Studies On Urban Forest Structure And Potential Greening Space In Beijing Built-up Area

By investigating the growth characteristics of trees in Beijing built-up area, including 40 parks and recreations, 194 streets and water areas, 50 enterprises and institutions and 25 residential areas, the tree species composition and health condition of urban forest were analyzed and its space structure characteristics were also studied on the distribution of tree DBH (diameter at breast height) and tree stratum. The methods of calculating and evaluating ROGS (radiate occupation of green space) of urban forest were discussed on emphasis. And the present ROGS and potential ROGS of the built-up area were calculated and analyzed. Based on these, some suggestions were afforded for urban forest construction and green space extension which included tree species selection, management, cultivation and vertical greening. The results were as follows.1. According to the composition and distribution of species, three dominant species (Sophora japonica, Populus tomentosa and Platycladus orientalis) occupied 53.1% of the total trees in the study areas. The average density of urban trees was 156 tree · hm^-2. The sequence of the density of different land types was that: parks and recreations (225 tree·hm^-2)> streets and water areas (181 tree · hm^-2)> enterprises and institution areas (54 tree · hm^-2)> residential areas (30 tree · hm^-2). Furthermore, the average density of big trees (height ≥ 20m) was 2.4 tree · hm^-2 and the highest and the lowest density respectively were the enterprises and institution areas (4.2 tree · hm^-2) and the residential areas (1.6 tree · hm^-2). The dominant big tree species mainly included Populus tomentosa, Platanus hispanica, Sophora japonica, Platycladus orientalis, Ginkgo biloba, Cedrus deodara and Fraxinus pennsylvanica.2. The distribution of trees in DBH showed a tendency of "great number ones in middle...