Study On Root Characteristics And Landscape Effects Of Plant On Polluted Sites In Shanghai Relocation Site

In the context of new urbanization development,urban land is becoming increasingly tight,and relocation sites represented by housing demolition sites,factory relocation sites,and pollutant treatment plants are gradually becoming the main types of sites for urban green space construction.However,soil contamination is common in relocation,and the use of phytoremediation technology to purify soil is recognized as a green,safe and ecologically effective method.At present,there are more studies on the selection of remediation plants and heavy metal enrichment capacity,but there are fewer studies on nondestructive detection of the root system of remediation plants in relocation sites.With the rapid development of science and technology,tree radar detection technology has been widely used.In this study,a typical relocation site in Shanghai,the World Expo Cultural Park,was used as a test site to investigate the root systems of Magnolia grandiflora,Cinnamomum camphora,Platanus acerifolia,Koelreuteria bipinnata ’integrifoliola’,Aesculus chinensis,Sapindus saponaria,six common tree species with heavy metal enrichment capacity in the garden,were scanned and probed,and the root density and spatial distribution were statistically analyzed,and the influence of underground root distribution characteristics of garden plants on above-ground plant configuration and landscape effects based on the combination of above-ground landscape spatial structure and underground root levels will be analyzed,with the following main conclusions:(1)Horizontally,the overall root density shows a decreasing trend with distance from the trunk,with the greatest decrease within 1-2m,and the decrease is gradually stabilized with the distance from the trunk gradually increasing.In the vertical direction,the root density was greatest in the 61-119 cm soil layer,and the root density in the soil layer above and below this depth increased more slowly with the growth of trees.A few trees can reach a root depth of 119 cm or less.(2)According to the basic shape of the root profile,Class I Magnolia grandiflora,Cinnamomum camphora and Sapindus saponaria are obviously rectangular,and Class II Platanus acerifolia,Koelreuteria bipinnata ’integrifoliola’ and Aesculus chinensis are triangular.The root growth characteristics were analyzed according to the growth type differences of the root density in the soil depth layer of the profile map.Magnolia grandiflora and Platanus acerifolia were shallow root trees,and Koelreuteria bipinnata ’integrifoliola’,Cinnamomum camphora,Aesculus chinensis and Sapindus saponaria were deep root trees.There are two types of spatial distribution of tree root systems: 1.Horizontal root systems of Magnolia grandiflora and Platanus acerifolia;Two types of vertical root system Cinnamomum camphora,Sapindus saponaria,Koelreuteria bipinnata ’integrifoliola’,Aesculus chinensis.(3)Landscape effect analysis in three different community sample sites,sample site type 1: spatial structure is relatively simple,planting methods are column planting,can be divided into flowering,foliage,fruit-bearing species,color is slightly monotonous to green-based,with open space,simple atmospheric landscape effect.The underground space structure is simple,the utilization rate of soil layer is low,and the efficiency of plant restoration is slow.Sample plot type 2: The spatial structure and landscape levels are clear,and the planting methods are forest planting and column planting,with a variety of tree species,rich colors and obvious seasonal characteristics.It is a more reasonable configuration of plant combination.The planting method is more reasonable.The underground space structure is rich,and most of the three layers of soil space are reasonably used,with high restoration efficiency.Sample Site Type 3: Simple spatial structure,various planting methods,more flowers and herbs,and strong color contrast,which is the best configuration for ornamental effect.However,for the restoration effect only the shallow soil has a strong restoration effect,and the middle and lower soil restoration efficiency is low.Although tree radar can be non-destructive detection of tree root system,but the current root system research is still limited,for the root system size detection is mostly limited,can not be completely fine detection,the future still need a lot of in-depth research.Whether there are interactions between root systems of different tree species and whether artificial maintenance activities are the cause of low root growth in the shallow soil layer are expected to be further investigated in the future.