Effects Of Clonal Integration And Crude Oil Pollution On Soil Microbial Communities Of Phragmites Australis Wetland In The Yellow River Delta

Clonal integration refers to resource translocation and sharing between ramets of clonal plants connected by horizontal structures.Clonal integration can not only improve the tolerance of ramets to environmental stress,but may also affect soil physicochemical properties and microbial communities in soil around ramets.However,studies on the effects of clonal integration on soil micarobial communities and physicochemical properties are still lacking around the world.Crude oil pollution is one of the environmental problems faced by the Yellow River Delta,which can significantly affects its soil microbial communities and physicochemical properties.In order to study the effects of clonal integration and crude oil contaminant on soil microbial communities and phicochemical properties,provide theoretical support for bioremediation of oil pollution.We conducted a field experiment in a wetland dominated by Phragmites australis in the Yellow River Delta,China.0,5 or 10 mm thick crude oil were added to a 60 cm diameter circular plots of P.australis community to simulate none,moderate,or heavy oil contamination,and kept the rhizome connections between the ramets of P.australis inside and outside the plots severed or not,to prevent or allow clonal integration.The experiment started in 2014.In October 2016,we collected soil samples in the plots,and measured soil physicochemical properties,microbial communities of soil.The main results are as follows:(1)Crude oil contamination significantly increased the proportion of large macroaggregates,pH,organic carbon,total nitrogen and polyphenol oxidase activity,and decreased the proportion of microaggregates and electric conductivity.Clonal integration significantly increased the electrical conductivity and N/P,but decreased pH and catalase activity.There was a significant interaction effect between clonal integration and oil contamination only on soil electric conductivity.The pH was greater than 8,and electrical conductivity was greater than 0.60 mS/cm,which indicated that the research area was saline-alkali soil.(2)High-throughput sequencing results showed that the microbial community composition and dominant microbial groups were similar under different treatments,which mainly belonging to Proteobacteria,Actinobacteria,Chloroflexi,Acidobacteria,and Bacteroidetes.The abundance of Proteobacteria(36%-61%)increased with the crude oil addition,and it mainly caused by an increase in the abundance of y-proteobacteria and(3-proteobacteria;the abundance of Actinobacteria was small,and abundance of most other bacteria was decreased.The oil pollution significantly increased the abundance of the Alcanivorax,while the abundance of Nitrosomonadaceae increased first and then decreased.Clonal integration significantly reduced the abundance of Pseudomonas,Nitrospira and Nitrosomonadaceae.The interaction between clonal integration and petroleum contamination had no significant effect on each functional bacteria.(3)Crude oil contamination significantly affected the alpha-diversity of soil microbial.Moderate contamination increased microbial diversity,but heavy contamination decreased microbial diversity.The soil microbial beta-diversity indicated that the soil microbial community of rhizome severed and connected were more similar,and soil microbes with different under different oil addition.(4)Soil microbial community were significantly correlated with the proportion of large macroaggregates and microaggregates,total carbon,organic carbon,C/N,C/P and polyphenol oxidase activity.The proportion of large macroaggregates,total carbon,organic carbon,C/N,C/P and polyphenol oxidase activity were beneficial to the growth of Proteobacteria,Bacteroidetes and Alcanivorax,but not conducive to the survival of most other microorganisms.This indicated that crude oil and the changes in soil physicochemical properties caused by oil entry into the environment were conducive to the growth and reproduction of petroleum-degrading bacteria.Changes in soil pH and electrical conductivity caused by clonal integration and crude oil contamination significantly affected the Pseudomonas and Nitrosomonadaceae.Clonal integration and crude oil pollution could affect soil microbial community composition and soil physicochemical properties of P.australis wetland in the Yellow River Delta.Crude oil contamination reduced soil microbial community diversity and increased the abundance of some oil-degrading bacterials.Clonal integration was beneficial to improve the growth and tolerance of clonal plants subjected to oil pollution stress,thereby improving soil physicochemical properties and the degradation ability of oil-degrading bacterials to petroleum hydrocarbons.Changes in soil nutrients by clonal integration affected the growth of bacterial functional group associated with nitrogen turnover.Thus,the influence of clonal integration on soil microbial communities and physicochemical properties around the stressed ramets may further affect the ecological advantages of clonal plants.