Study On The Response Of Three Evergreen Shrubs To Major Pollutants And Assessment Of Air Pollution Tolerance And Prediction Of Anticipated Performance Of Commonly Used Woody Plants In Landscape

As urbanization and industrialization accelerate,the main air pollutants（PM2.5,PM10,SO₂,NO₂,O₃ and CO）have become important factors affecting the urban living environment and human health.In the process of urban ecological and environmental engineering,commonly used woody plants with high air pollution tolerance and anticipated performance capacity can improve the ecological quality of cities and people’s living environment.This paper firstly investigates the morphological,physiological and biochemical responses and air pollution tolerance of three commonly used evergreen shrubs in landscape in the field.Secondly,in order to explore further the differences and correlations between the atmospheric pollution tolerance of commonly used woody plants in landscape,the literature search was used to extract data on variables related to the Air Pollution Tolerance Index（APTI）for 100 woody plants commonly used in landscape,including chlorophyll content（TCH）,relative water content（RWC）,p H,ascorbic acid content（AA）.And calculated the values of APTI,then evaluated the air pollution tolerance capacity of 100 commonly used woody plants.Establish regression equation models for APTI and TCH,RWC,AA,p H,and the best fit was selected,and then the AA of three evergreen shrubs in the field study were substituted into the regression equation to verify the accuracy of the regression model.Finally,40 commonly used woody plants（three evergreen shrubs from the field study and 37 commonly used woody plants from the literature search）with medium and above air pollution tolerance were selected to predict their anticipated performance capacity,providing a reference for the selection of air pollution resistant woody plants for future landscaping.The main findings are as follows.（1）In the field study part,three typical evergreen shrubs in Shanghai were used as test materials,including Viburnum odoratissimum Ker.Gawl.（VO）,Rhododendron×pulchrum Sweet（RP）and Pittosporum tobira（PT）,Based on the air quality monitoring data released by the Shanghai Bureau of Ecology and Environment for the three years from 2020 to 2022,the Mann-Whitney rank sum test analysis was used to classify Qingpu District as a polluted area and Fengxian District as a relatively clean area.15 morphological,physiological and biochemical variables of the three shrubs in two zones were determined and analyzed,including the Leaf length（LL）,Leaf width（LW）,Leaf size（LS）,Midvein width（MW）,Petiole length（PL）,Chlorophyll a（CHLA）,Chlorophyll b（CHLB）,Soil and plant analyzer development（SPAD）,Leaf water saturation deficit（LWSD）,Soluble sugar content（SS）,Malondialdehyde content（MDA）,RWC,TCH,p H,AA.And the air pollution tolerance index（APTI）of the three shrubs was calculated by TCH,RWC,p H,and AA in order to assess the atmospheric pollution tolerance.The variability of these variables was analyzed by t-test,and it was found that all 15physiological and biochemical variables were susceptible to changes in atmospheric pollution and had different degrees of variability.Compared with Fengxian District,VO in Qingpu District showed significant decreases in LL,MW and p H,and significant increases in SPAD,AA and SS;RP in Qingpu District showed significant decreases in LL,LW,LS,p H,RWC,TCH,CHLA and CHLB,and significant increases in LWSD,AA,SS and MDA;PT in Qingpu District showed significant decreases in LL,p H and RWC,and significant increases in LW,LS,LWSD,CHLB,AA,SS,and MDA had significant increases.This shows that the three shrubs adapt to changes in atmospheric pollution by adjusting leaf morphology and structure,regulating chlorophyll content and activating antioxidant systems.By assessing the air pollution tolerance of the three shrubs,it was found that the three shrubs had a higher air pollution tolerance index in the more polluted（Qingpu area）,showing a medium air pollution tolerance.（2）In the literature search section,100 commonly used woody plants were selected through extensive reading of representative literature,and the data on TCH,RWC,p H and AA of woody plants were obtained.The air pollution tolerance capacity of 100 commonly used woody plants were assessed by calculating the air pollution tolerance index.63 commonly used woody plants that are sensitive to air pollution were assessed,including Jacaranda mimosifolia D.Don,Spathodea campanulata P.Beauv.and Bauhinia purpurea L.,which can be used as indicator plants to identify the level of air pollution.37 commonly used woody plants with medium and above tolerance to air pollution were assessed,including Ailanthus altissima,Ligustrun lucidum Ait and Cedrus deodara（Roxb.）G.Don,which can be used mostly for the greening of industrial areas and street greenery.The AA and APTI regression equations were found to have the best fit（R²=0.85）through regression analysis,and the fitted equation was:y=5.577291359393123+2.374817058188567*x-0.1238483261643137*x²+0.002524396998637555*x³,where x is the AA value of woody plants,and y is the APTI value of woody plants.The accuracy of this regression equation was also verified by the AA data of the three evergreen shrubs obtained from the field study.Therefore,the APTI of woody plants can be calculated directly by substituting the AA of that woody plants into the equation,and estimating the air pollution tolerance of the woody plants.It provided a convenient and efficient method for future air pollution tolerance assessment of woody plants in the landscape.（3）The results of air pollution tolerance analysis from field studies and literature screening were combined to select 40 woody plants with medium and above air pollution tolerance（3woody plants from field study and 37 woody plants from literature search）,and the anticipated performance index of these 40 woody plants were assessed by combining the air pollution tolerance index,ecological value and socio-economic value of woody plants to predict their anticipated performance capacity.At the level of air pollution tolerance of woody plants,the woody plants with the best anticipated performance capacity,such as the Mangifera indica,Ficus religiosa L.and Ficus bengalensis,were selected,and recommended for mass planting in their suitable areas.VO,PT and Aegle marmelos have average performance and can be selected appropriately.Woody plants such as RP,Hibiscus syriacus Linn.,and Moringa oleifera Lam.have the worst anticipated performance capacity and are not recommended for planting in large numbers in the landscape.