Search

This study assessed underlying natural and cultural determinants of tree health and ways to improve urban forest performance in compact Nanjing city. Two groups of factors were investigated: (1) habitat conditions, including planting site, ground-cover, land cover, and district; and (2) tree traits, including species provenance and seasonality, and tree dimensions. A stratified sampling strategy selected 6351 trees for detailed assessment. The data were analyzed by multivariate logistic regressions. Institutional, park-garden and industrial trees with more open-space sites with vegetated ground-cover performed better than roadside and residential ones. Poor trees in confined residential sites deviated from those in other cities. Park-garden sites did not always nurture meritorious, large and diversified trees. District differentiation in tree performance was related to land cover. Exotic and evergreen species grew better than indigenous and deciduous, offering hints on species-habitat matching. Detailed f...

Urban greenspaces are universally valued as amenity-recreation venues, wildlife refuges and essential livable-city ingredients. Western strategies of urban greenspace provision are difficult to implement or retrofit in most Asian cities, commonly constrained by a high-density compact form. With recent rapid urbanization and associated brown and green field developments, ample opportunities arise to overhaul greenspace standards and patterns. The case study of the ancient city of Nanjing in China permits planning for an integrated greenspace network, aiming at flexibility for future urban expansion, green field acquisition, recreational functions, wildlife habitats and environmental benefits. It consists of green wedges, greenways and green extensions that incorporate urban green areas at three landscape scales. At the metropolis scale, through normative and substantive analyses of urban form and urban expansion, and assessment of suburban uplands, five green wedges are demarcated to generate a star urban form. The green wedges link the extensive countryside to the central city, and define elongated finger-like spaces between them for urban expansion to avoid conflicts with green fields. At the city scale, three major greenways, including city-wall circular greenway, Inner-Qinhuai River greenway, and canopy-road greenway, are designed as a permeating framework to guide new greenspace location, configuration and continuity, and to link existing parks. These greenways are equipped with a comprehensive trail system to foster pedestrian and cycling movements that are preferred by the public and the government. At the neighborhood scale, a greenspace organization, consisting of residential public open spaces, shaded sidewalks and riparian strips, conforms to the network geometry. As well-connected entities, these small proximate enclaves provide opportunities for residents to have day-to-day contact with nature. They also serve to resist undue urban influences and intrusions. Overall, the three-tiered greenspace system provides an alternative mode for urban development to the conventional transport-dominated one, to usher substantial improvement in landscape-environmental quality and to augment the sustainable-city notion.

The urban landscape is by nature the result of many cultural and natural factors and processes. Cityscape associated with land attributes and human activities expresses a city's social and economic functions. Treescape in the form of species composition, tree dimension and tree performance echoes ecological and environmental functions. The cityscape can be denoted by urban factors, such as tree growing-space condition, tree management regime, human activities and planting history. The hypothesis that the cityscape plays a key role in molding the treescape is tested. Nanjing, an east China city notable for its high tree coverage, is chosen as the study area. A quantitative method has been developed to assess the relationship between cityscape and treescape. Based on statistical analyses on the surveyed results of 6527 trees and related cityscape attributes, this paper explores the pertinent patterns and underlying factors of treescape variations. Species composition has the strongest association with cityscape. Roadside and factories have lower species diversity. Residential and industrial land uses show smaller tree dimension. Trees in residential, commercial, heavy industrial land-uses perform below par. A three-way classification has been developed to examine the effects of urban factors on treescape at different cityscape scales. At the small scale, a well-vegetated groundcover will ensure better tree performance and a lower management burden. The medium-scale cityscape (land-use and habitat) is preferred in the study of treescape attributes and their spatial variations, and is suitable for urban tree planning and management.