| With the acceleration of urbanization in China,the urban environmental pollution problems are becoming more and more serious,and improving the urban ecological environment has become one of the hot issues concerned by the government and the public.As one of the important components of urban ecosystem,urban parks are known as the"lungs of the city"with the functions of regulating urban microclimate,purifying air and relieving pressure,providing people with comfortable leisure and recreation places and playing an important role in recreation and health care.Previous studies have mainly focused on the construction of functional areas in parks,ignoring the role of plant communities in park green areas for healing and health care.In recent years,the recreation function of urban forests has received more attention.However,the experimental monitoring of recreation function in parks is mostly in the form of linear deployment within plant communities,which leads to the temporal and spatial heterogeneity of recreation factors in plant communities have not been fully demonstrated.In this study,different modes of plant communities in three typical urban parks in Tai’an were selected as research objects to analyze the dynamic change patterns of air particulate matter(TSP,PM10,PM2.5,PM1)concentrations,positive and negative air ion concentrations,microclimate factors（temperature,humidity,wind speed）.In addition,this study explores the spatial and temporal variation characteristics and patterns of the main health factors in different plant communities based on geostatistics and ecological theories.The main findings are listed below:1.Spatial and temporal variation of negative air ion concentrationThe temporal and spatial variation of negative air ion concentration in various vegetation configuration modes have significant differences in the plant communities of the park（p<0.05）:summer>autumn>spring>winter,the highest average value of summer concentration reached1500/cm~3,the daily variation is manifested as"single peak"trend,the maximum value appeared during 10:00-14:00,the minimum value appeared during12:00-14:00.,According to the evaluation criteria,the"cleaner"standard is achieved and maintained for the longest time in summer.In spring and autumn,each configuration achieves’fair’and above.The spatial distribution of negative air ions varies considerably.In summer and autumn,the concentration of negative air ions in mixed coniferous forests is higher than that of pure forests,and the concentration was higher closer to the forest center;in spring and winter,pure coniferous forests,the concentration of negative oxygen ions in pure coniferous forests is higher than that in broad-leaved forests,and the concentration of negative oxygen ions was lower closer to the center.2.Pattern of spatial and temporal distribution variation of microclimateThe seasonal variations in temperature and relative humidity are significantly different（p<0.05）:summer>spring>autumn>winter;wind speed is prominently greater in spring than in other seasons（p<0.05）;the daily variation of temperature in plant communities within different configuration modes was unimodal,with a peak at 12:00-14:00;the daily variation of air relative humidity was trough-like,with the lowest value at 12:00-14:00.The seasonal variation of comfort level is manifested as:winter>spring>summer>autumn.The comfort degree in autumn basically reached“comfort level”and above while the comfort degree of human body in winter was above 6.95,marked as"extremely uncomfortable".The comfort index shows an unimodal trend in spring and winter,reaching the“comfortable”standard between 12:00 and 14:00.In contrast with the situation in summer.the results in autumn mostly achieve the“comfortable”standard,and all the results in winter reach the"uncomfortable"standard during the monitoring period,which indicates that it is not suitable for travelling and recreation in winter.3.Temporal and spatial variation patternMass concentrations of TSP,PM10,PM2.5 and PM1 are similar in seasonal changes,which is manifested as winter>autumn>spring>summer(TSP:90-350μg/m~3,PM2.5:15-70μg/m~3,PM1:10-20μg/m~3).In the daily changes,concentrations of air particulate matter mainly show"valley"pattern,high in the morning and evening and low at noon.Except for winter,particulate matter concentrations basically reached the"medium"standard.In summer,except for pure coniferous forests,concentrations of TSP and PM10 of other forests reached the"clean"level of ambient air,which is suitable for recreational travel.In autumn,concentration of TSP reached the"clean"level.In autumn,the concentrations TSP reached the"clean"level,which is suitable for recreational activities.Among the configuration patterns,the spatial variability is more obvious in summer,with the concentration of particulate matter low in center and high all around in the mixed coniferous forest,whereas in spring,the concentration is low in the pure coniferous forest and high at the forest edge.4.Overall discussion on health care factor and corresponding recommendationsCombined with the principal component analysis,the overall scores of the health care factors in various fields were ranked and manifest that:mixed P.Celtis sinensis-P.tabulaeformis forest,mixed P.Celtis sinensis-F.chinensis-C.deodara forest,and mixed P.tabulaeformis-R.pseudoacacia-Q.acutissima forests,have good effects,which provide suitable places for health care activities.In summer,the overall score of the health factor is the highest,which indicates that each forest stand is in the best recreation period during the whole monitoring period in summer;in spring,the results of all forest stands have reached the level III standard for recreation during the whole monitoring period;in autumn,the results have achieved the level II standard for best recreation at 8:00-12:00;the overall score in winter is the lowest among the four seasons.It is advised to avoiding health care activities in broad-leaved mixed forest at 8:00-10:00 as well as in the rest of the forest stands at 16:00-18:00.According to the redundancy analysis,it shows that the community structure characteristics had a strong effect on the health factor,and the richness,uniformity and diversity are negatively correlated with TSP,PM10 and cleanliness.In summary,the above research will affect the health maintenance effect of plant communities by exploring the temporal and spatial changes of urban park green space health factors and the changes of different vegetation configuration patterns.It provides a basis for the transformation and development of urban parks,and enriches the function and evaluation of urban green space ecosystem services. |
