Analysis Of Four Common Tree's Pollen Dispersion Regulation And Allergenic Potential Evaluation In Beijing

Green space is an important part of the urban ecosystem.Among them,large amounts of allergenic pollen floating in the air can cause hay fever,which is a serious hazard to human health.This thesis selects the green space on the campus of Beijing Forestry University as the research object,and mainly conducts the following three aspects of research:(1)Four kinds of plants such as Forsythia suspensa,Cercis chinensis Bunge,Fraxinus pennsylvanica,Ailanthus altissima were selected for pollen monitoring,and the variation characteristics of pollen quantity at the breast diameter of allergenic plants were taken as the starting point to determine the daily variation of pollen dispersion during the time period of 6: 00-22: 00.Regularly analyze the influence of environmental factors(air temperature,relative air humidity,atmospheric pressure,radiance,wind direction,wind speed)on pollen dispersion,and clarify the relationship between pollen dispersion and environmental factors.Research indicates:(1)The pollen dispersion law of the four kinds of trees showed a "single peak" diurnal dynamic.From 6:00 to 22:00,the highest value of pollen quantity appears at 14:00 or 16:00,and the lowest value appears at 6:00 or 20:00.The peak-to-valley ratios of pollen quantity of Forsythia suspensa,Cercis chinensis Bunge,and Fraxinus pennsylvanica are smaller,and the peak-to-valley ratios of pollen quantity of Ailanthus altissima are larger.(2)The change in pollen quantity is the result of the combined action of many environmental factors.The pollen quantity is positively correlated with air temperature,irradiance and wind speed,and negatively correlated with air relative humidity and atmospheric pressure.Among them,the amount of pollen has a strong correlation with air temperature and relative humidity;it has a strong correlation with wind speed;the correlation with atmospheric pressure is inferior to air temperature,relative humidity and wind speed,and the correlation with radiance weak.At the same time,the amount of pollen is slightly more in the downwind direction than in the upwind direction.(3)Different environmental factors are independent of each other and have different effects on pollen quantity of different plants.The amount of Forsythia suspensa pollen is mainly related to the air relative humidity and wind speed factors,and the amount of pollen of Cercis chinensis Bunge,Fraxinus pennsylvanica and Ailanthus altissima is mainly related to the air relative temperature factor.(2)Based on the Gaussian formula,the urban green zone allergenicity index(IUGZA)is analyzed and improved(I'UGZA).The index is used to evaluate the allergenic potential of green space,and the allergenic potential of different regions is compared,the practical application of the index in estimating the allergenic potential of green space was explored.At the same time,Spearman correlation analysis and principal component analysis(PCA)were used to analyze the correlation between IUGZA and other parameters(surface area,number of plant,density,species richness,and Shannon-wiener index(H ')).Research indicates:(1)The overall IUGZA value of green space was 0.2141,and the I'UGZA value was 0.2193.It has hypoallergenic potential,and the pollen of plants growing in the study area does not pose a high risk to patients with pollen allergy.However,when the study area was compared,the IUGZA value of some areas was greater than 0.3,which had high allergenic potential.At the same time,allergic symptoms of allergenic people can be caused within 346 m range of allergenic plants.The I'UGZA value at 1000 m from the center of the field source approached 0,and there was almost no allergenicity.Therefore,the improved index can reflect the allergenic potential from different locations in the green space and the allergenic effect on the surrounding environment.It is an effective tool for assessing the allergenic potential of urban green space and is used to quantify the formation of pollen emissions in the air in different regions of the green space.(2)Highly allergenicity plants are Pinus tabuliformis,Quercus variabilis,Fraxinus pennsylvanica,Populus tomentosa,Ailanthus altissima,Ulmus pumila,Juniperus chinensis,Betula platyphylla and other plants in the study area,mainly belonging to Cupressaceae,Pinaceae,Salicaceae,Platanaceae,Leguminosae,Simaroubaceae,Ulmaceae,Betulaceae,and Fagaceae.There are many low allergenicity plants plants in green space,accounting for 65.7 %.Therefore,the index can reflect the contribution of pollen produced by each plant in green space,and then identify plants with high allergenicity in urban green space.(3)The results of principal component analysis(PCA)analysis are consistent with those of Spearman correlation analysis.There is a significant correlation between IUGZA and species richness(p<0.05),and the correlation with other parameters is not significant.Therefore,the index can also be used as a tool to analyze the richness of plant species in green areas.(3)From 2019 to 2020,phenology was used to observe and record the flowering period of all flowering plants in the study area,analyze the species composition and phenology of allergenic plants,and formulate a timetable for flowering plant pollen.Research indicates:(1)The allergenicity plants in the study area are mainly deciduous trees,accounting for 84.83%.(2)There are many flowering species in spring from March to May,mainly Populus,Cupressus funebris,Salix,Fraxinus chinensis and other allergenicity arbor plants.This period is the high incidence period of hay fever in the study area;July and August Mainly herb plants with few flowering species;no plants bloom from November to January of the following year.(3)The established pollen scattering schedule can clearly understand the plant types with large pollen amount in each month,so as to take corresponding protective measures.Based on the above research results,reasonable suggestions were proposed for the management and maintenance of green space.