Characterization Of Soil Microbial Communities And Influencing Factors Of Two Classic Urban Riverside Ecological Corridors In Shanghai

Along with the accelerating process of urbanization,and the alteration to the land use has become an irreversible trend,and there is no doubt that human bring the the impact on urban ecosystems is.In order to protect the biodiversity of urban ecosystems and enhance urban landscapes,many megacities have designed ecological corridors to establish the urban natural landscape frameworks,which are bound to fragmented green space patches,conducive to the energy and matters transfer between patches,can maintain species diversity,and profoundly influence and enrich the spiritual and cultural experiences of people,and the riverine ecological corridors are one of the important forms.City of Shanghai contains the dense river network,which contributes to the richness of the riverfront ecological corridors within the city;likewise,the number of artificially constructed urban ecological corridors is numerous.The study of ecological corridors can better protect the ecological security and urban biodiversity of Shanghai and help to develop this city in a way of more ecologically.This project investigates urban riverine ecological corridors in Shanghai and compares the two most common types of riverine corridor structures（i.e.,concrete isolated corridors and soil non-isolated corridors）,and to analyze the effects of different structural properties of riverine ecological corridors on soil physicochemical properties,microbial structure,composition,diversity and their functions.The study showed that:（1）There are significant differences in soil physicochemical between different types of riparian ecological corridors.The variation of soil bulk weight at each point ranged from 0.18-0.61 g/cm3,the variation of water content ranged from 14%-290%,and the soil at all points showed alkalinity.By ANOVA,the soil non-barrier corridor significantly reduced soil bulk density,p H value,and increased soil water content.For soil nutrients,the variance of soil ammonia nitrogen,nitrate nitrogen,organic carbon and total nitrogen ranged from 0.02-78.01 mg/kg,0.92-17.45 mg/kg,0.51-14.26 g/kg and 3.56-228.79 g/kg,respectively,and the soil non-isolated corridor had higher soil organic carbon（SOC）and total nitrogen（TN）.For the spatial comparison of the same type of corridors.Soil water content decreases with increasing soil depth and offshore distance,while p H has the opposite trend of increasing,and soil nutrients such as SOC and TN are also significantly higher in surface soils than in deeper soils.In terms of offshore distance,soil corridor sites close to the water-land interface（20 cm,1 m）were richer in water content and nutrients such as carbon and nitrogen,while cement corridor sites were almost unaffected by offshore distance.（2）There were significant differences in bacterial community composition and structure between the two types of riparian ecological corridors.For example,at the phylum level,Proteobacteria were the most abundant bacterial phylum,and their abundance was higher in the non-barrier corridor（especially at points near the land-water interface）,while Actinobacteria and Acidobacteria were more abundant in the cement barrier corridor.PCo A and RDA analyses also showed significant differences in bacterial community structure between the two types of corridors,especially at the water point（20 cm）,which were mainly due to differences in soil The significant differences in the composition and structure of the two different types of corridor bacteria were mainly driven by the differences in water content and the content of carbon and nitrogen.（3）The diversity of bacterial communities between the two types of riparian ecological corridors did not show significant difference.Although the results of ANOVA on the four indices ofαdiversity of bacterial communities in the two types of corridors did not reach a significant level（p>0.05）,the soil non-isolated corridor was slightly higher than the concrete isolated corridor in terms of chao1 index,and overall,theαdiversity index of surface soil bacteria was higher than that of the subsurface soil.（4）Non-isolated soil corridors elevated soil carbon（processes such as 3-hydroxypropionic acid cycle,Calvin cycle,formaldehyde and methane conversion）,nitrogen（e.g.ammonia to hydroxyl ammonia（NH₃→NH₂OH,involving amo ABC genes）,nitrate and nitrite conversion（NO₂^-→NO₃^-,involving nxr AB,nar GHI,nap AB,nar B,nr&nas AB genes）and other processes）,sulfur(DMSP demethylation（MMPA→Me SH,involving dmd BCD or acu H genes）,sulfide oxidation（sulfide→sulfur,involving fcc AB genes）,hydrogen sulfide and sulfite conversion(H₂S→SO₃^2-,etc.involving dsr AB genes)and other processes),and other biological geochemical cycling processes.In addition to the carbon,nitrogen,and sulfur cycling,others such as the isomerized arsenic reduction process,cytochrome bd ubiquinone metabolism process,and diarginine synthesis process,the gene abundance of these pathways were higher in the non-barrier corridor than in the barrier corridor.Therefore,these results suggest that soil non-isolated ecological corridors should be considered as the main approach in Shanghai,which will be beneficial to the conservation of soil biodiversity and the maintenance of ecosystem functions.