Leaf Functional Traits Of Common Tree Species And Their Response To The Environment In Shanghai

Urban areas are highly active ecosystems for human activities.With the rapid development of global urbanization,the urban environment is undergoing significant changes.Plant leaves are highly plastic and sensitive to the environment change,and their functional traits can reflect the adaptation strategies of plants to cope with environmental change,with important implications for vegetation characteristics and ecosystem function.Therefore,in the context of global change and intensified anthropogenic activities,analyzing leaf functional traits in urban greenery and their interrelationships with the urban environment will help to better understand and predict community structure dynamics and improve ecosystem services and functions.To explore the adaptation strategies of trees in the Shanghai green belt to the urban soil and atmospheric environment,we conducted a study in the area.We set up 62 sample plots(30 m * 30 m),measured soil nutrients and atmospheric pollutant concentrations,and examined the leaf functional traits of major woody plants in each plot.Then,an analysis was carried on the relationships between leaf functional traits and their associations with environmental factors.The aim of the study is to provide a scientific basis for the functional improvement of the Shanghai green belt and other urban greenery in the city.The main results are as follows:(1)The findings indicate that leaf area has negative correlations with leaf index,specific leaf area,leaf carbon content and leaf nitrogen content.Leaf index,on the other hand,demonstrates a significant positive correlation with leaf carbon content,and a negative correlation with leaf phosphorus content.Specific leaf area is positively correlated with leaf nitrogen content,leaf phosphorus content and leaf potassium content,but negatively correlated with leaf dry matter content and leaf carbon content.Additionally,leaf dry matter content shows a strong correlation with leaf nutrient content,which includes leaf carbon,leaf nitrogen,leaf phosphorus and leaf potassium content.And leaf dry matter content is positively correlated with leaf carbon content and negatively correlated with leaf nitrogen content,leaf phosphorus content and leaf potassium content.The correlation between leaf carbon content and leaf nitrogen,as well as leaf potassium content,is negative.Finally,leaf nitrogen content,leaf phosphorus content and leaf potassium content are positively correlated with each other.(2)The interrelationships between leaf economic traits were analyzed and compared between common green tree species in Shanghai and the global leaf trait database.The findings suggest that the leaf economic spectrum observed in Shanghai’s trees aligns with the global pattern.Specifically,evergreen plants were found to exhibit resource conservative characteristics with higher leaf mass per area,as well as lower leaf nitrogen and phosphorus content,placing them at the ’slow investment-reward’ end of the leaf economic spectrum.In contrast,deciduous plants were observed to be resource acquisition-oriented characteristics,such as lower leaf mass per area and higher leaf nitrogen and phosphorus content,and therefore fall on the ’fast investment-reward’ end of the leaf economic spectrum.It is worth noting that the trees in this study displayed a lower leaf mass per area and higher leaf nitrogen and phosphorus content when compared to the trees in the global leaf trait database.This is potentially explained by the city’s preference for using fast-growing tree species in its greenery planning.(3)The study aimed to investigate the relationships between soil nutrient conditions and atmospheric pollutant concentrations and tree leaf functional traits for nine widely distributed tree species.The study found that the effects of environmental factors on leaf functional traits varied between species,suggesting that each species may have its own unique response to environmental stressors.Overall,atmospheric pollutants were the dominant environmental factors affecting leaf index,specific leaf area and leaf carbon content.In contrast,soil nutrients were found to be the main environmental factors affecting leaf area and leaf potassium content.(4)Further variance partitioning analysis was performed for the above functional traits in relation to environmental factors,and it was found that among the 8 leaf functional traits,the leaf area,specific leaf area and leaf potassium content were more likely to respond to urban soil and atmospheric conditions.Among all the tree species,Ligustrum lucidum,Koelreuteria bipinnata and Fatsia japonica were more sensitive to urban soil and atmospheric conditions,while Cinnamomum camphora,Celtis sinensis and Trachycarpus fortune were less influenced by the environment factors.In conclusion,anthropogenic preferences and urban environmental factors are both important factors affecting the leaf functional traits of urban tree species in Shanghai.At the species level,the demand for fast-growing trees in urban greening has led to a predominance of ’fast investmentreward’ species,soil nutrient changes and atmospheric pollution from urban development are driving adaptation in leaf morphological structure and physiology in green trees.However,the study also found that each species may have its own unique response to environmental stressors.