上海环城林带景观美学评价及优化策略

Abstract

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.