Influencing Factors And Microbial Impact Mechanism Of Soil Phosphorus Speciation Distribution In The Fluctuation Zone Of Poyang Lake

The protection of ecological environment in Poyang Lake area has always been a topic of concern for the government and the public,and the fluctuation zone has a significant contribution to the purification of pollutants in the lake area.In this study,the distribution characteristics of soil organic phosphorus and inorganic phosphorus morphology in different areas,soil layers and different parts of the fluctuation zone were studied,as well as the soil physical,chemical and biological factors that may affect their distribution,and the main soil factors affecting the distribution of soil phosphorus morphology in the fluctuation zone were clarified by correlation analysis and redundancy analysis.We selected the soil in the Fuhe River fluctuation with favorable soil water and fertility conditions,screened and purified the organic and inorganic phosphorus solubilizing bacteria,and reconnected them to the sterilized soil to study the mechanism of phosphorus solubilization,in order to provide data reference for the phosphorus pollution control of Poyang Lake and the research of phosphorus solubilizing bacteria.The main conclusions are as follows:1.The phosphorus content of different forms of soils in the fluctuation zone of Poyang Lake all have the law of decreasing with the deepening of soil layer,and the total organic phosphorus and total inorganic phosphorus content of soils in the sampling sites account for 18%-57% and 53%-94% of the total phosphorus of soils,respectively,and the average phosphorus content of Fuhe River is the highest.The content of organic phosphorus in different soil layers and in different parts of the soil in each fluctuation zone showed ML-OP > MR-OP > HR-OP > L-OP and inorganic phosphorus showed O-P > Fe-P >Al-P > Ca-P.The organic phosphorus with high activity in the 0-10 cm soil layer accounted for 72% of the total organic phosphorus on average,and the inorganic phosphorus with high effectiveness accounted for 47% of the total inorganic phosphorus on average.The four organic phosphorus contents of soils in the central part of Nanji Mountain,Ganjiang River and Xiuhe River fluctuation zone had a tendency to be higher than those in the upper part of the fluctuation zone,and all four inorganic phosphorus in Ganjiang River and Xiuhe River fluctuation zone were higher for soils located in the central part.2.Correlation analysis showed that soil p H,organic matter,total phosphorus,total nitrogen and alkaline nitrogen contents were significantly correlated with all four forms of organic phosphorus;soil moisture,organic matter,total phosphorus,fast-acting phosphorus,CEC and total nitrogen contents and soil nitrogen-phosphorus ratio were significantly correlated with all four forms of inorganic phosphorus.The results of redundancy analysis showed that soil factors explained 90.53% and 90.92% of the variation of soil organic phosphorus fraction and inorganic phosphorus fraction,respectively,among which soil total phosphorus,effective phosphorus content and pH were the main factors influencing the organic phosphorus morphology in the surface soil of Poyang Lake fluctuation zone,and the dominant microorganisms with high contribution to the organic phosphorus morphology mainly included Chloroflexi,Gemmatimonadetes and Bacteroidetes.Soil total phosphorus,effective phosphorus and alkaline nitrogen content are the most important factors affecting the inorganic phosphorus morphology in the surface soil of Poyang Lake fluctuation zone,and the dominant microorganisms with high contribution to the inorganic phosphorus morphology mainly include Chloroflexi,Actinobacteria and Nitrospirae.3.The screened phosphorus solubilizing bacteria were identified by 16 S rDNA molecular identification to obtain two genera of Pseudomonas and Burkholderia,among which X1 and X4 were both Pseudomonas viciae,but their growth states were affected under different growth substrates,resulting in differences in phosphorus solubilization effects.After the addition of phosphorus solubilizing bacteria to the soil,the total soil organic phosphorus showed a pattern of first decrease and then increase with time,while the total soil inorganic phosphorus showed a pattern of first increase and then decrease,L-OP and Fe-P and Ca-P all had a decreasing trend,and other forms of phosphorus and soil effective phosphorus content all fluctuated within a certain range with the change of incubation time.The soil acid phosphatase activity of organophosphorus solubilizing bacteria was greater than that of inorganic phosphorus solubilizing bacteria.X2 enzyme activity was slightly greater than that of X1 and much greater than that of X3,while in terms of the absolute amount of phosphorus solubilized,X1 had the strongest ability to solve organic phosphorus.The types and amounts of organic acids produced by different strains were different,and the types and amounts of organic acids secreted by organophosphate solubilizing bacteria were much lower than those of inorganic phosphate solubilizing bacteria.X4 secreted the most types of organic acids,but in terms of the absolute amount of phosphorus solubilized,X6 had the strongest ability to solve inorganic phosphorus.In summary,the phosphorus activity in the top soil of the fluctuation zone of Poyang Lake is high,and the risk of releasing to the water body is high.Increasing the area of river fluctuation zone or keeping high water level of river can effectively reduce the amount of phosphorus into the lake.If the soil in the fluctuation zone is used for agriculture during the dry period,the management should be strengthened,and the fertilizer made of efficient phosphorus solubilizing bacteria such as pseudomonas.extracted from the local area should be applied to increase the phosphorus supply capacity of the soil,which can better reduce the amount of phosphorus into the lake.