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The world’s fast pace of urbanization has exerted profound pressure on urban trees. With over 400 years of urban history, Macau has developed an exceptionally high population density and ultra-compact mode, yet it permits survival of interesting and diverse heritage trees. These outstanding living remnants connote special values in history, ecology and botany. In conjunction with commemorative importance, they have been designated as Old and Precious Trees (OPT). This study evaluated the OPT with reference to: (a) species diversity and evenness; (b) spatial distribution; (c) tree dimensions, age and health; and (d) spatial differentiation of tree attributes by four districts and eight tree-habitats. Heritage trees in Macau were compared with those in Hong Kong and Guangzhou. The 793 OPT belong to 63 species. The exotic Ficus rumphii is overwhelmingly dominant, followed by F. microcarpa , Cinnamomum camphora and Dimocarpus longan . Species composition, age distribution and health conditions are associated with tree-habitat. Roadside has the largest number of OPT but the least species richness. Public parks and gardens has the highest diversity and largest tree dimensions. The oldest trees are clustered in urban parks and religious places. Tree health is poorer at roadsides, and private residential and commercial properties. The patterns suggest close relationship between tree traits and physical fabric of the city. However, the variety rather than duration of geographical contacts is a key determinant of urban tree diversity. The findings offer insights for heritage-tree conservation and management strategies in compact cities with similar urban structure and history. [ABSTRACT FROM AUTHOR]

As an increasing proportion of the global human population resides in urban areas, urban forests are becoming both more important and more threatened. In many cities urban tree cover conflicts with strategies for urban intensification, and is being reduced due to inadequate protection. Here, we assess the effectiveness of one type of tree protection policy used by a number of cities worldwide: the case-by-case protection of specific individual trees. We use Auckland, New Zealand as a case study, where the main form of urban tree protection is now through Auckland Council's Schedule of Notable Trees. We investigated: (1) the species composition of the listed trees, and (2) the relative contribution of geographical variables (suburb age, dwelling density, socio-economic deprivation, and tree cover) in explaining spatial variation in listed-tree density. Tree cover (>8 m) in central Auckland was 6% of the land area, 63.2% of which was on private land. Of these trees, approximately 15% were protected. The tree species protected reflected cultural heritage; popular species were protected in large numbers, whilst only a single individual of a threatened native species was protected. The highest numbers of listed trees were in older suburbs, those with higher density housing, and those with lower levels of socio-economic deprivation. A low correlation between vegetation cover and listed-tree density shows that the proportion of trees protected varies substantially in different areas. We conclude that this case-by-case tree protection strategy provides insufficient protection for Auckland's urban biodiversity, but better implementation would improve biodiversity and social outcomes. [ABSTRACT FROM AUTHOR]

Abstract: Public housing estates (PHEs) in Hong Kong, accommodating 3.3 million of the 7-million population, have generous landscape planting in their grounds. The independent tree management regime generates a tree stock that deviates from the general urban-tree population. This study evaluated species composition, floristic diversity, importance value, and spatial distribution of trees in 102 PHEs (half of the total) occupying 8.31km2 (territory land area of 1104km2), assessed their contribution to urban biodiversity, and developed a species selection strategy to enrich urban biodiversity. 48,823 trees belonged to 232 species, 151 genera and 59 families. Natives contributed 69 species and 10,837 trees. Species profile was skewed toward exotic species and trees. The species were divided into six frequency groups. The signature group had 45 species each with >200 trees. The dominant, common and occasional groups had 20, 26 and 48 species, respectively. 59 species in the rare group and 34 in the solitary group denoted changing and diverse species selections, respectively. Nonmetric Multidimensional Scaling (NMDS) found that species distribution in PHEs was strongly associated with species diversity, estate area and estate age. However, district and region were not correlated with NMDS. Some 98 species were significantly correlated (Spearman) with one or both NMDS axes. Species groups were analyzed to inform a species selection strategy to improve future planting program and enrich urban biodiversity. The methods and findings could be applied to south-China and other cities to rationalize urban-forest programs with the help of objective research data. [Copyright &y& Elsevier]

Abstract: Heritage trees in a city, echoing factors conducive to outstanding performance, deserve special care and conservation. To understand their structural and health conditions in urban Hong Kong, 30 defect-disorder (DD) symptoms (physical and physiological) subsumed under four tree-position groups (soil-root, trunk, branching, and crown-foliage) and tree hazard rating were evaluated. The surveyed 352 trees included 70 species; 14 species with 233 trees were native. More trees had medium height (10–15m), medium DBH (1–1.5m) and large crown (>15m). In ten habitats, public park and garden (PPG) accommodated the most trees, and roadside traffic island (RTI) and public housing estate (PH) had the least. Tree dimensions and tree habitats were significantly associated. The associations between the 2831 DD and tree-position groups, tree habitats and tree hazard rating were analyzed. Fourteen trees from Ficus microcarpa, Ficus virens and Gleditsia fera had high hazard rating, 179 trees from 22 species moderate rating, and 159 trees from 55 species low rating. RTI, roadside tree strip (RTS), roadside tree pit (RTP), roadside planter (RP) and stone wall (SW) had more moderate hazard rating, and PPG, roadside slope (RS) and government, institutional and community land (GIC) more low rating. Redundancy analysis showed that DD were positively correlated with RTS, RTP, RP and SW, but negatively correlated with PPG, RS and GIC (p <0.05). The DD significantly increased tree hazard rating and failure potential. Future management implications for heritage-tree conservation and enhancement focusing squarely on critical tree defect-disorder in urban Hong Kong were explored, with application to other compact cities. [Copyright &y& Elsevier]

Abstract: Heritage trees play special ecological, historical and landscape roles in cities. The officially designated old-valuable trees (OVTs) in Hong Kong, threatened by urban intensification and improper care, demand deep understanding to inform management and conservation. This study evaluated their floristic diversity, biomass structure and importance value, and spatial pattern and differentiation by districts and tree-habitats. Data analysis was assisted by detrended correspondence analysis (DCA), similarity percentage analysis (SIMPER) and other statistical tests. New indices, namely district dissimilarity index (DDI), district heterogeneity index (DHI), habitat dissimilarity index (HDI) and habitat heterogeneity index (HHI) helped to assess spatial differentiation. The 352 OVTs belonged to 70 species, 56 genera and 36 families. Ficus microcarpa dominated with maximum importance value, accompanied by only three common species. Some 22 rare and 44 solitary species denote diverse origins due to inheritance and cultivation. Moraceae and Ficus were the dominant family and genus. The oldest districts accommodated more species, trees, and unique species, whereas newer districts had notably less. DCA showed higher floristic fidelity in old districts, and three common Ficus species were ubiquitous in districts. SIMPER results showed the highest DDI and lowest DHI in the newer district. Public park and garden (PPG) habitat harbours most species, trees, and botanical uniqueness. Three Ficus species were also ubiquitous in habitats. Public housing and PPG had the highest HDI. District and habitat dissimilarities were mainly contributed by dominant and common species. Management implications with reference to preservation and enhancement of OVTs were explored, with applications for other cities. [Copyright &y& Elsevier]

Recent rapid urbanization of Guangzhou in south China has degraded its rich urban-tree endowment, scattered in roadside, park, and public and semi-public grounds. Based mainly on age, 384 outstanding trees of 25 species were officially designated as heritage specimens. They were evaluated in the field for tree dimensions and habitat types to establish landscape-ecological impacts and spatial differentiation by districts and landuses. To aid the analysis, new quantitative indices were developed, namely landscape-ecological value (LEV), biomass–landscape congruence (BLC), and species spatial differentiation (SSD), respectively, for species presence, abundance, fidelity and clustering. Cultivated natives and five common species dominated heritage trees, accompanied by 11 rare and 9 single ones. Comparisons between the urban- and the heritage-tree populations, and between the LEV of individual species, indicated the uniqueness of heritage species composition and relative landscape-ecological contributions of species groups. Tree count, LEV and species diversity increased markedly with district age, culminating in the second oldest district and then declined somewhat in the oldest; species richness peaked in the mature district and dropped in the old and oldest. Older districts had a narrow range of similarly stressful habitats accommodating mainly inherited old trees; mature districts had more diversified habitats and a dual provenance of inheritance plus recent recruits; young districts had few of both types. Stressful roadside landuse was dominated by tree count, but it was poor in species diversity and richness, and had a rather monotonous native-foliage character. Park provided ample opportunities for a complex species cohort of disparate geographical origin, dimension, age, and amenity function, but its species diversity fell short of expectations. The public and semi-public grounds harboured mainly common species except religious grounds which had higher species diversity and some notably large and unique trees. BLC and SSD results echoed the differential operation of environmental and human influences on tree biomass, configuration and landscape impacts, resulting in notable variations between districts and landuses. The management implications of the results and prognosis for the future of urban heritage trees were explored with reference to Guangzhou and other cities. [Copyright &y& Elsevier]

The recent fast pace of urbanization in China and other developing countries has exerted pressure on urban trees, which constitute a key urban environmental asset. The most outstanding trees should be treated as natural-cum-cultural heritage. Guangzhou City’s growth has threatened its rich urban-tree endowment, a diversified assemblage of 200,000 trees represented by 254 species and located in three major habitats: roadside, park, and institutional grounds. Mainly based on age and performance, 348 trees were officially designated as heritage specimens. They were evaluated in the field for tree dimensions, habitat, performance, and landscape contribution, to establish enhanced conservation and management strategies. With only 25 species, heritage trees were dominated by five cultivated natives and encompass some of the city’s rare species; some common urban-forest species were not represented. Older districts and roadside habitats, despite their compact town plan and limited growing space, had the largest tree dimensions and largest share of heritage trees. Many heritage trees were large with long life expectancy and the potential for biomass expansion, and had pivotal cityscape impacts where they occur. Old neighborhoods, traditional haven for the arborescent treasure, are being changed by construction activities and periodic typhoon and windstorm damages. Increasing development density could degrade the heritage trees and their growing space, and reduce tree quality and life span. Upgrading the statutory-administrative systems and arboricultural care can enhance long-term survival of the precious natural-cum-cultural heritage. The experience of Guangzhou in identifying and preserving its high-quality urban trees can provide management strategies for other cities. [ABSTRACT FROM AUTHOR]

Urban trees are under unprecedented pressure and competition worldwide with other land uses. Homestead windbreaks in urban areas are an important part of urban forests because of their proximity to settlements. To aid in the conservation of old-growth homestead trees in the urban setting on Ryukyu Archipelago, Japan, this article surveys the dimensions and spatial distribution of century-old trees planted as windbreaks along homestead borderlines on Ishigaki Island in the Ryukyu Archipelago and the historical change caused by urban sprawl. The homesteads studied in this article do not match the scale of a traditional Western context and usually consist of an area of less than 200 square meters on Okinawa. A combined approach consisting of field surveys and the study of aerial photos was applied to identify changes in spatial distribution of tree lines surrounding the houses in 1945, 1972 and the present. We measured the dimensions of 1659 Fukugi trees with a minimum diameter at breast height (DBH) of 5 cm. The mean tree height, mean DBH and mean estimated tree age were 7.3 m, 26.9 cm and 107.5 years, respectively. Homestead trees are not only useful as windbreaks, timber sources and musical instruments, but have also been historically resilient in the face of strong typhoons and catastrophic tsunamis in the region. Over 60% of the surveyed trees were planted on the east and north sides of homesteads as protection from typhoons and monsoonal winds in the winter. In addition to G. subelliptica, other tree species, namely Podocarpus macrophyllus and Diospyros egbert-walkeri, have been commonly used as homestead windbreaks. However, homestead windbreaks in highly urbanized regions are generally declining and have experienced fragmentation, lower tree density and shorter tree height than those in rural areas. Because of the small number of trees older than 200 years, we assume that high urbanization has jeopardized old-growth trees. The demand for settlement land dramatically increases as the population increases and household-size decreases, creating more households. Therefore, a conservation project involving multiple stakeholders must be developed to conserve old-growth trees in urban settings. [ABSTRACT FROM AUTHOR]