetation succession sequence.Soil bacteria in wetland is a research hotspot in the field of ecology.The distribution patterns of soil bacteria are affected by vegetation type and soil depth.Through complex interactions,co-occurrence networks can be formed among bacteria,and the abundant taxa and rare taxa of bacteria have different distribution patterns and relative status.The study on the distribution and co-occurrence patterns of soil bacterial community of coastal wetland in the Yellow River Delta can deepen the understanding of wetland ecological process and provide theoretical support for ecological protection and restoration.Our study chose the soil and soil bacteria at four depths(0-10 cm,10-20 cm,20-30 cm,30-40 cm)in four typical vegetation Suaeda salsa,Tamarix chinensis,Phragmites australis and Spartina alterniflora of the Yellow River Delta as research objects.Combined soil physicochemical properties with microbial high-throughput sequencing technology,the distribution and co-occurrence patterns and their environmental influencing factors of soil bacterial communities were explored,and the distribution pattern and relative status of abundant taxa and rare taxa were discussed.The main results and conclusions are as follows:(1)Vegetation type rather than soil depth affected the distribution of soil bacteria.During the succession from S.salsa to T.chinensis then to P.australis,the composition of soil bacteria in P.australis community was different from the other two communities.The soil bacterial community α-diversity in S.alterniflora community was significantly higher than other communities.In terms of bacterial community composition,more bacteria,such as SEEP-SRB1 and Sulfurimonas,related to sulfur metabolism,were enriched in the soil of S.alterniflora community,which was significantly different from the other three communities.(2)The environmental influencing factors of soil bacterial community diversity in different vegetation types were different.In S.salsa community,the soil bacterial community diversity was mainly affected by soil dissolved organic carbon content and total organic carbon content.The diversity of soil bacteria community in T.chinensis community was mainly related to soil pH value and electrical conductance.Soil depth was the key factor affecting the diversity of soil bacterial community in P.australis community.The contents of nitrate nitrogen.ammonium nitrogen and total nitrogen were the key factors driving the diversity of soil bacterial community in S.alterniflora community.(3)Vegetation type changed the co-occurrence pattern of soil bacteria.In the four plant communities,soil bacteria mainly had positive interaction,and the negative interaction was the strongest in P.australis community,while the invasion of S.alterniflora enhanced the complexity and stability of soil bacterial co-occurrence network.Environmental factors could affect the construction of co-occurrence network.In S.salsa community,soil pH value and ammonium nitrogen content were the main factors affecting the soil bacterial co-occurrence network characteristics.In T.chinensis community,soil moisture content,pH value,electrical conductance,total nitrogen content,total phosphorus content content and total organic carbon content could change the soil bacterial co-occurrence network characteristics.In the P.australis community,the total nitrogen content could affect the soil bacterial co-occurrence network characteristics.The key factors affecting the soil bacterial co-occurrence network characteristics in S.alterniflora community were pH value,nitrate nitrogen,ammonium nitrogen content and total phosphorus content.(4)The abundant taxa and rare taxa of soil bacteria had different distribution patterns.Abundant taxa accounted for a low proportion but had high abundance,while rare taxa accounted for a high proportion but had low abundance.The two types of taxa changed with vegetation types,and the abundant taxa were more sensitive to environmental change.Futhermore,abundant taxa occupied a more central position in the co-occurrence network than rare taxa.The results of this study provide data and theoretical support for better understanding the distribution pattern and interaction of soil bacteria and their responses to environmental factors of coastal wetland in the Yellow River Delta.