Spatial Heterogeneity Evaluation Of Uran Forest Ecosystem Services And Urban Forests In Urban Areas Of Zhengzhou City

As urbanization accelerates,the service function of urban ecosystem is decreasing,which leads to a series of ecological and environmental problems.Urban forestry is an effective,sustainable and economical means to improve the urban environment.Therefore,understanding urban forest ecosystem services and their spatial distribution is not only essential for urban planners and managers to effectively manage cities,but also an essential part of sustainable urban development.Assessing urban forest ecosystem services,mapping their spatial distribution,and improving the accuracy of their assessment scales will undoubtedly provide a more accurate reference for later management.In this study,240 sample squares were selected within the urban area using a grid randomization method,and each woody plant within the sample squares was checked for each wood size,taking Zhengzhou,a downstream city along the Yellow River in Henan Province,as an example.The i-Tree Eco model was used to analyze the structural characteristics of urban forest in Zhengzhou city based on field research data,and to estimate the ecological service functions of urban forest.Further,the spatial distribution of ecosystem services in the study area was mapped based on geostatistical principles,the mapping errors and applicable conditions were analyzed,and the main factors influencing the spatial heterogeneity of ecosystem services were further explored.The results of the study show that:（1）The structural characteristics of urban forest in Zhengzhou city using i-Tree Eco model found that tree species such as Broussonetia papyrifera,Celtis sinensis and Juglans regia occurred more frequently,White poplar was the tree species with the largest leaf area and leaf biomass,and the top five species with the highest importance values The top five tree species with the highest importance values were all deciduous broadleaf trees.The average diameter at breast height of trees was 13.26 cm,the average crown width was 3.95 m,and the average height was 5.93 m.（2）The i-Tree Eco model estimation results showed that the total carbon storage of urban forest in Zhengzhou city was 75.7t,the annual carbon sequestration was 14.66t/year,the trees and shrubs in Zhengzhou city could effectively avoid a total of 307.86m3/year of surface runoff,and the trees and shrubs removed air pollution(O₃,CO,NO₂,PM_2.5,PM₁₀and SO₂)411.8kg/year and a total of 38.3t/year of oxygen production.The spatial distribution of all indicators of urban forest ecosystem services was significantly heterogeneous,and all showed the highest values in the southwestern part of the study area and the lowest values in the southeastern part.The spatial analysis based on geostatistical principles showed differences in errors when used for the four indicators of carbon storage,carbon sequestration,surface runoff avoidance and pollution removal,which were related to the ecological processes of the evaluated indicators themselves.Carbon storage and carbon sequestration showed strong spatial autocorrelation,while surface runoff avoidance and pollution removal showed only moderate spatial autocorrelation.（3）The main influencing factors of spatial heterogeneity of ecosystem services were analyzed using geographic probes.The results showed that urban construction areas with high GDP and population density showed negative correlations with ecosystem services,while the highest ecosystem services were found in areas with combined forest and water.This study assessed urban forest ecosystem services and their spatial variation in urban areas of Zhengzhou City,Henan Province,and used a geodetector model to determine the factors influencing their spatial variation.The study shows that the spatial heterogeneity of various ecosystem services in Zhengzhou urban forest is obvious,urban construction is the main negative factor,and forest-water integration is an efficient way to improve ecosystem services.The coordination of land use conflicts and scientific construction for low value areas of ecosystem services are the focus of future work.This paper is a useful attempt to further explore the i-Tree Eco model and kriging interpolation based on the previous research,which is a useful attempt to study the urban forest space.Since Zhengzhou is the core of the Central Plains City Cluster in China and the core of the forest city cluster in Henan Province,this study not only helps Zhengzhou’s own urban forest development,but also provides a basis for the future urban forest construction and management in other cities,the Central Plains City Cluster and even the surrounding larger regions.This will contribute to the good performance of ecosystem services and thus improve the ecological and environmental conditions of the region.