Effects Of Vegetation Types On Soil Organisms’ Community And Functional Traits In Urban-suburban Park Green Spaces

Many ecological functions provided by soil are carried out by soil biodiversity.However,the process of urbanization has exerted a serious impact on the natural and agricultural ecosystem.The rapid expansion of urban areas has drastically reshaped the above-ground vegetation structure and has had a profound impact on the soil ecosystem,posing a serious threat to soil biodiversity.At present,the impact of urbanization and vegetation types on soil biodiversity and its functional traits and the mechanisms underlying these differences remain largely unknown.In this thesis,amplicon sequencing technology was used to analyze the diversity of soil biota,including bacteria,fungi,protists,nematodes,meso-and macrofauna.At the same time,to better understand the functional changes of soil biota under environmental disturbance,the community and functional traits of Collembola,a representative group of soil mesofauna,were determined by traditional methods of isolation and identification of soil animals.To explore the effects of urbanization(urban-suburban)and vegetation types(forest-park: grassland,grassland + shrub,grassland + tree and grassland + shrub + tree)on soil organisms’ community and functional traits.The main results were as follows:(1)The effects of urbanization and vegetation types on soil biodiversity(based on high-throughput amplicon sequencing technology)In terms of soil organism alpha diversity,the responses of soil organisms to urbanization levels and vegetation types among groups.Soil fungal species richness was closely related to vegetation types,and the diversity increased with the complexity of vegetation.However,bacteria,protists,nematodes,meso-and macrofauna and soil multidiversity did not respond significantly to the differences of vegetation types in the park.The richness of protists and meso/macrofauna was affected by urbanization and was positively associated with soil nutrient levels,and their richness in urban was significantly higher than that in suburban.The bacterial community showed the opposite trend,its richness in suburban was slightly higher than that in urban,and was negatively correlated with soil nutrient levels.The richness of nematodes was also affected by urbanization,but the direction of influence depended on vegetation type.Compared with other vegetation types in the park green space,soil biodiversity was higher in the habitat of the most complex vegetation type(grassland + shrub + tree),indicating that this habitat may have greater potential for soil biodiversity conservation in urban ecosystems.In terms of soil biota community composition,vegetation type had a strong effect on community composition for all soil biotas.Based on amplicon sequencing results,all soil biotas community compositions were strongly driven by vegetation type.Vegetation complexity promoted the stability of soil communities,that is,in grassland+ shrub + tree habitat,soil community composition has the least variation among sites and the community is the most stable.In addition,fungal community composition was most tightly connected to all other soil biotas,suggesting that they play an integral role in urban ecosystems.(2)The effects of urbanization and vegetation types on the community and functional traits of Collembola(based on the methods of isolation and identification of soil animals)In terms of soil Collembola diversity and community composition,urbanization and green space type had certain effects on soil Collembola abundance,species richness and diversity.They were higher in suburban than in urban,and forests are higher than park green spaces.The results of structural equation modeling showed that the negative effects of urbanization and park green space on Collembola richness may be partly caused by both soil physicochemical properties and soil bacterial diversity.In addition,soil Collembola community composition was driven by vegetation types.In terms of functional traits and functional diversity of soil Collembola,the composition of soil Collembola functional traits and functional diversity had obvious responses to the urbanization and green space types.Compared with the forest,the collembola community in the park green space is dominated by epedaphic species with pigmentation,more developed furca and ocelli,and fast dispersal.Furthermore,the composition of functional traits of the soil Collembola community was driven by soil fungal diversity.