Study On Pollen Sensitization Stress And Dispersal Rule Of Tree Layer In Comprehensive Park Under The Background Of Park City

Comprehensive parks are an important part of urban green space,an important green vehicle for interaction between citizens and the environment,safeguarding their health and biodiversity.Park city development brings opportunities for urban green space construction,and in the face of the proliferation of urban greenery,green space quality and safety are highly valued;however,some garden trees can release allergenic spores(spores and pollen),causing residents to suffer from allergic diseases(including allergic asthma,allergic rhinitis and allergic dermatitis),which seriously threaten human health.Most current research on park green spaces focuses on the aesthetic or ecological benefits created by plants,but little research has been conducted on the risk of plant spore pollen sensitization.This study takes People’s Park in Chengdu as an example and is divided into five main parts as follows.(1)Treading and calculating the species composition of trees and their diversity indices(including Margalef richness index R,Simpson diversity index D,Shannon-Wiener diversity index H and Pielou evenness index J)in eight different functional areas within People’s Park,The study showed that there were 1724 trees in the Park,belonging to 50 species,44genera,32 families.The most frequent trees were Lauraceae(17.03%),Pinaceae(14.35%)and Moraceae(9.21%),the level of species diversity in the tree layer of People’s Park is high,but the species evenness is medium,and there is still room to improve the plant species ratio and its ecological stability.There is still room for improvement.(2)Iugza,an allergenic risk index for urban green spaces,was calculated to investigate the influence of park landscape arbor characteristics on induced spore pollen allergenic risk.The results showed that the percentage of highly allergenic plant species in People’s Park was 38.89%,and the Iugza value was 0.696,which belonged to green areas with high sporopollen allergenic risk,where the most contributing allergenic species were ginkgo,balsam fir and cedar.(3)From March 12,2021 to February 25,2022,the palynology of plants in The People’s Park was collected by gravity sedimentation method,and species identification and concentration calculation were carried out,with a total of 625 exposed slides.The results showed that a total of 36171 pollen grains were collected.The seasonal dynamic distribution characteristics of sporopollen concentration are bimodal,which is the peak of spring and autumn respectively.The first peak of sporopollen concentration occurs in March and April,and the monthly average sporopollen concentration is 456.52 grains/1000mm~2and 116.70grains/1000mm~2,accounting for 62.57%of the annual sporopollen content.The spore-pollen species are mainly Indus,Salicylidae,Ginkgo and Pinaceae.The secondary peak occurred in September,and the average pollen concentration was 107.25 grains/1000mm~2,accounting for 11.71%of the annual pollen content.The main dispersal species were Pinaceae and Rhinocerotidae.(4)By comparing the measured sporopollen data of each region in the People’s Park with the results of the corresponding formula for calculating the sensitization index of the city,it was found that the formula had some limitations and did not consider the seasonal variation factors affecting the sporopollen dispersal,the actual distribution range of sporopollen dispersal,the interference of other air emissions and the influence of the cross-reaction between the sporopollen.(5)Correlation analysis of the sporopollen content of each area of People’s Park in four seasons with the corresponding meteorological factors showed that the order of correlation strength was temperature>light intensity>wind speed>relative humidity.In spring,summer and autumn,sporopollen concentration in the park was the highest in the range of18-23℃and increased with the increase of temperature,and when it was less than 18℃or more than 23℃,sporopollen concentration showed a negative correlation with temperature.In winter,the sporopollen concentration showed positive correlation with temperature in the interval of 0-15℃.In the light intensity range of 150-200 W/m~2,sporopollen content was higher and some areas showed a positive correlation between them in autumn.The wind speed in People’s Park was lower.Although the wind speed in the park was very small and did not change significantly throughout the year,a positive correlation between sporopollen concentration and wind speed was still found in some areas under weak wind conditions.Relative humidity showed a parabolic relationship with the change of sporopollen concentration,when the value was in the range of 50-60%,the sporopollen concentration increased with it,and when it was lower than 50%or higher than 60%,the two showed a negative correlation.(6)Based on the study of the plant composition of People’s Park and the measurement of plant spore powder,the study proposes a"three-step approach"to optimize spore powder sensitization from three aspects:source blocking,transmission barrier and predictive prevention and control,aiming to build a comprehensive urban hypoallergenic park integrating ecological safety,healthy recreation,leisure and entertainment,and scientific wisdom.The aim is to provide effective suggestions for the construction of a comprehensive urban hypoallergenic park integrating ecological safety,health recreation,recreation and science wisdom.