上海环城林带景观美学评价及优化策略

选取上海环城林带7种植物群落,采用美景度评判法,从林内景观和林外景观2个空间层次和春、夏、秋、冬4个季节,应用数量化理论Ⅰ建立了美景度和各景观因子类目之间的景观评价与预测的多元回归模型,分析了群落的结构特征和季相特征对林内景观以及外貌特征对林外景观的影响,并提出相应的优化对策。结果表明:(1)群落结构特征对林内景观的影响主要因子为胸径(平均胸径和胸径变异系数)、郁闭度和疏透度。在春季,林内美景度随着树木胸径增大而增加;在夏季,郁闭度增大会提升林内美景度;在秋季,胸径变异小的群落具有更高的林内观赏性;在冬季,疏透度对林内景观美景度影响最大。(2)群落季相特征对林内景观的影响,在各季节表现亦不同。在春季,黄色、紫色等明度较高的色相和开花量适中的群落美景度最佳;在夏季,生长势好、林冠层变化小以及树干清晰度高的群落具较高的美景度,且观花可显著提高夏季林内美景度;在秋季,色彩越纯美景度越高;而在冬季,树皮颜色深的群落美景度高。(3)群落外貌特征对林外景观有显著影响,其中林冠线对林外景观美景度影响最大,其次为林缘线。具有起伏不大林冠线和自然流畅林缘线的植物群落美景度高。旨在通过对典型植被群落不同季相的美景度评价,对上海环城林带的群落景观进行定量的评价,进而为不同情景下的群落结构优化提出相应的对策,为城市森林的群落建构与管理提供科学依据。

Optimization strategies and an aesthetic evaluation of typical plant communities in the Shanghai Green Belt

Extensive development in Shanghai during the last few decades has led to rapid urbanization. Urban lands have proliferated and the Outer Ring Road, an expressway, cannot stop the expansion and will never be a boundary between urban and rural areas. The Shanghai Green Belt, with its many species and diverse vegetation types, has become a bright spot of Shanghai's urban landscape and is a real attraction for people who desire green space for recreation and relaxation. As Shanghai has grown the aesthetic value of the Green Belt landscape has become more important and its usefulness needs to be re-evaluated to improve construction techniques and landscape management. Many researchers have shown the quality of recreational opportunities and the aesthetic values of urban forests mainly depend on the vegetation type present, the vegetative community components and the structure of the vegetative community, which can be evaluated objectively using a landscape-scale evaluation method. The scenic beauty estimation (SBE) method is based on an analysis of aesthetic trends or people's desire for a landscape. SBE is quite popular and is considered to be the most accurate method of quantifying human desires for landscape-scale management. Typical vegetation types found throughout the year were selected for SBE evaluation. We wanted to elaborate on factors influencing both forest interior and forest edge landscapes of the Shanghai Green Belt, based on an analysis of community types and structural features and to try to answer the following questions: (1) What structural features and seasonal factors have the most influence on forest interior landscapes, and (2) What factors have the most influence on forest edge landscapes and how can scenic values be enhanced through structural optimization and daily management. Seven vegetation types were selected from both forest interior and forest edge areas, in spring, summer, autumn and winter, based on Quantitative Theory I. The influence of community structure and seasonal features on forest interior landscapes and physiognomic features on forest edge landscapes was analyzed using a multivariate regression model between SBE and the measurement of every landscape factor; also relative optimization strategies were considered. The results show: (1) the main factors influencing community structural features are average diameter at breast height (DBH) and variation coefficient of DBH, canopy closure and canopy porosity. In spring, SBE increases with increasing DBH, while in summer, SBE increases with increasing canopy closure. In autumn, communities with smaller DBH variation have higher SBE values in forest interior landscapes. In winter, canopy porosity has the greatest impact on SBE values for forest interior landscapes. (2) The influence of seasonal factors changes from season to season for forest interior landscapes. In spring, communities with some bright color like yellow or purple and communities with moderate bloom have a higher SBE value. In summer, those which have vigorous growth, smaller changes in forest canopy and unobscured trunks increase the SBE value, and some flowering appears to enhance landscape beauty; the SBE value increases with color purity in autumn and the communities with dark bark have the highest SBE value. (3) The physiognomic factors of a community have a significant impact on forest edge landscape scenic beauty, to which the forest canopy line contributes the most, followed by forest edge line. Communities with a slightly undulating canopy line and complex vertical structure and natural edge line have the highest SBE value. Through aesthetic evaluation of different plant communities, we aim to provide a quantitative assessment and prediction for the Shanghai Green Belt and suggest some related strategies for community structure optimization under different conditions, and provide a scientific basis for urban forest planning, design, and management.