Evaluation Of High-grade Highway Greening In Northern China Plain

With the promotion of regional ecmomic increaement, high-grade highway also lead to disturbance of natural landscape. Therefore, the greening of high-grade highway attracts wide attention and raise up the standards in perspective of ecology, landscape and safety. However, current theory on high-grade highway remains in single aspect, leaving gaps to form a comprehensive and complete frame. Accordingly, researches on the rating of the high-grade highway, i.e. proposing systematically the evaluation index system and methods for high-grade highway greening, can in a sense offers theoretical and technological support for the construction and development of high-grade highway in China. This study performed evaluation index system and methods from the perspective of plant species and configuration, landscape features and overall effect through analytic hierarchy process, principal component analysis (PCA) etc. Afterwards, Beijing and Hebei sections of Jing-Shi Highway, Shi-An Highway and Lang-Tun Highway were taken as case for validaty and applicability. The main results include:(1) Evaluation index system of greening species for high-grade highway was established from ecological adaptability, biological features and comprehensive benefits. Ecological adaptability includes cold-tolerance, drought-tolerance, barren-tolerance and light-tolerance. Biological features include soil-fixing ability of root system, disease-and pestilence-resistance and pollution-tolerance. Comprehensive benefits include aesthetic value, safety, economic-efficiency and ecological benefit. Seventy-one species commonly used for high-grade highway greening in northern China were evaluated and ranked. The general performance sequence was arbors>lianas>shrubs>herbs. Meanwhile, greening plants used in median strip in Hebei section of Jing-Shi Highway were analyzed as case study.(2) Evaluation index system of configuration of high-grade road greening plants was established from the perspective of plant configuration structure, plant configuration vigor and plant configuration efficacy. The plant configuration structure contained 4 indices including species diversity, life forms, inter-species effects and species connection. The plant configuration vigor contains 4 indices involving vegetation coverage, vegetation survival conditions, vegetation growth conditions and vegetation health. The plant configuration efficacy contains 3 indices consisting ecological efficacy, safety and landscape effect. Thirteen plant configuration patterns commonly used for high-grade highway greening in northern China were evaluated and ranked. The overall performance sequence was summarized:I-level communities include Platycladus orientalis colony, Populus tomentosa - Platycladus orientalis community, Euonymus fortunei community, Amorpha fruticosa-Buchloe dactyloides community, Parthenocissus tricuspidata community and Cynodon dactylon x C.transadlensis’Tifdwarf’-Festuca rubra-Coronilla varia community, accounting for 46.15% of the overall plant configuration modes; II-level communities include Populus tomentosa community, Rosa xanthina community, Sabina chinensis-Lagerstroemia indica community and Sabina chinensis-Prunus Cerasifera community, accounting for 30.77% of the overall number of plant configuration modes; Ⅲ-level include Sabina chinensis- Rosa hybrida community, Sabina chinensis-Cercis chinensis communities and Sabina chinensis- Hibiscus syriacus community, accounting for 23.08% of total plant configuration modes.(3) Taken landscape unit as the evaluation object, landscape feature evaluation index system for high-grade roads greening was established from four aspects of landscape features, landscape quality, visual effects and vegetation environment. Landscape features include 3 evaluation indices, i.e. spatial pattern, harmony and corresponding properties. Landscape quality includes 4 indices i.e. integrity, safety, sensitivity and social culture. Visual effect includes color, diversity and visually appeals. Vegetation environment include 2 indices of vegetation coverage index and environment conditions. Landscapealong Hebei Section of Jing-Shi Highway was divided into 20 units and evaluated:there general performance was summarized:There were 4 I-level units, accounting for 20% of the total landscape units; 15 II-level units, accounting for 75% of the total landscape units; and 1 Ⅲ-level landscape unit, accounting for 5% of the total landscape units.(4) The evaluation index system for the overall effect of high-grade highway greening was established from 4 aspects of environment, safety, landscape and economic efficacy. Environment includes 3 indices of green coverage, the plant growth conditions and the green quantity ratio. The safety contains 4 indices of anti-glare function, soil-fixing slope, visual guidance and comfort. The landscape includes 3 indices of landscape pattern, landscape harmony and landscape aesthetics. The economic efficacy includes 2 indices of construction costs and maintenance costs. Evaluation was conducted on the overall greening effect of Beijing and Hebei section of Jing-Shi Highway, Shi-An Highway and Lang-Tun Highway. Overall performance were summarized as follows:Beijing section of Jing-Shi Highway (92.72)> Lang-Tun Highway (85.58)> Shi-An Highway (83.37)> Hebei section of Jing-Shi Highway (80.02), which indicated that Beijing section of Jing-Shi Highway reached the standard of excellence and the overall greening effect of the other three highway reached the standard of moderation.