| In this paper 3S technology combined with spot investigation was employed to analyze both Leaf Area Index (LAI) and tree canopy coverage (TCC) of Urban forest patch intensively within the second ring road and several economic developing zones in Hefei, The study area covers about 363km~2. Its current distribution in satellite-pictures is mastered by the means of ArcGis software; Regression model between LAI and Normalized Difference Vegetation Index (NDVI) was built by the inverse method of LAI, where LAI and its area are calculated by the use of NDVI. Then the total leaf area and its distribution pattern in the study area was acquired.Besides, 3200 screenshots intercepted by the tool of Googleearth software at 500 meters high in the sky,a proper resolving power for crown contour distinguish , are composed in the Photoshop software to form a complete aerial photograph of research area. Based on functional classification principles, totally 7 land use categories, such as road, water surface, universities and official organizations, primary and middle schools, parks, residential districts and others, was identified. As Crown contour was made out and leaf area was derived for each land type, the dimensional and three dimensional green quantity was calculated by its area multiplying average LAI and average crown height respectively. The results indicated that:(ⅰ) Based on NDVI of RS data and field measurement of LAI of urban forest using Winscan canopy analyser. the relationship between NDVI and LAI was built in the paper, which was described by logistic equation. This method also could be employed to estimate leaf area in neighboring districts.(ⅱ) Average LAI of 2.07 m~2/ m~2 for urban forest patches within the second ring road was estimated directly using of plant canopy analyzer, and 2.29 m~2/ m~2 in entire research area Among seven land use categories, LAI of urban forest patches in universities and official organizations, primary and middle schools and others, whether within the second ring road or in entire research area, are the lowest, road layer lower, residential districts, parks and public plazas highest.(ⅲ) The total leaf area within the second ring road is 798.18×104 m~2, its main distribution scopes are parks, such as ring park and Xiaoyaojin Park, its LAI are 2-3 m~2/ m~2 in the midst of; The leaf area of whole study area is 5159.11×104 m~2, its main distribution scopes are in western and northwestern part of the city, its LAI are mostly between 3 and 4 m~2/ m~2 , because of Shushan forest park existing in the region.(ⅳ) Within the second ring road, green quantity contribution in residential districts, parks and plazas is higher than that of urban forest coverage; But it is lower in universities and official organizations, primary and middle schools, roads and others. In entire research area, green quantity contribution in residential districts, parks, plazas and roads are higher than that of urban forest coverage; But green quantity contribution in universities and official organizations and primary and middle schools are generally equal to that of urban forest coverage; the others are lower.(ⅴ) The tree canopy coverage reached to 8.2% within the second ring road, yet 6.5% in entire research area. Although total tree canopy area is highest in residential districts, its coverage is lower; Total canopy area in parks is relatively lower but its coverage is the highest.According to the current status of urban forest in Hefei city, the author thinks that we shall protect forest belt round the center city and plant more street trees complying with the design principle of interspersed arbors and shrubs, especially in high density residential districts. Meanwhile, we shall carefully preserve current urban forest in the southwest and southeast of urban area and increase urban forest area in the northeast and northwest to alter its uneven distribution in Hefei. Finally, we shall further construct an intact system of urban forest. |
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