Spatial Distribution Of Urban Soil Organic Carbon Density And Its Influencing Factors In Xi’an City

Soil organic carbon is an important component of the terrestrial carbon pool,and urban soils play an important role in the functional services of urban ecosystems,which are increasingly subject to anthropogenic impacts with the rapid expansion of urbanization.Rapid urbanization and continuous anthropogenic disturbances have caused land use types and urban landscapes to exhibit complex dynamic patterns,but how such complex dynamic patterns affect urban soil organic carbon pools is unclear.In this paper,213 soil sampling sites were set up within the Xi’an Bypass Highway to systematically analyze soil bulk weight,soil organic carbon content and microbial carbon,calculate urban soil organic carbon density and microbial entropy,and discuss the effects of land use type,population density,impervious surface,landscape pattern index and other urbanization characteristic indicators on soil organic carbon.The main results are as follows:（1）The results of statistical analysis showed that the mean soil bulk weight of urban soil in Xi’an was 1.38 Mg·m^-3,organic carbon content was 12.60 g·kg^-1,soil organic carbon density was 3.44 kg·m^-2,microbial carbon was 0.13 g·kg^-1,and soil microbial entropy was 1.11%,with coefficients of variation of 7.36%,49.78%,42.93%The coefficients of variation were7.36%,49.78%,42.93%,47.36%,and 38.60%,respectively.Soil organic carbon content,microbial carbon,organic carbon density and soil microbial entropy all have medium intensity variability.（2）The variability of the spatial distribution of soil organic carbon density in urban Xi’an is significant,and the areas near the urban center obviously have higher organic carbon density,and it decreases from the center to the outside.This spatial distribution pattern in Xi’an is due to differences in soil properties,land use types,built-up history and management practices and other related influences.（3）Land use type is the main influencing factor for the variation of soil organic carbon density.Soil organic carbon density in Xi’an differs significantly among different land use types,with soil organic carbon density in the order of parkland(3.85 kg·m^-2)>public land(3.82 kg·m^-2)>transportation land(3.65 kg·m^-2)>commercial land(3.50 kg·m^-2)>agricultural land(2 kg·m^-2)>community land(3.11 kg·m^-2)>industrial land(2.95 kg·m^-2)>unused land(2.35 kg·m^-2).It shows that in urban ecosystems,differences in the intensity of anthropogenic disturbances under different land use types directly affect soil organic carbon density.（4）Correlation analysis showed that changes in the urban landscape pattern index were the driving factors influencing changes in urban soil organic carbon in Xi’an.The landscape shape index,aggregation index and landscape fragmentation index were significantly correlated with organic carbon density.The fragmentation of landscape patches and the heterogeneity of patch types in Xi’an are high,and urban soils are seriously influenced by human factors directly or indirectly affecting the density of soil organic carbon.In addition,the percentage of landscape patch area of community land,public land,commercial land,and unused land also had significant correlation with organic carbon density.The results of principal component analysis showed that the landscape shape index was the largest principal component loading,followed by the aggregation index.Therefore,landscape shape index and aggregation index are important landscape pattern indicators affecting organic carbon distribution.（5）Urbanization factors in this study have positive effects on urban soil carbon pools.Population density,impervious surface,and road density have a significant positive correlation on soil organic carbon density.It indicates that urbanization has a positive effect on the accumulation of urban soil organic carbon.Translated with www.Deep L.com/Translator（free version）...