Structural Characteristics And Eco-environmental Service Functions Of Urban Forests

Whether the urban forests can fully utilize the functions of ecological environment services depends on the rational planning of artificial plant communities and the creation of excellent environmental quality.As an important part of urban forests,urban parks should match the community composition.Identifying the structural characteristics,leading functions and influencing factors of urban forests in urban parks will provide data support and theoretical basis for maximizing ecological service functions,optimizing and arranging urban parks,planning and building livable forest cities.This paper regarded the South Lake Park as the representative of the city forest in the city.The spatial structure characteristics of woody plants were analyzed.The carbon sink of woody plants was estimated to perform spatial characteristics of carbon fixation and oxygen release.Temperature and humidity data were collected and normalized to explore the influencing factors the role of urban forest in mitigating urban heat island effect and its influencing factors.Operational research method ANP was introduced to evaluate the comprehensive environmental quality of the South Lake Park and influencing factors was found.The results showed:(1)There were a total of 1421 woody plants in the study area,belonging to 22 families,47 genera and 67 species.There were1269 arbors among them and 152 clumps of shrubs.The number of species of woody plants in South Lake Park was reasonable,the geographical composition of the flora in the study area was complex and the ecosystem was stable.The overall age composition of the arbor showed a typical growth structure.The regeneration ability was strong and the community was relatively stable.The dominant populations were dominated by middle-aged forests and mature forests,and some populations showed a slight decline trend.The species richness of the patch internal community was slightly higher than that of the patch edge,and the diversity dominance was opposite.The further the community position was from the waterside,the more obvious the difference in species richness and diversity between communities,and the greater the species richness.The richness and diversity of the community increased slightly with the increase of conifer-broadleaf ratio and the ratio of shrub to arbor.(2)The samples with a carbon sequestration of more than50kg were less than 20%.The overall carbon sequestration and oxygen release capacity of the park was weak,indicating that the configurations of current woody plant community structure and forest age in the South Lake Park were unreasonable.The carbon sink capacity of the community were determined by the structure and age of the community,not the number of carbon sink plants.The maximum temperature drop was 4.28℃,the maximum humidification was 35%.The heat island mitigation effect of the community was obvious.Decreasing the conifer-broadleaf ratio enhanced the cooling effect,while the humidification effect decreased first and then increased.The high and low density of arbors would inhibit the cooling effect.The optimum density of arbors was 0.08 plants/m~2,and the humidification effect was weakened as the density of trees was reduced.The average value of the beauty was 5 and the standard deviation was 1.5.The degree of beauty scores gradually decreased from southwest to northeast,and the subjective feelings of tourists on the beauty of woody plant communities in the study area were moderate.The intensity of recreational activities was strong in the north and south,and weak in the central and western regions.Among the 7grades,the samples at the 4th and 5th grades accounted for 76%.The overall recreational intensity was moderate,and the middle-aged forest with appropriate shrubs was highly disturbed.(3)Based on vegetation quality,functional quality and aesthetic quality,ANP was used to construct an indicator system for landscape quality assessment within forests.The evaluation results showed that among the secondary indicators,the forest structure structure had the greatest impact on environmental quality,which was 27.6%;and the impact of forest aesthetics was the smallest,which can only explain the reasons for the 11.5%environmental quality change.At present,the overall community environment quality of the South Lake Park was poor.It is necessary to create better environmental quality from three aspects:vegetation quality,functional quality and aesthetic quality.