Color Quantization And Evaluation Research On Fall-Color Trees In Beijing

As an important ornamental characteristic of fall-color trees, color is attracting more and more attention from scholars, and color quantization research of plants is appearing as a new direction in this area. On the basis of analyzing the traditional plant color quantization methods, a new method of plant color quantization by computer programming was proposed in this paper, and the color changing rule of different fall-color trees commonly used in Beijing has been summarized. At the same time, Scenic Beauty Estimation method has been used to evaluate the visual qulity of 23 kinds of fall-color trees in different discoloration periods, and their colorscape sustanability were divided into three levels by combining SBE score with the duration of their color. Based on the new color quantization method, factors that have significant effect on SBE score of fall-color trees were selected in the view of color attribution (Hue, Saturation and Value) and typical color composition, and the prediction model that aims to forecast the beauty of fall-color trees objectively has been bulit. The main findings in this paper are as follows:1.The investigation result shows that the color-changing period of 82 fall-color trees used in Beijing is mainly between mid-October and early November. Fraxinus americana ’Autumn Purple’ and Fraxinus pennsylvanica begin to color in mid-September, while the beginning of Euonymus grandiflorus and Acer griseum are in late October. The duration of color for most individuals is 10d-15d, Crataegus pinnatifida and Magnolia denudate have a worse duanation that always less than 10d, while Viburnum sargentii and Acer palmatum have a better one that more than 20d.2. Hue composition is different between trees that have different leaf colors. For yellow trees, autumn colors are mainly concentrated in yellow and orange-yellow hue; for brown (orange) trees, colors are maily concentrated in orange-red, orange-yellow and yellow hue; while for red trees, colors are maily concentrated in red, orange-red and orange-yellow hue. The proportion of high value color and high saturation color improved during the process of color-changing, but there are still some differences between different trees. In general, the yellow trees have the highest saturation and value level, and the brown (oranage) trees are both secend, while the level of the red trees are the lowest.3. Trees ordered by the number of typical colors from more to less are:the red one (33), the brown one (22) and the yellow one (18). For red trees, typical colors are distributed from red to yellow-green; for brown (orange) trees, typical colors are distributed from orange-red to yellow-green; while for yellow trees, typical colors are distributed from orange-yellow to green.4. Combining SBE score with the duration of color, the colorscape sustainability of 23 kinds of fall-color trees can be divided into three levels. Ⅰ level:species with the highest scenic beauty value and colorscape sustainability as individual, a totle of 5 kinds, can be used as singular plant trees or be planted in important areas; Ⅱ level:species with a medium colorscape sustainablility as individual and with a better one in group, a totle of 14 kinds, are more suitable for group planting; Ⅲ level:spicies with the worst sustainability, a totle of 4 kinds, are usually used to enrich the autumn colorscape.5. Correlation analysis and stepwise regression analysis result shows that factors which have significant effect on SBE score of different fall-color trees are different.In the view of color attribution:the proportion of yellow and high value color significantly affect the SBE score of yellow trees, while the proportion of orange-red and orange-yellow have signigficant effect on brown (orange) trees; and for red trees, the proportion of red and orange-red have the most obvious effect on SBE score.In the view of typical color composition:colors with have significant effect on yellow trees are concentrated in yellow and orange-yellow hue; for brown (orange) trees, those are concentrated in orange-yellow and orange-red hue; for red trees, those are concentrated in red and orange-red hue.The optimum regression equations have been built on the basis of analysis, and they can be used to predict the colorscape of fall-color trees as individual.