Discussion on Important Role of Trees in Urban Forest

Since conducting the policy of opening and reform, urbanization is speeding in China, which helps socioeconomic development. However, environmental problems become vital as well. In the viewpoint of ecology, urban forest,which mainly consist of trees,plays an important role on the adjustment of eco-elements such as light, heat, gas, water and soil as well as protects urban-rural eco-environment. At present tree species applied in urban forest usually are monotonous, which makes city landscape looks dull. Thus the relationship between human and nature must be reformed in urban forest construction, and according to compound ecosystem theory human is the prime. For building urban forest, trees must integrate with water. Tree species selection must follow the principle of trees adapted to site conditions and employ local and wild plants especially trees so as to as early as possible expand spatially. According to measures when first branching reaches 8 m, the surroundings could be created that lower temperature in summer and fine sunlight in winter. Hence in city square construction some high trees must be planted together with scrubs, lianas and herbs so that huge umbrella-ship crown could be formed and bring ecological benefits spatially. Additionally climbers must be paid attention as are characterized with wide adaptation, strong drought tolerance and climbing capacity, so that they are not only applied in greening dessert, bare mountain and hills, also in urban area, bridges and roads.