Species Characteristics and Cultural Value of Stonewall Trees in Macau Urban Area
Stone wall tree species composition
Families and Genera of Stonewall Trees
There were 96 stonewall trees belonging to 6 genera and 5 families in Macao. Among them, the Moraceae and ficus occurred most frequently, both reaching 85 times, or 88.5% (Table 1). He showed that Moraceae, a kind of family with tropical distribution, was dominant in stonewall tree communities, which meant that stonewall tree species in Macao appeared distinctly tropical in nature.18.
Stone wall tree species
There were 16 species of stone-walled trees in Macau, including Tomentose bridelia, Celtic sinensis, Eriobotrya japonica, Ficus altissima, F. benjamina, F.elastica, F. hispid, F. microcarpus, F.pandurate, F. subpisocarpa, F. tinctoria subspecies. gibbosa, F. rumpii, F. variegata, F. virens, Leucaena leucocephalaand Trema cannabina (Fig. 2).
Based on the frequency of occurrence of various tree species, the frequency was concentrated in the range of 1-5%. Among them, Ficus microcarp had the highest frequency, reaching 58 times, with a frequency of 60.4% (Fig. 3). This tree species is hardy, adaptable and fast growing, which is the main population of ficus19.
Stone wall trees in historic center of Macau
The historic center of Macau, covering an area of approximately 2.8 km2is the heart of historical and cultural heritage of Macau, which plays an important role in the cultural heritage of the whole world18. The historic center of Macau provides valuable historical and cultural resources that allow Macau to develop into a world tourist center20.
A total of 14 plots were located in the historic center of Macao (Fig. 4), with 45 stone wall trees, accounting for 47.9% of the total number of survey trees. Among them, Jardim Luís de Camões has the largest number of trees with 9 stone walls. The park, built in the mid-18th century, is one of the oldest gardens in Macau and has the largest number of old trees in Macau. The park had provided good temporal and environmental conditions for the growth of the Stonewall trees.
According to Decree No. 56/84/M of the Printing Department of the Macao Special Administrative Region, real estate which represents the creation of man or the development of nature or technology and which has a culture are considered tangible cultural property. The appearance of the stone-wall tree was inextricably linked with the ancient wall-building techniques of the time, which was of great significance for the study of technological development and the ecological landscape of the historic center of Macao. . The concept of “historic urban landscape” was proposed by Zhang Song20, who argued that cities were continuously evolving organisms, emphasizing respect for the interrelationship between natural and man-made environments. The trees of the stone walls of the historic center of Macau have been closely associated with the local culture and ecology and must be preserved as an important urban landscape.
Symbiotic relationship between the tree and the stone walls
As shown in the table below (Table 2), most rock wall trees were found to have root systems that were not only superficially attached to the wall, but also extended upwards or the bottom of the wall. Specifically, ficus spp. whose strong root system could closely mosaic with the wall, thus forming a strong symbiosis.
Stone walls can mimic traditional characteristics of adapting to nature to allow spontaneous establishment of a diverse plant assemblage. Besides plant diversities in terms of species composition, growth form and biomass structure, stone walls can support a massive collection of urban fauna and provide various ecosystem services. It is highly recommended to create a modern urban design to incorporate the stone wall landscape as an integral part of the naturalistic or ecological design.
Vision for the Establishment of the Stone Tree Trail System in Historic Macau
The traditional street environment in the Macao Peninsula is a kind of distinctive urban landscape, which can highlight the specificity and value of the urban context. The combination of stone walls, trees and walls, together with traditional streets, form a spatial urban landscape. Starting from the location of the stone wall tree landscape, the points and lines are forward-looking to promote the establishment of a comprehensive stone wall tree landscape trail system (Fig. 5), so that the public can use the existing biological resources to have a better knowledge of the territory in which they live.
Since 2012, the Macau government has been implementing the “Walk along Macau Street” project, which aims to study and explore the history and culture of Macau’s streets through an in-depth cultural tourism route and promote it at different levels of society. The establishment of the Stonewall Tree Trail Network can build on this project to raise public awareness of the protection and cultural identity of the Stonewall Tree Landscape in various ways. For example, a route design contest, a photography contest and exhibition, the recruitment of “Stonewall tree protection ambassadors” and other forms of participation, so that the public can complete the “change of role” in the high degree of such participation – from “spectators” to “passers-by”.
Results of the survey of associated plant species
Species composition and frequency occurrence
The survey showed that there were 101 plant species associated with Stone Wall Trees in Macau, divided into 88 genera and 51 families. Most of the associated plants belonged to the Euphorbiaceae, Compositae and Araceae.
There were 85 species with a frequency of 1 to 5 times, representing 84.2% of the total species. A total of 11 species appeared 11–15 times, accounting for 4.0% (Fig. 6). There were a total of 4 species which appeared more than 15 times. They were Cocculus orbiculatus, Pteris cretica, Paederia scandensand Pyrrosia adnascens. Most associated species only appeared 1-5 times, indicating that most plants were selective and accidental for the growing conditions of the stone wall sites.
Composition of life form
Herbaceous plants with 37 species, accounting for the percentage of 52.3% (Fig. 7), were dominant in the associated plant species because the seeds of herbaceous plants are lighter and can be spread on the surface of the wall by the force of the wind.
Similarity analysis of plants associated with Macau
In order to compare the similarity of associated plant species in different environments, the sample sites surveyed for this study were divided into three categories: motorized pathways, non-motorized pathways, and parkland habitats (Table 3). According to Jaccard’s principle of similarity, SI is extremely dissimilar when it is 0.00 to 0.25, and the analysis showed that the similarity of companion plant species in the three habitats was extremely dissimilar. Therefore, this indicated that companion plants in different habitats had obvious diversity and uniqueness.
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