Species composition of stone wall trees
Families and genera of stone wall trees
There were 96 stone wall trees belonging to 6 genera and 5 families in Macao. Among them, Moraceae and Ficus appeared the most frequently, both reaching 85 times, accounting for 88.5% (Table 1). It showed that Moraceae, a kind of tropical distribution family, was dominant in the stone wall trees communities, which meant that stone wall trees species in Macao appeared distinctly tropical nature18.
Species of stone wall trees
There were 16 species of the stone wall trees in Macao including Bridelia tomentosa, Celtis sinensis, Eriobotrya japonica, Ficus altissima, F. benjamina, F. elastica, F. hispida, F. microcarpa, F. pandurata, F. subpisocarpa, F. tinctoria subsp. gibbosa, F. rumphii, F. variegata, F. virens, Leucaena leucocephala, and Trema cannabina (Fig. 2).
16 species of stone wall trees in Macao (photo was taken by Professor Qin Xingsheng).
Based on the frequency of occurrence of various tree species, the frequency was concentrated in the range of 1–5%. Among them, Ficus microcarpa had the highest frequency, reaching 58 times, with a frequency of 60.4% (Fig. 3). This tree species is robust, adaptable and fast growing, which is the main population of Ficus19.
Frequency distribution of stone wall tree species in Macao.
Stone wall trees in the historic center of Macao
The historic center of Macao, covering an area of about 2.8 km2, is the heartland of Macao’s historical and cultural heritage, which plays a significant role in the cultural heritage around the world18. The historic center of Macao provides valuable historical and cultural resources that enable Macao to transform into a world tourism 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 trees in the survey. Among them, Jardim Luís de Camões has the largest number of 9 stone wall trees. The park, built in the mid-eighteenth century, is one of the oldest gardens in Macao and has the largest number of old trees in Macao. The park had provided good time and environmental conditions for the growth of stone wall trees.
(a) Schematic diagram of distribution and number of stone wall trees in the historic Center of Macao. (b) Schematic diagram of historic center of Macao. (URL of the Macao map: https://www.d-maps.com/m/asia/china/macau/macau02.gif).
According to Decree No. 56/84/M of the Macao Special Administrative Region Government Printing Department, immovable property that represents the creation of man, or the development of nature or technology and has cultural significance is considered tangible cultural property. The occurrence of the stone wall tree was inextricably linked to ancient wall-building techniques of that time, which was of great significance for the study of the technological development and ecological landscape of the historic center of Macao. The concept of “historic urban landscape” was proposed by Zhang Song20, who argued that cities were organisms in continuous evolution, emphasizing respect for the interrelationship between natural and man-made environments. The stone wall trees in the historic center of Macao have been associated with the local culture and ecology tightly and should be preserved as important urban landscape.
Symbiotic relationship between tree and stone walls
As shown in the table below (Table 2), it was found that most of the stone wall trees had root systems that were not only superficially attached to the wall but also extended to the top or bottom of the wall. In particular, Ficus spp. whose strong root system could closely mosaic with the wall, thus forming a strong symbiosis.
Stone walls can imitate the traditional nature-accommodating features to permit spontaneous establishment of a diverse plant assemblage. Besides vegetative diversities in terms of species composition, growth form and biomass structure, stone walls can support a mass collection of urban wildlife and provide various ecosystem service. It is highly recommended that modern urban design be created to embrace stone wall landscape as an integral part of naturalistic or ecological design.
Vision for the establishment of the stone wall tree trail system in the historic of Macao
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 the stone wall trees and walls, together with the traditional streets, form a spatial urban landscape. Starting from the location of the stone wall tree landscape, the dots and lines are prospective to promote the establishment of a comprehensive stone wall tree landscape trail system (Fig. 5), so that the public can make use of the existing biological resources to have a better understanding of the land on which they live.
Schematic diagram of the stone wall trees trail system on the Macao Peninsula (URL of the Macao map: https://www.d-maps.com/m/asia/china/macau/macau02.gif and the finished map is created by Meisi Chen through the Photoshop CS6 and Arc GIS 10.2).
Since 2012, the Macao Government has been implementing the “Strolling along Macao Street” project, which aims at studying and exploring the history and culture of the streets of Macao through an in-depth cultural tourism route and promoting it to different levels of society. The establishment of the stone wall tree trail system can rely on this project to raise the public’s awareness of the protection and cultural identity of the stone wall tree landscape through a variety of ways. For example, route design competition, photography competition and exhibition, recruitment of “Stonewall Tree Protection Ambassadors” and other forms of participation, so that the public could complete the “role change” in the high degree of such participation—from “onlookers” to “bystanders”.
Survey results of associated plant species
Species composition and occurrence of frequency
The survey showed that there were 101 species of stone wall tree associated plants in Macao, under 88 genera and 51 families. Most associated plants belonged to Euphorbiaceae, Compositae, and Araceae.
There were 85 species with a frequency of 1–5 times, accounting for 84.2% of total species. A total of 11 species appeared 11–15 times, accounting for 4.0% (Fig. 6). There were a total of 4 species that appeared more than 15 times. They were Cocculus orbiculatus, Pteris cretica, Paederia scandens, and Pyrrosia adnascens. Most of the associated species appeared only 1–5 times, indicating that most plants were selective and accidental for the growth conditions of stone wall sites.
Occurrence frequency in various species of associated plants.
Life form composition
Herbaceous plants with 37 species, accounting 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 propagated to the wall surface by wind force.
Life form of associated plants with stone wall trees in Macao.
Similarity analysis of the associated plants in Macao
In order to compare the similarity of associated plant species in different environment, the surveyed sample sites for this study were divided into three categories: motorized lanes, non-motorized lanes, and park habitats (Table 3). According to Jaccard’s similarity principle, Sj is extremely dissimilar when it is 0.00–0.25, and the analysis showed that the similarity of companion plant species in all three habitats was extremely dissimilar. Therefore, it indicated that the companion plants in different habitats had obvious diversity and uniqueness.
Source: Ecology - nature.com
