A framework for the study of natural landscape in historic cities
Ecological, spatial, and symbolic dimensions of natural landscape
The notion of heritage has been categorized into natural and cultural, and cultural heritage into tangible and intangible heritage (Yang 2011). While such categorization may' have some theoretical and practical utility', a study of nature in a historic urban area needs to blur the boundaries of these categories and form a different way to understand its role in urban places. The natural landscape in historic urban areas could be studied in terms of the ‘ecological landscape’, ‘spatial landscape’, and ‘symbolic landscape’. The ecological landscape includes the geographical features such as topography, geomorphology', hydrology, mountains, bodies of water, vegetation and other bio-organisms. The spatial landscape is the physical enclosure, viewshed, visual sightlines/axes, skyline, scenic locations, spatial sequences, and similar visual-spatial characteristics and experiences that are formed by the features of the natural landscape. The ecological landscape is about the entire natural ecosystem that provides the base for the historic urban area. The spatial landscape is about specific places created by the natural landscape. The symbolic landscape refers to various intangible cultural expressions associated with the natural landscape of the historic city that include belief systems, values and meanings, and cultural practices. These categories of ecological, spatial, and symbolic landscapes are interrelated with and interdependent on each other; the classification is therefore simply for the practical purpose of their study and conservation.
These dimensions of natural landscape play an important role in the understanding of the formation and characteristics of the urban fabric in historic Chinese cities (Yang 2003). How some aspects of these dimensions define the form and experience of such cities are briefly explained below.
The ecological base of urban form
The unique form and growth patterns of historic cities are significantly influenced by the distinctiveness of the ecological base of their natural landscape. For a majority of historic Chinese cities, the selection of the location for their urban settlements has always been a relatively flat terrain with surrounding mountains and rivers, which provided materials for sustaining life and to develop connections and communication with the world outside. Other factors such as geology, climate, and fauna and flora of the ecological base also had influence on the formation, shaping and development of urban landscapes, the socio-cultural practices of their residents, and economic systems including agriculture and other industries (Yigang 1994). Aspects of geology and vegetation critically influenced the type of construction material and technology available and in turn the character of these urban settlements (Margottini and Spizzichino 2015). Geological factors that make locations susceptible to earthquakes, landslides, and flooding also determine the patterns of the urban built fabric and settlements. The multiple aspects of the ecological base of an environment, therefore, have a greater influence of the shape, form, and traits of urban settlements, including its extent, patterns of urban blocks and street network, building stock, and the overall sense of the place (Qing 2008). Urban conservation efforts usually keep the protection of this urban structure as the central focus. As the urban form is also determined by the natural ecological base of the place, that base landscape should also be safeguarded for a proper conservation of historic urban areas.
The network of urban green spaces
A network of urban green spaces is formed by the interaction of various greeneries of different types and scale within an urban environment. It plays an important role in the integration, shaping, and strengthening of urban features within a historic urban area (Yang 2011). Urban green spaces may include a specific historic tree (‘heritage trees’), streets and urban squares with trees and other vegetation, small plots of land like a home garden with trees, flowers and plants, as well as large-scale areas such as forests, grasslands, parks, nature reserves, and agricultural lands within and around an urban area. Linear, contiguous green spaces such as historic canals, cultural routes and greenways also fall within the latter category and could be defined as ‘heritage corridors’. Urban green spaces are part of the ecological landscape of the place; they contribute immensely for the definition and formation of the palpable spatial experience (thus, the spatial landscape), the generation of a pleasing micro-climate, and the evocation of a restorative sense of place in a historic urban area.