The Influence Of Lake Recovery On Soil Biological Activity And Microbial Community Structure In Poyang Lake Area

The Poyang Lake wetland plays an important role in climate regulation,water sources conserving,water purifying and biodiversity maintenance.However,excessive reclamation may cause degradation and reverse succession of ecological environments.Therefore,lake recovery has become an important measure for ecological restoration in Poyang Lake wetland.Soil microorganism is an essential component of soil functions could be considered as an indicator of ecosystem conversion.Thus,studying the changes of microbial community structures and soil biological activities after reclamation and restoration is benefit to formulate scientific and reasonable wetland restoration policies.In this study,the typical reclaimed land uses:vegetable fields,abandoned wetlands,rice fields and pond soils with 38 years of reclamation in Poyang Lake wetlands were selected as the research objects.The high-throughput sequencing and soil enzymes were used to investigate the changes of soil bacterial community structure and soil biological activities after reclamation.Then,the soil samples in restored wetlands that converted from rice fields 15,20,and 40 years ago were selected,and rice fields and natural wetland soils were also sampled as controls.This experiment aimed to explore the succession of bacterial and fungal communities along with the years of restoration.Noteworthily,the soil aggregates provide different microenvironments for microorganisms.Moreover,rare bacterial community plays an important role in ecosystem functions and has been shown to enhance the functionality of the abundant taxa.The spatial distribution and regulation mechanisms of rare species are often different from those of abundant bacteria.Therefore,we further investigate the abundant and rare bacterial communities in natural wetlands,rice fields and restored wetland across different aggregates,comprehensively explore the responses mechanism of soil microbes to lake recovery.The results are as follows:1.Different land uses after wetland reclaimed significantly affected the bacterial community structure and soil biological activity:?1?Rice fields and natural wetlands had similar bacterial community compositions,the dominant species were Acidobacteriales,Holophagae,Planctomycetes and Spirochaetae.Vegetable fields and abandoned wetlands as upland soils had significantly higher abundance of Gemmatimonadates and Actinobacteria.The composition of permanently flooded pond soil had unique features and significantly enriched levels of Chlorobi.The results suggested that bacterial community composition was mainly affected by hydrological conditions.?2?The hydrolase activities were highest in rice fields,while the oxidase activities were highest in pond soils,and the enzyme activities in natural wetlands,vegetable fields and abandoned wetlands were always lowest.Compared with bacterial community structure,enzyme activity was more susceptible to soil physical and chemical properties.2.The responses of bacterial and fungal communities to the lake recovery were different:?1?The soil physical and chemical properties,biological activities and bacterial community structure in the 40-year restored wetland had been returned to the natural wetland.The dominant bacteria were Alphaproteobacteria and Actinobacteria.However,for the fungal community,although the dominant species were gradually recovering from Basidiomycota in rice fields to Ascomycota and Basidiomycota in restored wetlands,to Ascomycota in natural wetlands,the fungal community compositions were still significantly different among restored wetlands,rice fields and natural wetlands.The results suggested that fungi were more sensitive to land use changes than bacteria.?2?The bacterial community structure and function were mainly affected by soil nutrients,but pH was the most significant factor to fungal community.3.The responses of abundant and rare bacterial communities to lake recovery across different fraction aggregates sizes:?1?The rare bacteria wihtin aggregates were all significantly different among natural wetlands,rice fields and restored wetlands.However,the abundant bacterial communities associated in>2 mm aggregates were not significantly affected by lake recovery,and the abundant bacteria within the<2 mm aggregates were not significantly different between the restored wetlands and natural wetlands,suggesting that the abundant bacteria within large aggregates was not easily affected by environmental changes.It meant that rare bacterial communities were more sensitive to land transformation than abundant ones.?2?Rikenellaceae_RC9_gut_group,Alistipes,Ruminococcaceae_UCG-010,Ruminococcaceae_UCG-005 and Treponema₂ only showed the highest abundance in rice fields within>5 mm aggregates.Piscinibacter,Crenothrix,Byssovorax,Micromonospora and Phormidium only showed higher abundance in the restored wetlands than rice fields and natural wetlands within 0.25-2 mm and<0.25 mm aggregates.The results showed that the different sizes aggregates provided different microhabitats for microorganisms.?3?The abundant bacterial community was mainly determined by environmental factors,while the rare bacterial community may affect by a random process.Additionally,the abundant bacterial community within<0.25 mm aggregates played a positive effect on soil biological activity,while rare bacteria showed a negative effect.This indicated that abundant and rare bacteria might have different niches.Summarily,the different land use types significantly affected the microbial community structure and soil biology activity after wetland reclamation.After 40 years of recovery,the soil carbon mineralization rate and potential nitrification,bacterial community structure and function gradually recovered to the natural wetlands,whereas the fungal community still showed significant differences between restored wetlands and natural wetlands.Additionally,the bacterial taxa significantly affected by land uses were inconsistent within different aggregate sizes,and the responses of abundant and rare bacterial communities to lake recovery were inconsistent,suggesting that studying abundant and rare bacteria within each aggregate fraction would contribute to a deeper understanding of ecological functions of microorganisms in land conversion.