Study On Structure And Function Of Street Trees In Hefei City

In this paper, the I-tree tools software ,developed by the United States Forest Service, was employed to study on street trees within the Second Ring of Hefei city, which including a comparison of structure and ecological benefits for street trees in main roads and typical residential area and typical schools. On the one hand, author explores the techniques using I-tree tools software to estimate ecological benefits of urban forest in China. On the other hand, provided a theoretical basis and guidance for the planting and management of street trees. And specific research includes these three aspects:(1)Based on field survey data ,I-tree tools software was used to make the analysis. The researches were paid on spices composition,structure and eco-benefits of street trees within second ring road , which cover about 100km2 . Results showed that:â‘ There are 38852 individuals of street trees classified as 16 species belonging to 13 families 14 genera. Currently, Cinamonum camphora was rated at the top of the list in order of individual number, accounting for 20.2% of total street tree population in study area,followed by Magnolia grandiflora,Platanus hispanica and Sophora japonica , these four species accounting for 68.7% of total population.Comparative study of street trees living in schools,residential areas and road ,Within the second ring road of Hefei City, show that :In this three site types, Magnolia grandiflora,Cinnamomum camphora,Albizzia julibrissin obtain the main proportion of trees ,coving the total number of 55%,and they became the local basic species.Through the dynamic comparison study on street trees in main building-up area within the first ring road from 1998-2008 , results indicated that: total 13420 street trees classified as 16 species within the first ring road was recorded in 1998, while there were only 12430 street trees in 2008. It indicated that 7.4% decline in number of trees was recorded in the period of 10 years. Ginkgo biloba ,Magnolia denudate, Platycladus orientalis recorded in 1998 are not at the list of 2008, but Sapium sebiferum,Sapindus mukorossi,Toona sinensis was added into the list of 2008.â‘¡Based on diameter at breast height( DBH ), the 65% of street trees population along major road in study area was classified as small trees (DBH <15 cm) , The tree with DBH 15-30 cm accounted for 30.4%, and trees with DBH > 30cm only accounted for 4.8%. Among Trees that DBH > 30cm, Platanus hispanica accounted for 53%.â‘¢The planting form of street trees was regarded as monotonous and lack of changes, they are mainly planted in front yard,planting trip and cutout, for example street trees in road which living in planting trip and cutout cover the total number of 99.4%,and obviously ,this pattern of planting effect the landscape and also impede healthy growth of street trees.â‘£Comparative study of street trees in different locations such as along main roads, in schools and residential areas showed that: the street trees in school yard enjoy a better healthy status, and 96% of total population being recognized health, compared to the street trees along main transportation roads that is 94.5%,while the health situation of Magnolia grandiflora is poor in these three locations , mainly due to age,disease and mechanical injury, even the species has improved its health slightly in 10 years.The 10-year comparative study on health situation of street tree population within the first ring road showed that: generally, healthy situation of street tree population is significantly declining, comparison of single tree species,the health condition of Platanus hispanica,Cinnamomum camphora,Cedrus deodara and Populus nigradeclined significantly, the health index of Platanus hispanica decline by 13%, while the health situation of Ligustrum lucidum,Magnolia grandiflora,Sophora japonica has a slight improvement.(2)About eco-benefits of street trees,the results show this:â‘ The annual eco-benefits of street trees in road is 51.458 million Yuan, the weighted average value per tree is 1324.5 Yuan. And also, there are significant different annual eco-benefits for different species: for example, per individual of Platanus Hispanic created 2811yuan every year , which is listed at the top based on benefit value for per tree; while Michelia chapensis only created 198 Yuan.Comparative study of street trees in different regions showed that: Street trees in both residential areas and along the main traffic roads have higher benefits in cut-off storm rain, reaching more than 89 percent of the total value, while that in school only cover 6.5% of the total benefits. The aesthetic benefits of street trees in school yard account for 87% of total benefits. This is mainly due to a better overall landscape in school yard, street trees easily become scenery.â‘¡The total 38852 individuals of street trees in road sequestrated Carbon of 7582 t ,which equivalent to 759.3 million Yuan ,and the weighted average benefits is195.4 Yuan per tree.â‘¢The different planting models of street trees has different effectiveness in reducing temperate, increasing humidity and improving human comfort, the planting with well designed vertical layers, such as that combined with shrubs, herbal plants and tall arbor have significant benefits. (3)At present, the conservation and management of street trees also has some problems , 14%of street trees along main transportation roads need different kinds of maintenance .After comprehensive analysis, we know that young trees neeed high level of conservation and management.