Study On The Characteristics Of Leaf Economic Spectrum Of Lingering Garden And Its Landscape Optimization Strategy

Plant leaves are the main place for the mutual conversion of matter and energy between plants and the external environment,and their external morphological and functional traits can show the basic functional characteristics of plants and the utilization efficiency of resources by plants to a certain extent.Leaf functional traits in plants establish universal associations between plant diversity,species composition and physiology,and environmental changes,and play an important role in explaining species distribution and species coexistence mechanisms.The leaf economic spectrum quantifies the changing laws and relationships among plant leaf functional traits,representing a series of interrelated and synergistic plant resource trade-off strategies at the leaf level.In recent years,the leaf economic spectrum of plants has attracted the attention of ecologists.The study of plant leaf functional traits and leaf economic spectrum in different regions and different ecosystem types has been applied and extended to many research fields.The discipline of landscape architecture is no exception,starting to focus on the multiple connections between plant leaf functional traits and urban garden green space systems.The latest research progress in the field of landscape architecture on"the adaptation mechanism of plants to the environment"mostly takes plant leaf traits as the starting point.Studying the leaf traits of garden plants can better reflect the responsiveness of individual plants and even urban garden ecosystems to the environment.In the construction of garden green space,the selection and rational allocation of garden plant species have an important impact on the health and stability of the garden ecosystem.As one of the four major classical gardens in China,the Lingering Garden is composed of rocks,water,buildings and plants to form a balanced"micro-ecosystem"of resource circulation and symbiosis.The configuration of plants in the garden focuses on the integration with the environment,and their life characteristics have the function of recording the development process of the garden and inheriting the historical features.This paper adopts the method of leaf economic spectrum theory to focus on the research on Lingering Garden.17 leaf economic spectrum（LES）traits including leaf thickness（LT）,specific leaf area（SLA）,leaf nitrogen concentration on mass basis(N_mass),photosynthetic capacity on mass basis(A_area),and transpiration rate（T_r）were selected for determination to analyze the changing laws of leaf economic spectrum characters of 36 plants in Lingering Garden.To study the trade-off strategies adopted by plants in terms of functional structure in the process of adapting to the environment of different life-type species that have grown in the specific environment of Jiangnan water towns for a long time.According to the adaptation mechanism of the main garden plants in the Lingering Garden based on the combination characteristics of the leaf economic spectrum,a landscape optimization strategy of"the combination of leaf economic spectrum characteristics-functional resource allocation-species selection"is proposed,in order to provide refined data for the landscape optimization of Lingering Garden plants.At the same time,it provides a method reference for the selection of species for the construction of other garden plant communities.The results of this study show that:（1）The eigenvalues of the 36 species of plants in Lingering Garden have large variation range and variability of leaf economic spectrum traits.The overall variation coefficient of leaf economic spectrum traits of plants with different life forms ranges from39.47%to 121.71%.Among the leaf traits of different life forms,the coefficient of variation of LA of arbors is the largest,which is 89.39%,and the coefficient of variation of LDMC is the smallest,which is 22.93%.The coefficient of variation of N_areaof shrub was the largest,which was 110.94%,and the coefficient of variation of chlorophyll content（SPAD）was the smallest,which was 18.02%.Both vines and herbs have the largest LV coefficients of variation,95.22%and 121.71%,indicating that compared with other traits,they had the worst stability,and the N_masscoefficients of variation were the smallest,9.47%and 15.71%.It shows that the resource allocation and utilization efficiency of each leaf functional trait are different when plants adapt to environmental changes,and the plant in the garden adopts the resource acquisition strategy during the growth process.（2）There was a general correlation between plant leaf traits at the species level,and the correlations at the functional group level were significantly lower than those at the species level.The relationship between the main leaf traits of different life forms was that SLA was significantly negatively correlated with LT,LTD,LDMC,and N_area（P<0.01）,and there were significant positive correlations between SLA and T_r,A_mass,and PNUE（P<0.05）.There were significant differences in leaf traits among plants with different life forms,and the variation range was large.Among the different life-type species,LT,LDMC and LMA all showed the trend of arbors>shrubs>vines>herbs,The SLA and N_massof herbs were significantly different from those of vines,shrubs and arbors,all showed the trend of herbs>vines>shrubs>arbors.（3）Among the 17 leaf economic spectrum trait indicators,LA,SLA,T_r,A_massand PNUE can be used as important indicators to reflect the leaf traits of the arbor layer of the lingering garden,which mainly represent the ability of plants to resist the unfavorable external environment and adapt to the hydrothermal environment.LP,LT,DW,FW,LMA and LV can be used as important indicators to reflect the leaf traits of shrubs in the mid-lingering garden,which mainly characterize the ability of plants to resist external disturbances and unfavorable environments.LA,LP,SLA,T_rand PNUE can be used as important indicators of leaf traits of vines in the lingering garden,characterizing the ability of plants to obtain resources and adaptability to dry and wet environments.LA,FW,LV,N_mass,T_rand A_areaare important indicators of leaf traits of herbaceous layers in the garden,which characterize the ability of plants to acquire resources and adapt to dry and wet environments.（4）Plants in Lingering Garden exhibit their unique plant survival strategies by forming leaf economic spectrum traits that balance development.Analysis of leaf economic spectrum traits showed that in the life form,herbs and vines were located in the position of fast investment-earning species,while shrubs and arbors were located in the position of slow investment-earning species.On the basis of the dominant species adapting to the functional group,a landscape optimization strategy of"leaf economic spectrum trait combination characteristics-functional resource allocation-species selection"is proposed,and a reasonable combination of fast investment-earning species and slow investment-earning species is proposed to further optimize the community structure.Strategies for species-type species to ensure the formation of a coexistence mechanism for the coordinated development of multiple traits and enhance community stability.Combined with the location of the leaf economic spectrum,suitable plant community structures are constructed in different habitat types and functional areas of the Lingering Garden,so as to realize the preferential combination strategy of efficient utilization of habitat resources by plants in the area.