Distribution Characteristics And Influencing Factors Of Soil Organic Carbon In Different Cover/Use Types Of Wetland At The Confluence Of Hongze Lake And Huai River

Wetlands are an important part of the Earth's ecosystem,and wetland soil organic carbon pool is one of the largest in the world and plays an important role in the global carbon cycle.At present,China has proposed the goal of achieving carbonneutrality by 2030 and carbon neutrality by 2060,and actively promoted and implemented ecological protection and restoration projects.In the 2020 National Master Plan for the Protection and Restoration of Important Ecosystems,a large n?mber of wetland ecological conservation and restoration projects have been planned and implemented in the Yangtze and Yellow River basins for carbon sequestration of wetland ecosystems.Changes in carbon sources/sinks due to changes in soil organic carbon turnover can play an important role in global climate change,and wetland cover/utilization types have an important impact on the turnover and stability of soil organic carbon.The exploration of mechanism has become the hot spot of current scientific research.In view of this,we carried out ecological restoration projects in Hongze Lake Wetlands and carried out scientific research on soil carbon sequestration in wetlands.Located in the transition zone between the warm temperate zone and the northern subtropical region,The intersection of Hongze Lake and Huaihe River has specific climatic conditions and hydrological conditions,which have important effects on the physical,chemical composition and soil microbiome structure of soil organic carbon in wetlands in the region.Therefore,this paper takes the soil of wetland natural vegetation type(lake grass beach,reed beach),artificial use forest land(poplar forest,willow forest),artificial production land(farmland,breeding pond)as the research object,and uses traditional chemical methods combined with Arc GIS geostatistical analysis,CP/MAS ¹³C-NMR technology,high-throughput sequencing and other modern technologies to study the organic carbon distribution characteristics of The Hongze River Lake junction area.Using the physical composition of soil organic carbon under type,chemical composition characteristics and microbial community structure characteristics,the relationship between the physical composition and chemical composition of organic carbon under different wetland cover/utilization type,microbial community structure and wetland vegetation cover/utilization type is analyzed,thus revealing the impact of different land cover/utilization types on soil organic carbon distribution and acc?mulation mechanism,and strengthening wetland ecology for rational development and utilization,restoration and protection of wetlands Carbon sequestration provides a theoretical basis.The main results of this paper are as follows:(1)The distribution characteristics of soil organic carbon in Hongze Lake area were significantly different and affected by soil physical and chemical properties.The soil organic carbon density of wetland 0-20 cm soil layer is between 1.26-5.21 kg/m²,reserves between3048.11-82772.5 t;Soil organic carbon density in 20-40 cm soil ranges from 0.51-3.41 kg/m²,reserves between 1931.28-60137 t,Soil organic carbon density cm soil layers ranged from 1.76to 8.11 kg/m²,reserves between 4979.39.11-142910.27 t.The highest density of soil organic carbon was poplar,The lowest is lake grass beach,The highest reserve is the breeding pond and the lowest is Reed beach.Soil organic carbon density and reserves of organic carbon decreased with the increase of depth.The range of soil organic carbon density is not different from that of wetland soil in the middle and lower reaches of Yangtze River in China.The physical and chemical factors of wetland in Hongze Lake confluence area are not different from those of external disturbance,There was no strong coefficient of variation.Path analysis showed that the highest comprehensive ranking of environmental factors on soil organic carbon in 0-20 cm soil layer was species n?mber,and the highest comprehensive ranking of soil organic carbon in 20-40cm soil layer was total nitrogen(TN).(2)After nearly 30 years of land type transformation,There were significant differences in organic carbon content in different types of plots.The soil total organic carbon content of poplars(10.22 g/kg),willow trees(10.05 g/kg)and farmland(9.65 g/kg)in 0-20 cm soil layer was significantly higher than that of other plots,soil total organic carbon content(4.64 g/kg)in reed beach was significantly lower than other plots.20-40 cm soil,g/kg 9.64%of total soil organic carbon in willow forest was the highest among the six plots,The total organic carbon content(3.97 g/kg)and Reed(3.04 g/kg)in farmland soil were significantly lower than those in other plots.And this suggests that while farmland increases soil organic carbon levels cm 0-20,However,soil organic carbon content decreased rapidly in soil cm 20-40,Organic carbon is cons?med quickly.The soil organic carbon content of large particle size in farmland is the highest,The content of organic carbon in small size soil was the lowest,It also shows that its organic carbon is not easy to hold.The soil organic carbon content in willow forest is relatively high in two layers and small size soil organic carbon content,It shows that willow forest has strong retention and protection to soil organic carbon.The correlation analysis revealed,0-20 cm soil 200-2?m The organic carbon content was positively correlated with the soil total organic carbon content(P<0.01),Soil of 20-40 cm soil<2?m and 200-2000?m The organic carbon content?m the particle size component was positively correlated with the soil total organic carbon content(P<0.01),This indicates that the main input sources of total organic carbon in different soil layers are inconsistent.(3)The NMR signal intensity distribution of soil total organic carbon in different land cover/use types in Hongze Lake wetland was not consistent.Compared with other wetland types,the proportion of soil total soil,200-2000?m particle size component carbon functional group and light carbon alkoxide carbon in artificial willow and poplar forests,artificial production land farmland were significantly higher than those in lake grass beach and Reed beach.The percentage of organic carbon content and h?mification degree of different particle size components were analyzed.It was found that with the decrease of soil particle size,the proportion of h?mification index increased,and the stability of soil organic carbon was higher.(4)different wetland cover/use types 0-20 cm?20-40cm soil layer,deformable bacteria phyl?m(Proteobacteria),Bacteroides(Acidobacteria)is the main dominant population of soil bacteria.The Shannon index of bacterial community in soil samples of 0-20 cm?20-40cm soil layer was the highest in Reed beach.Bacterial communities of lake grass beach and reed beach,soil bacterial communities of farmland and culture pond,and soil bacterial communities of willow and poplar cm?2040cm in soil samples of 0-20 soil layers were formed into one group.The cover/use types of different wetlands in Hongze Lake confluence area 0-20 cm?20-40cm the whole soil of soil layer,the particle size component,the Ascomycota and basidiomycetes(Basidiomycota)are the main dominant populations of soil fungi.The observed species?Chao1index of fungal community in soil samples of 0-20 cm soil layer is culture pond>farmland,lake grass beach>Reed beach,poplar forest>willow forest,The Shannon index of fungal community was culture pond>lake grass beach>Reed beach>farmland,poplar forest and willow forest.The clustering results of fungal samples in soil samples of 0-20 cm?20-40cm soil were high similarity OTU soil fungal communities in willow and poplar forests,Reed and lake grass beaches,culture ponds and farmland soil fungal communities.Analysis of microbial community structure and soil physical RDA chemical properties showed that,Soil organic carbon content is the main factor affecting bacterial community structure,Soil moisture content is the main factor affecting fungal community structure.The acid bacteria phyl?m(Acidobacteria)in bacteria and basidiomycetes(Basidiomycota)in fungi are greatly affected by the organic carbon distribution of particle size components in soil<2?m,2-63?m,63-200?m.The organic carbon content increased obviously in the artificial forest of Hongze Lake River and Lake intersection area in the past 30 years,but the species and diversity of microorganisms did not increase with the increase of organic carbon.The increased organic carbon only increases the n?mber of specific microbial phyla rather than the microbial phyla.