The Biodiversity And Carbon Storage Of Urban Trees In Xi’an City

The role of biodiversity protection and carbon storage for urban vegetation is more prominent along with the acceleration of global urbanization. The type, quantity,size, height and diameter of all trees in 246 plots were investigated in inner area of Xi’an beltway. The tree biodiversity were analyzed and the carbon storage of tree in different functional area was calculated on the basis of allometric equation. The objective is to provide a scientific basis for sustainable urban development and urban greening. The main results are as follows:(1) There are 68 kinds of trees in Xi’an belonging to 36 families and 63 genera.The evergreen trees have 18 kinds with 18.78% of total belonging to 11 families and19 genera. Correspondingly there are 50 kinds of deciduous trees belonging to 44 genera and 30 families. The ratio of evergreen trees and deciduous trees is 2:9. In all trees, the native tree species, such as Sophora japonica, Populus tomentosa,Persimmon paulownia and Ailanthus altissima, is 47.25% of total. The vegetation structure is imbalance due to high ratio of several dominant tree species(Sophora japonica, Platanus acerifolia,Ligustrum lucidum).(2) The DBH of urban trees was 25-30 cm, this shows that urban trees of Xi’an are most in childhood. The DBH and height of urban trees are approximately the normal distribution. For different functional area, trees are good and huge in educational and industrial area.(3) The Patrick index, Margalef index, Simpson index, Shannon-Wiener index,Pielou index of urban trees biodiversity was 3.84, 0.75, 0.43, 0.81 and 0.57(4)respectively. The biodiversity difference for each functional area is obviously,and scenic spot is higher and road area is relatively lower. The biodiversity level of alien species is higher than native species. In Xi’an, the trees diversity level in new city zone is better than that in old city zone.(5) In Xi’an, the carbon storage of urban trees in educational area is highest with14.24 kg/㎡, then that in scenic area is 6.41 kg/㎡, commercial area 4.55 kg/㎡ and industrial zone 3.20 kg/㎡. The urban trees carbon storage in road was calculated 48.23 kg per meter. The tree carbon storage is associated with tree species and DBH. The capacity of carbon sequestration in Platanus acerifolia is more, then Ligustrum lucidum, Sophora japonica and Populus simonii. The carbon storage that trees fixed in old city zone is relatively higher than that in new city zone.