| The disorder of soil nutrient cycling is one of important cause of soil fertility decline.Soil microbial communities play an important role in soil nutrient cycling.Phosphorus is an important nutrient element for plant growth and development.Therefore,studying the microbial communities' evolution dynamic related to phosphorus cycling will help to clarify the microecological mechanism that the effect of successive-planting and rotation on soil phosphorus cycling in poplar plantation,and provide a theoretical basis for managing plantation scientifically.The metagenome sequencing was used to compare the difference of six soil samples,the rhizosphere soil of the first and the second rotation poplar plantations(RSP1,RSP2),the bulk soil of the first and the second rotation poplar plantations(BSP1,BSP2),the soil of rotated peanut field(RPS)and the abandoned land soil after poplar clear cutting(ALS)on phosphate-solubilizing microbial community and phosphorus metabolism in a poplar plantation.The results showed that:(1)5 kinds of phenolic acids which included p-hydroxybenzoic acid,benzoic acid,cinnamic acid,vanillin and ferulic acid were detected in the soil of poplar plantations of successive-planting and rotation.The total content of phenolic acid presented the regularity of RSP2 and BSP2 >RSP1 and BSP1 > RPS > ALS.Soil physical and chemical properties varied in different soil samples.Organic matter,pH and available K showed significant difference while there was no significant difference in total P,available P and available N.(2)8 phyla were found in different soil samples which were Firmicutes,Proteobacteria,Actinobacteria,Acidobacteria,Bacteroidetes,Chloroflexi,Verrucomicrobia and Planctomycetes with Firmicutes,Proteobacteria and Actinobacteria being the dominant.Rotation reduced microbial community diversity.The diversity of soil microbial community in the second poplar plantation was lower than that in the first poplar plantation,but the difference did not reach the significant level.Compared with the first poplar plantation,soil microbes changed significantly at the genera level,and microbial species decreased in second poplar plantation,RPS and ALS,and the microbial community structure changed.The total abundance of functional genes presented the regularity of RSP1 and BSP1 > ALS > RSP2 and BSP2 > RPS.After successive-planting,the abundance of translation,ribosomal structure and biogenesis,replication,recombination and repair,secondary metabolites biosynthesis,transport and catabolism functional genes decreased.There was no significant change in the abundance of functional genes after second poplar plantation clear cutting.(3)Microorganisms from nine genera were related to phosphorus cycle in different soil samples which included 7 genera of Bacteria,Bacillus,Pseudomonas,Flavobacterium,Paenibacillus,Bradyrhizobium,Pantoea,and Serratia,2 genera of Actinomycetes,Streptomyces,and Arthrobacter.Bacillus and Pseudomonas were the dominant.Pantoea,Paenibacillus,Serratia were the unique flora in the first poplar plantation,second poplar plantation,ALS respectively,but the proportion was less than 0.1%.(4)The proportion of phosphate solubilizing microorganisms in the first poplar plantation,second poplar plantation,RPS and ALS were 22.4%,23.1%,26.8% and 27.7% respectively.Compared with successive-planting,rotation could increase the number of phosphate solubilizing microorganisms.Compared with the first poplar plantation,the abundance of shared phosphorus solubilizing microorganisms in the second poplar plantation increased in different degrees.Compared with the second poplar plantation,the abundance of Bacillus and Pseudomonas were increased by 19.9% and 30.3%,20.4% and 71.4%,respectively,while abundance of Arthrobacter,Bradyrhizobium,Streptomyces reduced,and the decline was more than 50%.(5)The total abundance of phosphate solubilizing microorganisms in rhizosphere soil was significantly lower than that in bulk soil.Bacillus and Pseudomonas in rhizosphere soil were significantly higher than that in bulk soil,R/S values were 0.6~0.7:1 and 0.4~0.7:1,respectively while Arthrobacter,Bradyrhizobium,Streptomyces was significantly higher than that in bulk soil,the R/S value of bacteria was 4~7:1,and that of actinomycete was 2~ 6:1.(6)The total abundance of phosphatase gene presented the regularity of RSP1 and BSP1 > ALS > RSP2 and BSP2 > RPS.The total abundance of phosphatase gene in ALS was increased,and the RPS was the lowest among the samples after the second poplar plantation clean cutting.The R/S value in first and second poplar plantation were 1.39 and 1.09 respectively,and the difference in second poplar plantation between rhizosphere soil and bulk soil narrowed,and even lower phosphatase gene's abundance was shown in rhizosphere soil v.s in bulk soil.The abundance of phosphatase genes in rhizosphere soil of second poplar plantation was lower than that of in first poplar plantation.(7)Compared with the first poplar plantation,the intensity of organic phosphorus conversion in second poplar plantation decreased by 16.63% and successive-planting reduced the content of available phosphorus in soil.Compared with the second poplar plantation,the intensity of organic phosphorus conversion in RPS increased by 32.36%,and that of in ALS increased by 25.44%.Rotation and abandonment could increase the availability of phosphorus in the soil and improve forest productivity... |
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