Coupling Relationship Between Urban Forest Health-care Factors And Leisure Physical Activity In Xi’an Metropolitan Area

Cities are the basis for the survival of modern human society.However,urban problems such as air pollution and urban heat island seriously threaten the physical and mental health of residents.Urban forests have attracted much attention due to their functions of improving air environment and promoting human health.This study is based on the lack of research on the spatial and temporal association between urban forest health-care factors and residents’recreational and physical activities using their health-care functions.In this study,nine typical urban forests（urban parks）in different areas（urban core area,transitional area,and peripheral area）of three cities（large-scale city-Xi’an,medium-scale city-Baoji,and small-scale city-Yangling district,they are all in the Xi’an metropolitan area）with rich urban forest resources were selected as the study area.Based on the urban forest survey and the actual measurement of the main health-care factor indicators,this study conducts a research on the temporal and spatial changes and coupling relationship between urban forest health-care factors and residents’leisure physical activities.It elucidates the association between the main health-care factors and residents’leisure physical activities in urban forests at different temporal and spatial scales.It provides a theoretical basis and practical basis for guiding urban residents’leisure and physical activities and improving their health quality.The results of the study are as follows:（1）Based on different temporal and spatial scales of empirical measurements,we obtained the spatial and temporal variation patterns of the main health-care factors in the urban forest of Xi’an metropolitan area.The air negative ion（NAI）concentration in the urban forest forest varied significantly seasonally,with the highest in summer（average 799/cm³）,followed by autumn（560/cm³）and spring（544/cm³）,and the lowest in winter（329/cm³）.There was a clear pattern of daily variation in the air negative ion concentration in the forest,with an overall trend of single-valley variation.The decreasing period was from 8:00 a.m.to 12:00 p.m.,the lowest value was at 13:00 p.m.,and the increasing period was from 14:00 p.m.to 17:00 p.m.The concentration of negative air ions in the urban forest varied significantly spatially,with the highest concentration in medium-sized cities（average 648 ions/cm³）,followed by small-sized cities（550 ions/cm³）,and the lowest in large-scale cities（476 ions/cm³）,with the highest concentration in urban fringe areas,followed by urban transition areas,and the lowest in urban core areas.The seasonal variation of PM_2.5concentrations within the urban forest stands was significant,with the highest in winter（mean 106.2μg/m³）,followed by spring（42.0μg/m³）and autumn（34.1μg/m³）,and the lowest in summer（21.0μg/m³）.The daily variation of PM_2.5concentration in the forest showed the same performance in spring,summer and autumn,all showing a slow increasing trend.The in-forest PM_2.5concentrations in winter behaved differently depending on the city scale and the location of the forest in the city.In large and medium-sized cities,PM_2.5concentrations showed a single-peak trend in winter.The rising period is from 8:00 a.m.to 14:00 a.m.,reaching the highest value throughout the day by 14:00a.m.,and the decreasing period is from 14:00 p.m.to 17:00 p.m.In small-scale cities,PM_2.5concentrations are increasing during 8:00-17:00 in winter.PM_2.5concentrations within the urban forest forest varied significantly spatially,with the highest concentrations in large-scale cities（average 57.5μg/m³）,followed by small-scale cities（49.1μg/m³）,and the lowest in medium-scale cities（45.8μg/m³）,with the highest in the urban core,the second highest in the transition zone,and the lowest in the periphery.The Urban Forest Thermal Universal Climate Index（UTCI）has significant seasonal variations,with the highest in summer（average 31.2°C）,the second highest in spring（21.2°C）,the third lowest in autumn（15.9°C）,and the lowest in winter（6.2°C）.The thermal general climate index has a clear pattern of daily variation with an overall trend of single-peaked variation.The rising period was from 8:00 a.m.to 12:00 p.m.,the highest value for the whole day was at 13:00 p.m.,and the falling period was from 14:00 p.m.to 17:00 p.m.The thermal generic climate index within the urban forest forest varied significantly spatially,with the highest in large-scale cities（19.9°C on average）,the second highest in medium-scale cities（19.5°C）,and the lowest in small-scale cities（16.4°C）,with the highest in the urban core,the second highest in the transition zone,and the lowest in the peripheral zone.In terms of the relationship between the main health-care factors within the urban forest stands,PM_2.5concentration was significantly negatively correlated with air negative ion concentration.The thermal generic climate index was significantly negatively correlated with negative air ion concentration.The thermal generic climate index was positively correlated with PM_2.5concentration.（2）Based on different temporal and spatial scales of empirical measurements,we obtained the spatio-temporal variation patterns of urban forest leisure physical activity（LPA）in the Xi’an metropolitan area.The cumulative number of participants in leisure physical activities in urban forests was higher for women（55.56%）than for men（44.43%）.The larger the size of the city the smaller the gender difference in participation in leisure physical activity.Adults（44.91%）and the elderly（38.92%）were the main groups of people who engaged in leisure physical activities.Among the total population,the largest proportion of people engaged in moderate intensity leisure physical activity（30.7%）,followed by low intensity（27.5%）,followed by static activity（21.3%）and the least high intensity activity（20.5%）.The larger the city size the higher the proportion of people performing static activities,and the proportion of people performing high-intensity leisure physical activities is higher in spring,summer and autumn than in winter.Outdoor sports activity areas（47.5%）and central squares（32.8%）are the main spatial places for leisure physical activities in the urban forest environment.The seasonal variation of the cumulative number of leisure physical activity in the urban forest is obvious,from high to low in spring,autumn,summer and winter.Leisure physical activities were mainly conducted during the hours of 9:00-10:00 am and 15:00-16:00 pm.The larger the size of the city where the urban forest is located,the higher the cumulative number of leisure physical activity visits,with the highest in large scale cities（75.76%）,the second highest in medium scale cities（15.24%）,and the lowest in small scale cities（9.00%）.The closer to the urban core,the higher the cumulative number of leisure and physical activity visits.（3）The correlation between the main health-care factors of urban forests and the leisure physical activities of residents in the Xi’an metropolitan area was elucidated.There was a strong correlation between negative air ion concentration and leisure physical activity in urban forests（correlation r_i=0.685）,with the highest correlation among seasons in summer（0.736）,followed by autumn（0.713）and spring（0.675）,and the lowest correlation in winter（0.617）.There was a strong correlation between PM_2.5concentration and leisure physical activity in the forest（correlation r_i=0.657）,with the highest correlation among seasons in winter（0.803）,followed by spring（0.650）and autumn（0.632）,and the lowest in summer（0.544）.The thermal generic climate index in the forest had a weak correlation with leisure physical activity（correlation r_i=0.630）,with the highest correlation among the seasons in winter（0.763）,followed by spring（0.628）and autumn（0.572）,and the lowest in summer（0.556）.Based on the assessment of the correlation and rationality between the main health-care factors of urban forest and residents’leisure physical activities,it is suggested that the thermal generic climate index is the main reference index for urban residents’leisure physical activities plan in summer,the negative air oxygen ion concentration is the main reference index in spring and autumn,and the PM_2.5concentration is the main reference index in winter.