The Relationship Between Dissolved Organic Matter Composition And Microbial Community In Urban Green Residential Space Soil In Different Climate Zones

Compared with land use types such as cultivated land,forest land and grassland,urban green residential space has higher consistency of grass species and management methods under different climatic zones,which can effectively avoid the interference of plant types and management measures on soil properties,and thus provide convenience for the study of soil DOM molecular composition and bacterial community distribution characteristics and their relationship under climate gradient.Therefore,it is of great significance to study the environmental factors affecting the spatial distribution of DOM and bacteria in the green space of urban communities for the material transformation and energy flow of terrestrial soil ecosystems.In this study,54 urban green residential space soil samplings were selected as research objects.Three-dimensional fluorescence spectroscopy,Fourier transform cyclotron resonance mass spectrometry,and 16S r RNA sequencing were used to study the composition and distribution characteristics of DOM and bacterial community in green space soil of urban communities distributed in typical climate areas.In order to clarify the species and DOM composition of soil bacteria in different climate zones,and quantify the contribution of environmental factors,so as to provide a scientific basis for further understanding of the influence of microorganisms on soil quality and maintaining soil stability.The main conclusions of this study are as follows:（1）In this study,five fluorescence components were identified in 54 soil samples,among which C1 was tryptophan mainly existing in the extracts of large plants,C2 was humic acid widely existing in the extracts of soil and biochar,C3 was a high molecular weight UVC humic acid component,C4 was a low molecular weight UVA humic acid component.C5 is a tryptophan similar to an amino acid,a complete protein,or a less degraded peptide.The proportion of C1 and C5 tryptophan in Tro M was the highest,the content of C2 and C3 in tropical monsoon climate region（Tro M）was not different,and the proportion of C4 in Tro M was smaller than that in other climate zones.In addition,HIX and SUVA₂₅₄ were the lowest in the subtropical monsoon climate region（Sub M）,while FI and S_R were the lowest in Tro M.In arid,semi-arid and semi-arid/sub-humid regions,the increase of precipitation leads to the increase of soil DOM humus.However,in humid areas,higher precipitation results in a lower degree of soil DOM humus.（2）In this study,there were significant differences in the spatial distribution of DOM at the molecular level,and mean annual precipitation and mean annual temperature were two key environmental variables controlling the chemical composition and diversity of soil DOM.The increase of precipitation can promote the accumulation of lipids and tannins,and consume the lignins and proteins in the environment.Increasing temperature can promote lipids accumulation and deplete phenols and aromatic hydrocarbons in the environment.（3）The bacterial community in this study was mainly composed of 42 phyla（including641 genera）.The bacterial community had no obvious regularity in the large-scale geographical pattern.However,the diversity and richness of bacteria in different climate zones are different,and there is a significant correlation with the chemical characteristics of DOM.In the bacterial community,the abundance of dominant phyla Proteobacteria and Actinobacteria decreased significantly with the input of proteins,while Chloroflexi increased significantly with the input of lignins.This study systematically analyzed the physical and chemical properties,DOM chemical characteristics and bacterial community composition of the green soils in 54 urban communities distributed in five typical climate zones,revealed the spatial variation rules of soil physical and chemical indexes,DOM and bacterial community structure,and identified the contribution of soil DOM to the terrestrial biogeochemical cycle in large-scale regions.This study provided a reference for the study of soil health and soil carbon dynamics under large-scale geographical pattern.