Effects Of PH On The Conversion Of Organic Carbon And Microbial Communities Structure In Red Soil And Alkline Soil

pH can change the mineralization rate of soil organic carbon,but the relationship between soil organic carbon mineralization and microorganisms under different pH conditions is still unclear.In this study,high-throughput sequencing and quantitative PCR were used to study the bacterial community structure and carbon transformation-related functions of pH in the Yingtan Agricultural Ecology Experimental Station and Fengqiu Agricultural Ecology Experimental Station of the Chinese Academy of Sciences.The impact of genes and their relationship to soil carbon conversion.Secondly,through the addition of ¹³C-glucose exogenous substances,the excitation effect of exogenous low molecular organic substances on soil under different pH treatments and its corresponding microbial mechanism were explored.The aim is to provide a theoretical basis for soil carbon sequestration in red soils and southern forests.By adding aluminum sulfate and lime to change the alkaline and red soil pH,four pH gradients were formed:alkaline pH 7.0（A7.0）,soil pH 7.8（A7.8）,and alkaline pH 8.5（A8.5）and alkaline pH 9.0（A9.0）;red soil pH 5.7（R5.7）,red soil pH 6.8（R6.8）,red soil pH 7.5（R7.5）,red soil pH 8.5（R8.5）.Among them,the alkaline itself has a pH value of 7.8,and the red soil itself has a pH of 5.7.The results showed that the cumulative CO₂emission of alkaline increased significantly with the increase of pH（P<0.05）,increased by 281%from pH7.0 to pH9.0,and the CO₂emission of red soil from pH 5.7 to pH 6.8 decreased significantly.After the significant increase,the increase from pH 5.7 to pH 8.5 increased by 29%;the soluble carbon content in alkaline and red soil increased significantly with the increase of ph,from pH to high pH increased by 208 mg and 240 mg,respectively;soil the ratio of soluble carbon to nitrogen increased significantly with the increase of pH（P<0.05）.The carbon content of alkaline was significantly higher than that of other treatments at pH 7.8.The content of microbial biomass carbon in red soil did not change significantly between different pH.The microbial biomass nitrogen content in red soil increased significantly with pH（P<0.05）;the carbon and nitrogen ratio of alkaline microbial biomass was significantly higher than that of other treatments at pH 7.8（P<0.05）,and red soil was highest at pH 5.7.In the alkaline and red soil,theαdiversity was the highest under the treatment of pH 7.0 and pH 6.8,respectively.The Bacteroides,Actinobacteria,Acidopbacteria and Proteobacteria were the dominant bacteria in all pH treatments,and the Bacteroides with pH the relative abundance increased gradually,and the relative abundance of Actinomycetes decreased with the increase of pH.Theα-Proteobacteria dominated the Proteobacteria,and the relative abundance increased with the increase of pH,and increased in alkaline and red soil.30.98%and 39.97%;RDA analysis showed that soil soluble carbon and soluble carbon-nitrogen ratios affected soil microbial community changes,and soil CO₂emissions were closely related to microbial community structure;quantitative PCR results indicated GH48 and carbon conversion-related GH48 in red soils.The abundance of cbhI functional gene increased significantly with pH（P<0.05）.The abundance of GH48 and cbhI functional genes in alkaline was significantly lower than that under high-pH treatment（P<0.05）.It was found that the excitation effect of ¹³C-glucose was different between different pH treatments.The red soil had the largest glucose mineralization and priming effect at pH 6.8,and the glucose had the largest mineralization and priming effect at pH 8.5;red soil under glucose addition the CO₂emission increased gradually,the CO₂emission of alkaline reached the maximum at pH8.5,and the soluble carbon content was larger at the high pH value.The microbial biomass carbon in alkaline alkaline was the smallest pH 8.5.The abundance of GH48 functional gene abundance in red soil was significantly lower than that in low pH（P<0.05）.The GH48 increased significantly with the increase of pH in alkaline and was the largest at pH8.5（P<0.05）and decreased at pH9.0.The soil microbes under glucose addition changed with the change of pH.The relatively abundant abundance communities wereα-Proteobacteria,γ-Proteobacteria and Bacteroides,and pH was positively correlated with the relative abundance ofα-Proteobacteria and Bacteroides.There was no significant change inγ-Proteobacteria between different pH.According to the PICRUST analysis,the abundance of the under glucose addition and the red soil associated with energy metabolism,polysaccharide metabolism and nucleotide metabolism under the treatment of pH 7.8 and pH 6.8 were the highest.