CY Jim
Education University of Hong Kong, Department of Social Science, Faculty Member
- Researcher on nature in cities.edit
Resettlement residential areas (RRAs) are a unique product of China’s urbanisation process. Their greening environment is critical to the quality of life and liveable green neighbourhood of the displaced farmers. Our study aimed to (1)... more
Resettlement residential areas (RRAs) are a unique product of China’s urbanisation process. Their greening environment is critical to the quality of life and liveable green neighbourhood of the displaced farmers. Our study aimed to (1) interpret the species composition of the landscape trees and their contributions to urban biodiversity in RRAs, and (2) elucidate the structural changes in the tree composition in the last 20 years. Twenty selected RRAs in Changzhou, Jiangsu Province, China, were divided into three categories by completion year. We assessed tree species composition, floristic diversity, tree dimensions, importance value, RRA characteristics, and greening management. The sampled sites accommodated 741 stems and 52 species belonging to 25 families. The three most abundant species were Cinnamomum camphora, Osmanthus fragrans, and Magnolia grandiflora, constituting 45.75% of all trees. The importance values revealed a changing tree planting pattern over time, with persist...
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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... more
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.
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Context Quantitative information regarding tree species-specific size is an essential tool for landscape planning. It reflects tree-environment and human–environment interactions in the urban landscape. The effects of habitat types on... more
Context Quantitative information regarding tree species-specific size is an essential tool for landscape planning. It reflects tree-environment and human–environment interactions in the urban landscape. The effects of habitat types on tree allometry have seldom been evaluated. Objectives Firstly, to derive size-related information of common urban tree species in Hong Kong. Secondly, to evaluate the effects of habitat types on tree allometry. Methods A database of 28,622 trees was established by a field assessment. The allometric relationships (DBH-height and DBH-crown width relationships), by both OLS regression and quantile regression, and maximum size of 30 common urban tree species, and the effects of five main habitat types on tree allometry were determined. Species were assigned to groups according to dimensional traits by cluster analysis. Results In general, the allometric relationships of height and crown width to DBH were significant and varied among species. The wide prediction intervals of the OLS regression indicated the high uncertainty of allometric relationships in our region. The 99th percentile crown width of most species reached 10 m, hinting the general failure of most habitats to meet the planting space requirement. Only two large-stature species have narrow crowns. Habitat types posed significant but small species-specific effects on tree allometry. Roadside tree pit was a particularly stressful environment. Conclusions Our findings can act as a reference for landscape planning and management in Hong Kong and nearby cities, including species growth space requirement and habitat limitations. However, prediction of height or crown width from DBH must be carefully interpreted in our city.
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Many cities advocate retrofitting green roofs and green walls (GRGW) to create additional green areas, especially in cramped urban areas. Yet, worldwide, only a handful of studies have evaluated the public views towards the benefits and... more
Many cities advocate retrofitting green roofs and green walls (GRGW) to create additional green areas, especially in cramped urban areas. Yet, worldwide, only a handful of studies have evaluated the public views towards the benefits and negative issues and promotion policies of this innovative greening option. To address this gap in the literature, we conducted a survey (N = 500) of residents’ opinions towards GRGW in Tokyo, a city with mandatory installation of GRGW for almost two decades. Respondents mostly agreed with the contribution of GRGW to thermal comfort, air quality, and cityscape but weakly endorsed other potential benefits. High costs as well as mosquitoes and plant litter nuisances were the most recognized negative issues. Mandatory installation was the least preferred promotion policy. Instead, respondents expected installation on public buildings and provision of installation guidance. Respondents predominantly held a “moderate” view towards both the benefits and negative issues, showing indifferent attitudes towards GRGW. Income level and housing type shaped the overall perceptions, whereas age, sex, and current living environment influenced perceptions of individual aspects. Our findings signified a need for a bottom-up strategy to heighten public awareness for the advanced development of GRGW to complement and prime the top-down mandatory installation policy.
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Abstract. Trees on buildings sites are routinely damaged or felled in Hong Kong due to negligence and lax control. In an unprecidented move, the government required the developer of a large well-wooded lot to retain one large Chinese... more
Abstract. Trees on buildings sites are routinely damaged or felled in Hong Kong due to negligence and lax control. In an unprecidented move, the government required the developer of a large well-wooded lot to retain one large Chinese Banyan (Fiscus microcarpa) tree and take necessary measures to en-sure its long-term survival. The size, fine condition, species rarity, longevity and setting justify its preservation. Great costs (about US$120,000) was needed mainly to construct a 18 m diameter and 10m deep reinforced concrete planter in site above five stories of shops and carparks. Routine ar-boricultural inputs, such as phased pruning of crown and roots, installation of aeration and irrigation facilities, and fer-tilization, are prescribed. Special precautions, including regular monitoring of watering and fertilization to minimize risks of physiological stresses, are justified in view of the costly
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Recent rapid urbanization has rendered outdoor space a key quality-of-life factor, yet walkability studies especially in hot-humid climates have seldom considered human biometeorology. This site-level study investigated microclimatic... more
Recent rapid urbanization has rendered outdoor space a key quality-of-life factor, yet walkability studies especially in hot-humid climates have seldom considered human biometeorology. This site-level study investigated microclimatic functions of an overhead structure in improving walkability, and identified biometeorology-related factors influencing pedestrian behaviour. A walkway with overhead tinted glass cover, demarcated into sunny zone and shaded zone, was equipped with hanging aluminium fins. Human thermal sensation was approximated by physiologically equivalent temperature (PET) and universal thermal climate index (UTCI), both closely related to global solar radiation and black-globe temperature. Pedestrian flow was tallied by demographic factors to assess the choice between shaded or sunny zones. Compared with sunny zone, shaded zone slashed maximum global solar radiation by 432 W/m 2 in full effect to achieve 90% solar radiation reduction. The maximum cooling in air and black-globe temperatures reached 0.8 °C and 6.1 °C respectively. The overhead structure imposed minimal effect on wind field in both zones. Contrast in maximum PET and UTCI between the two zones reached 8.2 °C and 5.3 °C respectively. In shaded zone, the dominant biometeorological condition was moderate heat stress or slightly warm sensation in contrast to strong heat stress or warm sensation in sunny zone. An overall preference for shaded zone was detected. Pedestrian gender and age, namely female and elderly, were significantly associated with shaded zone preference. The findings could inspire a biometeorological perspective in understanding walking behaviour and pedestrian-friendly facilities. Biometeorological-sensitive design of artificial shade could improve walkability in urban environment that increasingly demands climate change proofing.
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Selecting suitable species to enhance ecological functions is crucial for improvements in the planning and design of roof greening and in maintaining sustainable urban development, especially in rapidly urbanized areas. Assisted by field... more
Selecting suitable species to enhance ecological functions is crucial for improvements in the planning and design of roof greening and in maintaining sustainable urban development, especially in rapidly urbanized areas. Assisted by field trips to enhance studies, the present project assessed the ecological functions of 207 plant species used for roof greening in Beijing based on their key functional traits. The results indicate that regulating, cultural, supplying, and supporting functions differed significantly among species and families in the study area. Rosaceae species have higher levels of overall ecological functions than other species, and a large number of Compositae species have lower-level functions. Compared to other families, Araliaceae and Nyctaginaceae have higher mean values of cultural and supporting functions and the highest mean overall function value of 37. Ulmaceae, Sapindaceae, Ginkgoaceae, Berberidaceae, and Aceraceae have higher mean regulating, cultural, sup...
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Abstract A census of all existing roadside trees in urban Hong Kong was implemented to collect comprehensive information on site characteristics, growing space, tree structure, and tree defects and disorders. The survey methodology,... more
Abstract A census of all existing roadside trees in urban Hong Kong was implemented to collect comprehensive information on site characteristics, growing space, tree structure, and tree defects and disorders. The survey methodology, emphasizing data quality, uniformity, ...
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The changing mode of urban development through time can bring a varied landscape mosaic accompanied by spatial-temporal differentiation of urban vegetation. Hong Kong as an ultra-compact city generates intense interactions between trees... more
The changing mode of urban development through time can bring a varied landscape mosaic accompanied by spatial-temporal differentiation of urban vegetation. Hong Kong as an ultra-compact city generates intense interactions between trees and urban fabric to highlight urbanization effects on tree communities. The study areas cover public housing estates which accommodate about half of the 7.26 million population. Thirteen site factors related to estate, landform and habitat traits were measured or computed as surrogate urbanization effects. Species composition and diversity of tree communities in 102 estates were assessed by field surveys, including four estate groups: older or newer ones situated respectively in urban core or new towns. They contain 48,823 trees belonging to 232 species with heavy exotic representation. Total tree density and native tree density in newer estates were significantly higher than older ones. Differences in species richness and diversity and native species richness between older and newer estates were not significant, expressing to a certain extent the floristic-homogenization phenomenon. Multi-response Permutation Procedures (MRPP) results showed significant difference in species composition between older and newer estates, which could be explained by variations in development age, density, town plan and pre-urbanization land cover. Nonmetric Multidimensional Scaling (NMDS) results found tree distribution patterns in four estate groups strongly associated with estate area, open space area, estate population, estate age, Shannon index (H′) at planting strip and tree pit, and tree site quality index. Urban-forest management could be improved by adopting more native species and providing high-quality and spacious planting sites to accommodate more and larger trees. The research methods and findings could be used by policy makers and planners in similar large and developing cities to evaluate, design, maintain and enhance urban biodiversity.
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Urban trees, as prominent and pertinent landscape elements of cities, are increasingly studied by both practitioners and academics. Trees in Chinese cities have hitherto received little detailed analysis from the viewpoint of urban... more
Urban trees, as prominent and pertinent landscape elements of cities, are increasingly studied by both practitioners and academics. Trees in Chinese cities have hitherto received little detailed analysis from the viewpoint of urban forestry or landscape analysis. This study attempts a comprehensive evaluation of the tree population in Nanjing, focusing on the association between urban development and treescape attributes. Six
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Research Interests: Environmental Science, Energy Conservation, Power Plant, Soil moisture, Evapotranspiration, and 15 moreAir Conditioning, Green Roof, Energy Saving, Passive Cooling, Heat Flux, Relative Humidity, Thermal Performance, Solar radiation, Forestry Sciences, Air Temperature, Wind Speed, Roof, Heat Loss, surface temperature, and CO Emission
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Research Interests: Engineering, Landscape Ecology, Environmental Management, Ecology, China, and 15 moreLandscape, Urban Development, Network, Planning, Environmental Sciences, Urban form, Case Study, Open Space, Chine, Environmental quality, High Density Concrete, Urban Landscape and Planning, Environmental benefit, urban expansion, and High density
Research Interests: Engineering, Geography, Public Opinion, Natural Resources, Outdoor Recreation, and 15 moreChina, Environmental Sciences, Far East, Face to Face, Contingent valuation, Chine, Cost Benefit Analysis, Natural Capital, Elsevier, Cluster Sampling, Ordered Probit Model, Contingent Valuation Method, Age Groups, Recreational Activity, and Payment Cards
Research Interests: Engineering, Geography, Information Management, Urban Forestry, Urban Ecology, and 15 moreEnvironmental Sciences, Rare species, Nature Conservation, Indicator species, Species Diversity, Species Richness, Urban Green Space, Spatial Pattern, Green Space, Urban Forest, Ecosystem service, Statistical Test, Elsevier, Urban Park, and Tree Species
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ABSTRACT Intensively urbanized Hong Kong has a degraded countryside envelope with 170 years of afforestation history. This study assessed seedling quantity, species composition, native-exotic relativity, and native ecological traits in 30... more
ABSTRACT Intensively urbanized Hong Kong has a degraded countryside envelope with 170 years of afforestation history. This study assessed seedling quantity, species composition, native-exotic relativity, and native ecological traits in 30 years. Data were analysed by cluster analysis, two-way indicator species analysis (TWINSPAN), and principal component analysis (PCA). The plantations received 16.54 million seedlings from 209 species. Seedling profile skewed towards 142 native species (67.9%) and 9.49 million exotic seedlings (57.4%). The dominant species group had three exotic species each with >1 million seedlings. The abundant group of 27 species had contained 19 natives associated with main primary forest components. The 179 species in frequent and rare groups denoted changing and diverse species selection. Analysis of start and truncation times found 50% of natives with ascending trend and 33% of exotics with descending trend. Aggregate ecological value of natives increased progressively. TWINSPAN classified native species into two groups with signature characteristics. PCA revealed scattered distribution of natives by adoption trend, start time, truncation time, and ecological value. Ecological restoration of synergistic-mutualistic associations between native plants and wildlife has gained importance. Potential pioneer and enrichment-planting arboreal species were identified to sustain the afforestation programme. Hong Kong has a rich vascular flora with about 390 native tree species, implying that around 250 native tree species had never been used in afforestation. Large-scale planting trials should be conducted to further refine species choice in future afforestation. The findings could inform afforestation and conservation efforts in Hong Kong and other degraded tropical lands.
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... [20] E. Alexandri, P. Jones, Developing a one-dimensional heat and mass transfer algorithm for describing the effect of green roofs on the built environment: Comparison with experimental results. Building and Environment 42 (2007)... more
... [20] E. Alexandri, P. Jones, Developing a one-dimensional heat and mass transfer algorithm for describing the effect of green roofs on the built environment: Comparison with experimental results. Building and Environment 42 (2007) 2835-2849. ...
Research Interests: Engineering, Environmental Science, Modeling, Comparative Study, Medicine, and 15 moreSeasonality, Evaporative Cooling, Thermal Performance, Lancet, Temperature measurement, Thermal Analysis, Environmental Conditions, Thermal Insulation, Heat Diffusion, Porous Medium, Specific Heat, Abiotic Factor, Theoretical Model, Environmental Problem, and The Lancet
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Green roof, an increasingly common constituent of urban green infrastructure, can provide multiple ecosystem services and mitigate climate-change and urban-heat-island challenges. Its adoption has been beset by a longstanding... more
Green roof, an increasingly common constituent of urban green infrastructure, can provide multiple ecosystem services and mitigate climate-change and urban-heat-island challenges. Its adoption has been beset by a longstanding preconception of attracting urban pests like mosquitoes. As more cities may become vulnerable to emerging and re-emerging mosquito-borne infectious diseases, the knowledge gap needs to be filled. This study gauges the habitat preference of vector mosquitoes for extensive green roofs vis-à-vis positive and negative control sites in an urban setting. Seven sites in a university campus were selected to represent three experimental treatments: green roofs (GR), ground-level blue-green spaces as positive controls (PC), and bare roofs as negative controls (NC). Mosquito-trapping devices were deployed for a year from March 2015 to 2016. Human-biting mosquito species known to transmit infectious diseases in the region were identified and recorded as target species. Generalized linear models evaluated the effects of site type, season, and weather on vector-mosquito abundance. Our model revealed site type as a significant predictor of vector mosquito abundance, with considerably more vector mosquitoes captured in PC than in GR and NC. Vector abundance was higher in NC than in GR, attributed to the occasional presence of water pools in depressions of roofing membrane after rainfall. Our data also demonstrated seasonal differences in abundance. Weather variables were evaluated to assess human-vector contact risks under different weather conditions. Culex quinquefasciatus, a competent vector of diseases including lymphatic filariasis and West Nile fever, could be the most adaptable species. Our analysis demonstrates that green roofs are not particularly preferred by local vector mosquitoes compared to bare roofs and other urban spaces in a humid subtropical setting. The findings call for a better understanding of vector ecology in diverse urban landscapes to improve disease control efficacy amidst surging urbanization and changing climate.
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A compact city is a special urban form with inherent physical, social, and institutional constraints on greenery that obstruct the achievement of sustainability. In this study, Hong Kong is used as a case to assess the constraints and... more
A compact city is a special urban form with inherent physical, social, and institutional constraints on greenery that obstruct the achievement of sustainability. In this study, Hong Kong is used as a case to assess the constraints and challenges related to urban green spaces (UGS) development in compact cities. Strategies to overcome these obstacles and improve the UGS conditions are developed. Opportunities to implement the strategies are then evaluated. Because compact cities have extremely limited space allocated for UGS on the ground level, strategies to optimize the layouts of green spaces and seek additional spaces above or below the ground level, such as vertical green surfaces or structures, green roofs, and podiums, are possible solutions. Measures to implement the strategies are summarized as (1) reorganizing the departments and offices related to UGS and clarifying their individual responsibilities to increase their efficiency; (2) encouraging citizen participation; (3) establishing proper legal basis; (4) forming a comparatively connected comprehensive green network of green sources and green sinks with ground-level green spaces, skyscraper farms, and sky gardens, all with optimal layouts; (5) maintaining and repairing UGS after construction; and (6) selecting species of plants that will thrive in specific green spaces. The compact form of Hong Kong provides many chances to implement these strategies. The study increases understanding of the critical factors behind the success or failure of UGS develop- ment in one of the most compact cities in the world and provides suggestions for strategic and policy-related measures for the provision and management of UGS in other congested areas. DOI: 10.1061/(ASCE)UP.1943-5444.0000076. © 2012 American Society of Civil Engineers.
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Research Interests: Mechanical Engineering, Civil Engineering, Energy, China, Sensitivity Analysis, and 15 morePergamon, Solar Energy, Public Housing, Evapotranspiration, Energy Saving, Energy Balance, Passive Cooling, Heat Flux, Chine, Energy efficient, Interdisciplinary Engineering, Heat Dissipation, Soil Water, Remote Sensing Image, and Latent Heat
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Surveys of urban forests in the compact city environment of Hong Kong were initiated in 1985 and regularly updated thereafter. Roadside trees were evaluated first in a tree census and reported in this article followed by urban parks,... more
Surveys of urban forests in the compact city environment of Hong Kong were initiated in 1985 and regularly updated thereafter. Roadside trees were evaluated first in a tree census and reported in this article followed by urban parks, public housing estates, and special habitats such as old stone walls or special specimens such as heritage trees. The survey method aimed at collecting comprehensive data to echo both tree conditions and tree–environmental interactions. Detailed information was gleaned, with the help of well-trained assistants, on tree sites, tree growing space, tree structure, and tree defects and disorders. A field record form was designed, pilot-tested, and refined to solicit responses to multiple choices or direct measurements to minimize subjectivity and errors in data recording and entry. The study also identified potential planting sites, registering suitability for tree growth, site characteristics, and dimensions. Data fields were designed to be quantitative or...
Research Interests: Geography, Spatial Analysis, Methodology, Community Ecology, Statistical Analysis, and 15 moreEcology, Biodiversity, Survey Methods, Growth, Interactions, Arboriculture, Surveys, Measurement, Forests, Ornamental plants, Species Diversity, Habitats, Forestry Sciences, Large Scale, and Horticultural production
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Abstract Green roofs contribute notably to green building and sustainable city goals. Most studies focused on summer cooling and energy-saving benefits, with little attention on winter warming effect. This study evaluated contributions of... more
Abstract Green roofs contribute notably to green building and sustainable city goals. Most studies focused on summer cooling and energy-saving benefits, with little attention on winter warming effect. This study evaluated contributions of the soil component to winter warming with reference to the thickness and moisture content. In subtropical Wuyishan city, Fujian Province, China, we built three houses as experimental green-roof plots. We adjusted soil thickness, measured moisture content, and monitored their impacts on roof outer surface temperature (ROST) in winter. We designated measured outdoor temperature, relative humidity, solar radiation, wind speed, soil thickness and soil moisture content as independent variables, and ROST as dependent variable. The empirical data were enlisted to establish a neural-network prediction model in conjunction with a genetic algorithm to optimize parameter thresholds and weights. The numerical model successfully predicted winter ROST at different combinations of soil thickness and moisture content and identified the best value for energy-saving performance. The model predicted that the maximum ROST of 13.5 °C was achieved at 20 cm soil thickness and 3.9 % moisture content. The choice of deciduous or evergreen plants could fine-tune soil moisture requirement and improve warming service. The study demonstrated the feasibility of optimizing the green-roof design by adjusting controllable soil variables. The neural-network model could reliably predict ROST under different soil conditions to inform design and management.
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Abstract Thermal modifications by a 1.5 m deep pond on adjacent lawn microclimate on sunny, cloudy, overcast and rainy summer days were investigated in subtropical Hong Kong. Microclimatic parameters at a pondside lawn were monitored and... more
Abstract Thermal modifications by a 1.5 m deep pond on adjacent lawn microclimate on sunny, cloudy, overcast and rainy summer days were investigated in subtropical Hong Kong. Microclimatic parameters at a pondside lawn were monitored and compared to an open lawn and a concrete rooftop (Control), with focus on Universal Thermal Climate Index (UTCI) to investigate thermal comfort. The cooling capability of the studied pond has been ascertained – pondside lawn registered the lowest air temperatures (Ta) in most weather conditions, and mean Ta of sunny daytime at pondside lawn was 0.7 °C cooler than open lawn. Compared to Control, UTCI calculations indicated hotter mean daytime conditions at pondside lawn (−2.3 °C) than open lawn (−3.5 °C) on sunny day. Despite the pond’s ability to lower Ta, the lack of pondside tree shading created worse human heat-stress scenarios than open lawn. Cloudy day displayed lower heat-stress levels, but pondside lawn still recorded the highest frequency of strong heat stress (83.6%). To synergistically resolve the thermal-stress problems and transform pond-induced microclimatic cooling into physiological cooling for humans, deeper and more dynamic waterbodies could be incorporated alongside pondside tree shading and natural surfaces in urban park design.