The Classification And Character Analysis Of Urban Forest In The Downtown Of Chongqing

Urban forest plays an extremely important role in maintaining and improving the urban ecological environment, promoting the quality of living circumstances and creating livable city. However, because of the deviation in understanding the urban forest, there is no unified classification and standards and the development of urban forest has been inhibited. Therefore, a reasonable classification is the basis and precondition for planning and constructing the urban forest.This paper studies the urban forest in the downtown of Chongqing which lays within the outer expressway of Chongqing. The urban forest distribution map is made by combining field study with aerial photo in the scale of 1:25000 and some help from AutoCAD, Photoshop and other image processing software. The paper applies the principles and methods of landscape ecology, classifies the urban forest in three standard forms: forest vegetation types and canopy density; forest patch size; forest patch shape Qualitative and quantitative analysis are made according to different forest composition and regional distribution characteristics. The paper aims to discuss the composition and distribution of urban forest in the downtown of Chongqing. The built-up area and non built-up area are analyzed. The paper focus on the distribution of urban forest in various areas with different density in the built-up area in order to provide reference to the construction of Chongqing urban forest.The results are as follows:(1)The downtown of Chongqing has coverage of 27.26% of urban forest which has a considerable distance to the national standard or the developed countries. The distribution of the downtown of Chongqing urban forest is very uneven. The majority is in the Zhongliangshang Mountain and Tongluoshan Mountain, it's obviously insufficient in the built-up area where the population is concentrated. This situation has limited the ecological benefits.(2)In the system of forest vegetation types and canopy density, the coniferous forest concentrates in the place that has an altitude of more than 400m in Zhongliangshan Mountain, Tongluoshan Mountain and some other mountains. The higher altitude, the less disturbance made by human activities, this is the reason that the coniferous forest has high canopy coverage and dense forest. Broad-leaved forest is mostly distributed in the hills below 400m above sea level. Due to serious human disturbance, the distribution of scattered broad-leaved forest is scattered and the canopy coverage is low. In addition, Mingled forest lays along the edge of coniferous forest(3)In the system of forest patch size, large forest (area> 50hm~2) occupies 63.84% of the total forest area, however, its number of patches only occupies 2.31% of the whole. On the other hand, small and medium-sized forest (area< 1hm~2) accounts for 1.69% of total forest land, but the number of patches accounts for 47.17% of total forest patches, showing that the polarization of the urban forest is very serious. As opposed to large forest patches, the small-scale and small medium-sized forest patches are insufficient.(4)In the system of forest patch shape, group forest dominants in size and quantity, respectively 54.73% and 49.99%. This could fully explain that under the human interference, the urban forest patch shape in Chongqing stands close to regularization. Opposed to the group and banding forest, the linear forest area accounts for only 2.71% total area of forest land, seems grossly inadequate.(5)The regional distribution analysis of forest size shows that small and small medium-sized forest patches mainly scatter in the built-up areas which have high building density. While medium and large forests distribute mainly in built-up areas that are mostly city parks, central ridge line and natural hills with medium and low building density. Large forest patches are found in the non-built up area in natural mountains, the distribution is concentrated and continuous.(6)The regional distribution analysis of forest shape shows that group forest mainly distributes in built-up area especially in the high building density area. Linear forest has a large number but small area in the built-up area, this is especially obvious in high building density area. The majority of banding forest lays in Zhongliangshan Mountain and Tongluoshan Mountain and along both the sides of Yangtze River and Jialing River, the distribution is relatively concentrated and continuous.