Choice Of Tree Species Of Changsha High-tech Zone Based On Grey System Theory

Trees are the main undertakers of green space pollution control and ecological functions in urban industrial development zones.Scientific and effective tree species selection is the key to achieve this goal.With the advancement of urbanization and the sustainable development of industrial development zones,there is an urgent need for high-quality tree species selection results.Therefore,a set of tree species selection methods which can analyze the needs of each green space from the green space scale and guide tree species selection has important significance for pollution prevention and control and ecological safety in urban industrial development zones.This study takes Changsha National High-tech Industrial Development Zone,an important urban industrial development zone in central China,as the research object.Geostatistics and various pollution assessment methods were used to explore the general situation,spatial distribution characteristics and pollution assessment of As,Cd,Cr,Co,Cu,Ni,Pb and Zn heavy metals in the soil of the study area with GIS technology,and their sources were analyzed.Meanwhile,the green space in the study area was classified by image segmentation technology,and the spatial information of all kinds of green space was obtained to jointly construct green space.Demand evaluation index.Data on the ability of tree species from 2006 to 2018 were collected by literature method,and 38 common tree species were selected as tree species selection objects.Finally,on the scale of green space,the grey system correlation evaluation method is used to calculate the selection scheme of tree species,and to analyze the results,and to infer the physiological and morphological characteristics of tree species suitable for industrial development zones.The following conclusions can be drawn:1.The pollution in the study area is more serious,especially the Cd element;the distribution of pollution is quite different;after source analysis by principal component analysis,it is found that traffic pollution sources are the main sources of heavy metals,and their contribution is slightly higher than that of industrial pollution sources.In addition,the heavy metal content in soils was divided according to different types of land use,including the four characteristic industrial types which were subdivided according to the industrial characteristics of the study area.It was found that there were significant differences not only between industrial and non-industrial land,but also between different types of industries.The other seven types of pollutants except Pb in GEMI industry are very high,and their characteristics are the most complex.2.The image segmentation based on clustering and color threshold was ·carried out on the high-definition satellite map of the study area by using matlab.After the treatment of Arcgis,277 green areas with an area of 0.0792-80.578ha were obtained,of which 9 were agricultural land.In addition,the largest proportion of green areas in residential areas was 62,which was higher than the sum of five types of industrial green areas.Then,according to the spatial information and the heavy metal pollution degree calculated based on the green boundary,the demand index is established,and the standard series of grey system correlation degree method is constructed.3.After calculating by grey relational degree method,a total of 268 tree species selection schemes were selected to correspond to each green space in the study area.Generally speaking,seven tree species,Robinia pseudoacacia,Elm,Albizzia julibrissin,Myrica rubra,Maple poplar,Ailanthus altissima and Robinia pseudoacacia,have the highest frequency and correlation degree.After analyzing the selection results,it was found that broad-leaved,medium-sized and large-sized trees,tree species with high leaf area index and high heavy metal enrichment ability generally had high correlation.It is speculated that the suitable tree species in urban high-tech zones may have the characteristics of high transpiration rate and high accumulation and transfer ability of heavy metals.4.To sum up,the index maps of tree species selection results were drawn and the index tables of evaluation results were made.On the scale of green space,the tree species selection scheme of Changsha High-tech Zone is proposed,which provides a basis for urban managers to solve the urgent need of greenbelt soil heavy metal pollution control and improve the ecological environment while pursuing the best landscape effect.