Predicting suitable habitat for the endangered tree Ormosia microphylla in China.

Climate change has significantly influenced the growth and distribution of plant species, particularly those with a narrow ecological niche. Understanding climate change impacts on the distribution and spatial pattern of endangered species can improve conservation strategies. The MaxEnt model is widely applied to predict species distribution and environmental tolerance based on occurrence data. This study investigated the suitable habitats of the endangered Ormosia microphylla in China and evaluated the importance of bioclimatic factors in shaping its distribution. Occurrence data and environmental variables were gleaned to construct the MaxEnt model, and the resulting suitable habitat maps were evaluated for accuracy. The results showed that the MaxEnt model had an excellent simulation quality (AUC = 0.962). The major environmental factors predicting the current distribution of O. microphylla were the mean diurnal range (bio2) and precipitation of the driest month (bio14). The current core potential distribution areas were concentrated in Guangxi, Fujian, Guizhou, Guangdong, and Hunan provinces in south China, demonstrating significant differences in their distribution areas. Our findings contribute to developing effective conservation and management measures for O. microphylla, addressing the critical need for reliable prediction of unfavorable impacts on the potential suitable habitats of the endangered species.

Herbaceous ornamental plants with conspicuous aesthetic traits contribute to plant invasion risk in subtropical urban parks.

Global ornamental horticulture is a major pathway for plant invasions, while urban parks are key areas for introducing non-native ornamental plants. To react appropriately to the challenges (e.g., biological invasion issues) and opportunities (e.g., urban ecosystem services) of herbaceous ornamentals in urban parks, we conducted a comprehensive invasive risk assessment in 363 urban parks in Chongqing, a subtropical city in China. The results found more than 1/3 of the 119 non-native species recorded in urban parks had a high invasion risk, and more than five species had potential invasion risk in 96.29% of the study area, indicating herbaceous ornamentals in urban parks are potentially a pool of invasive species that deserves attention. Moreover, humans have chosen herbaceous ornamentals with more aesthetic characteristics in urban parks, where exotic species were more prominent than native species in floral traits, such as more conspicuous flowers and longer flowering periods. The findings can inform urban plant management, provide an integrated approach to assessing herbaceous ornamentals' invasion risk, and offer insights into understanding the filtering effects of human aesthetic preferences.

Human activities and species biological traits drive the long-term persistence of old trees in human-dominated landscapes.

Old trees have many ecological and socio-cultural values. However, knowledge of the factors influencing their long-term persistence in human-dominated landscapes is limited. Here, using an extensive database (nearly 1.8 million individual old trees belonging to 1,580 species) from China, we identified which species were most likely to persist as old trees in human-dominated landscapes and where they were most likely to occur. We found that species with greater potential height, smaller leaf size and diverse human utilization attributes had the highest probability of long-term persistence. The persistence probabilities of human-associated species (taxa with diverse human utilization attributes) were relatively high in intensively cultivated areas. Conversely, the persistence probabilities of spontaneous species (taxa with no human utilization attributes and which are not cultivated) were relatively high in mountainous areas or regions inhabited by ethnic minorities. The distinctly different geographic patterns of persistence probabilities of the two groups of species were related to their dissimilar responses to heterogeneous human activities and site conditions. A small number of human-associated species dominated the current cohort of old trees, while most spontaneous species were rare and endemic. Our study revealed the potential impacts of human activities on the long-term persistence of trees and the associated shifts in species composition in human-dominated landscapes.

Environmental Factors Driving the Spatial Distribution Pattern of Venerable Trees in Sichuan Province, China.

Venerable trees are important natural resources and cultural heritage, offering historical, ecological, social and economic value. However, global warming and anthropogenic activities have threatened their welfare and survival. A comprehensive understanding of their current and future spatial patterns, vis-á-vis environmental conditions, can inform the co-management of sustainable resource use and conservation. We employed the existing spatial occurrence data and environmental variables (bioclimate and elevation) to simulate the optimal habitats for venerable trees in China's Sichuan Province. We evaluated the current and future climate scenarios of 2100 with double CO2 concentration. The BIOCLIM and QGIS spatial analyses assessed the primary factors of geographical distribution. The results identified 10,720 venerable trees from 123 species, 81 genera and 42 families. Cupressus funebris dominated, with the maximum importance value, followed by Ginkgo biloba, Ficus virens var. sublanceolata, and Phoebe zhennan. The elevation distribution of tree abundance and species richness demonstrated a unimodal pattern, skewing to the low-elevation end, with a concentration in the 600-1500 m low-medium altitude. The majority of trees and excellent habitats were found in eastern Sichuan with a less harsh terrain and climate. The bio3 (isothermality) and bio7 (temperature annual range) factors significantly influenced tree occurrence. Temperature imposed a greater effect on distribution than moisture under the current climate scenario. For the future climate-change scenario, the suitable habitats were predicted to maintain an overall stable pattern, with largely contiguous expansions of better habitats. However, climate warming would shrink the excellent habitats on the plains. The findings can inform strategies and guidelines for venerable-tree conservation in Sichuan. Furthermore, vulnerable areas could be identified. The future range expansion sites could be enlisted to cultivate new trees to replenish the venerable-tree pool. Habitat patches that remain sustainable could provide refugia with the potential for protected-area designation.

Characterizing composition profile and diversity patterns of spontaneous urban plants across China's major cities.

Spontaneous urban plants (SUPs) constitute an important component of urban vegetation, but they have received less attention in urban biodiversity and ecological research, especially at the regional scale. We comprehensively reviewed the occurrence records of SUPs in 59 major cities across China's geographical regions. We systematically analyzed floristic composition profiles and diversity patterns of SUPs at the regional scale and explored their influencing factors. The study identified 1211 SUP species through an extensive search of existing field research studies and fieldwork. The species composition pattern of SUPs, displaying a spatial association with climatic zones, was mainly affected by climatic factors and also anthropogenic factors. At different geographic scales, the life-form characteristics revealed some patterns, with more diverse perennials at the regional scale. The abundance of SUPs and the high proportion of native species suggested that limited urban habitats can still contribute to the enrichment and accumulation of urban biodiversity. However, in the context of globalization, continual species exchanges between neighboring regions at different scales may significantly exacerbate urban-biota homogenization. In conclusion, our study provided a regional-scale case of a synoptic SUP profile. The results furnished a scientific basis for understanding the general patterns of SUPs. The findings could inform sustainable solutions for urban ecological planning and management of spontaneous nature in cities.

Public Perceptions of Green Roofs and Green Walls in Tokyo, Japan: A Call to Heighten Awareness.

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.

Climate change fostered cultural dynamics of human resilience in Europe in the past 2500 years.

Humans possess limited knowledge on what generated cultural dynamics to strengthen human resilience to overcome climate-induced stresses. Although the highly developed mental ability of humans could have enabled significant human resilience in history, no study has empirically explained or has even scientifically confirmed how and when such dynamics arose. To fill the current research gap, this study therefore explores the associations among climatic conditions, the evolutional dynamics of human thinkers and their thoughts, and human ecological-socioeconomic conditions in the past 2500 years in Europe. Results from quantitative modellings and causal analyses confirm that climatic-ecological stresses led to human ecological-socioeconomic crises, and thereby dramatically increased twice of the thinkers' number and their thoughts' impact across different philosophies in truth, knowledge, and ethics for adaptation at multi-decadal to centennial temporal scales, especially in spirituality oriented mentality. The process of the stress-generated cultural dynamics displays some similarities with the stress-induced mutagenesis in organism evolution. Ultimately, climatic-ecological stresses prompt the escalation in the number of thinkers and impacts of their thoughts and flourishing of philosophy. Such stress-regenerated cultural dynamics imply that the current climate change threat may stimulate another thriving phase of cultural selection and lift humans to the next homeostatic plateau of civilization. Findings also extend the cognate scope of psychological, sociological, and civilization studies.

Improving street walkability: Biometeorological assessment of artificial-partial shade structures in summer sunny conditions.

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/m2 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.

Urban woodland on intensive green roof improved outdoor thermal comfort in subtropical summer.

Global climate change and urban heat island effect have jointly threatened human thermal comfort in cities. Intensive green roof (IGR) could supplement urban green space to alleviate thermal comfort. Aiming at examining the impact of IGR on the thermal comfort of its users, Universal Thermal Climate Index (UTCI) and physiological equivalent temperature (PET) were applied to assess effectiveness of IGR in improving outdoor thermal comfort by IGR. Comprehensive microclimatic monitoring was conducted on urban woodland IGR and an adjacent control bare roof in humid-subtropical Hong Kong. Sunny days (n = 21) and cloudy days (n = 18) were selected from summer in 2016. Insolation, air, and surface temperatures were compared between the two roofs. UTCI and PET were computed for the daytime and nighttime period of each sampled day. On IGR, significantly higher environmental cooling was achieved during daytime in sunny weather, with mean surface and air cooling reaching 4.9 °C and 1.6 °C respectively. Woodland IGR successfully improved thermal sensation by cooling mean UTCI and PET by 5.5 °C and 10.9 °C respectively during daytime in sunny scenario. Woodland IGR reduced the occurrence of extreme and very strong heat stress which struck the control bare roof. Recommendations on about thermal sensation were provided for building owners, town planners, and landscape architects.

Impacts of air conditioning on air quality in tiny homes in Hong Kong.

The risk of developing sick building syndrome is known to be higher in air-conditioned than naturally ventilated spaces. In Hong Kong, air conditioning (AC) is commonly used in homes to relieve summer heat stress. This study aims to assess the air quality impacts of AC in tiny homes called SDUs (sub-divided units). Poor ventilation and stronger heat stress in such informal housing could necessitate the use of AC. Predicted mean vote (PMV), CO, CO2, PM10, PM2.5 and VOCs were continuously monitored for 72 h in eight SDUs. PMV was ≥2 ('warm') in 75% of the SDUs at sleeping time (after 22:00), implying an 80% dissatisfaction among the occupants. During AC use, the mean concentrations of CO and CO2 increased from 220 to 905 µg/m3 (+312%) and from 920 to 1711 mg/m3 (+86%) respectively. The highest CO2 level (3758 mg/m3) was observed in a 3-person household (one more than other SDUs). The overall impacts on PM10 (+4%) and PM2.5 (+19%) were relatively insignificant. Reduced ventilation in air-conditioned homes facilitated the accumulation of VOCs (mean change: +22%). The findings could inform building design and modify AC usage practice to improve the indoor environment.

Do vegetated rooftops attract more mosquitoes? Monitoring disease vector abundance on urban green roofs.

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.

Come rain or shine? Public expectation on local weather change and differential effects on climate change attitude.

Tailored messages are instrumental to climate change communication. Information about the global threat can be 'localised' by demonstrating its linkage with local events. This research ascertains the relationship between climate change attitude and perception of local weather, based on a survey involving 800 Hong Kong citizens. Results indicate that concerns about climate change increase with expectations about the likelihood and impacts of local weather change. Climate change believers attend to all three types of adverse weather events, namely, temperature rises, tropical cyclones and prolonged rains. Climate scepticism, however, is not associated with expectation about prolonged rains. Differential spatial orientations are a possible reason. Global climate change is an unprecedented and distant threat, whereas local rain is a more familiar and localised weather event. Global climate change should be articulated in terms that respect local concerns. Localised framing may be particularly effective for engaging individuals holding positive views about climate change science.

Resident motivations and willingness-to-pay for urban biodiversity conservation in Guangzhou (China).

The monetary assessment of biodiversity measures the welfare damages brought by biodiversity losses and the cost-benefit analysis of conservation projects in a socio-economic context. The contingent valuation method could include motivational factors to strengthen economic analysis of nature conservation. This study analyzed Guangzhou residents' motivations and willingness-to-pay (WTP) for an urban biodiversity conservation program in the National Baiyun Mountain Scenic Area (BMSA). The peri-urban natural site, offering refuge to some endemic species, is under increasing development pressures for recreational and residential use. A questionnaire survey was conducted in the Guangzhou metropolitan area during June to October 2007. We interviewed face-to-face 720 stratified sampled households to probe residents' attitudes towards the city's environmental issues, motivations for urban nature conservation, and WTP for biodiversity conservation. Principal component analysis identified five motivational factors, including environmental benefit, ecological diversity, nature-culture interaction, landscape-recreation function, and intergenerational sustainability, which illustrated the general economic values of urban nature. Logistic regression was applied to predict the probability of people being willing to pay for the urban biodiversity conservation in BMSA. The significant predictors of WTP included household income and the factor nature-culture interaction. The median WTP estimated RMB149/household (about US$19.5/household) per year and an aggregate of RMB291 million (approximately US$38.2 million) annually to support the urban conservation project. Including public motivations into contingent valuation presents a promising approach to conduct cost-benefit analysis of public projects in China.

Assessing the ecosystem service of air pollutant removal by urban trees in Guangzhou (China).

In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Besides technical solutions to abate air pollution, urban vegetation is increasingly recognized as an alternative ameliorative method by removing some pollutants mainly through dry deposition process. This paper assesses the capability and monetary value of this ecosystem service in Guangzhou city in South China. The results indicated an annual removal of SO(2), NO(2) and total suspended particulates at about 312.03 Mg, and the benefits were valued at RMB90.19 thousand (US$1.00=RMB8.26). More removal was realized by recreational land use due to a higher tree cover. Higher concentration of pollutants in the dry winter months induced more removal. The lower cost of pollution abatement in China generated a relatively subdued monetary value of this environmental benefit in comparison with developed countries. Younger districts with more extensive urban trees stripped more pollutants from the air, and this capacity was anticipated to increase further as their trees gradually reach final dimensions and establish a greater tree cover. Tree cover and pollutant concentration constitute the main factors in pollutant removal by urban trees. The efficiency of atmospheric cleansing by trees in congested Chinese cities could be improved by planting more trees other than shrubs or grass, diversifying species composition and biomass structure, and providing sound green space management. The implications for greenery design were discussed with a view to maximizing this ecosystem service in Chinese cities and other developing metropolises.

Local responses to inundation and de-farming in the reservoir region of the three gorges project (China).

Large-scale infrastructural developments in rural areas often impose significant direct and indirect impacts on environment and people. The Three Gorges Project to dam the Yangtze River in China will create a huge reservoir, inundate farmlands and villages, and incur large-scale resettlement. The concurrent de-farming program to reforest marginal farmlands on steep slopes imposes additional stresses on local people. This study evaluates the ecological and economic adjustments in rural areas affected by both projects, and explores villagers' knowledge, attitudes, perceptions, and expectations vis-à-vis the drastic changes. Eleven villages in Yunyang County in Sichuan Province, stratified into three zones based on topography and agriculture, were assessed by field studies, questionnaire surveys, maps, satellite imagery, and census and government reports. Multiple regressions identified predictors for 17 dependent variables. Spatial variations in the difficult terrain imposed zone-differentiated agricultural constraints, ecological impacts, and human responses. The dominant farming population--mainly young adults working as migrant laborers in cities--has adopted some nonagricultural work to supplement incomes. Expected per-capita standardized farmland (SF) exceeded threshold SF, which surpasses existing SF. Motivations to reclaim more farmlands, de-farm marginal lands, and become migrant laborers were explained by different multiple-regression predictors. Reduction in farmland stock by inundation and de-farming, aggravated by unwillingness towards nonlocal resettlement, would impose ecological pressures and stimulate demands for nonfarming incomes. Common anticipation of better future income and occupation has been subdued by unfavorable feedbacks from early relocatees. Future environmental and landscape changes are hinged upon changing human responses. Government policies could be informed by research findings to match economic, ecological, and social realities.

Perception and attitude of residents toward urban green spaces in Guangzhou (China).

Fast economic and social changes in recent years in China have brought massive expansion, redevelopment, and restructuring of cities. These changes offer cities the opportunity to improve environmental quality through urban green spaces (UGSs) and to address the challenges of meeting community aspirations. This study explored peoples' minds concerning UGSs in Guangzhou city in south China in relation to the following: (1) knowledge and perception of 25 ecosystem services and 8 negative impacts; (2) attitude toward site condition and management; (3) expectation of landscape design; and (4) preference ranking of venues. A questionnaire was designed to solicit opinions from 340 respondents randomly chosen from residents living in the study area. The results indicated widespread recognition of ecosystem services and strong support of UGS programs. Negative responses were weakly expressed. Amelioration of urban microclimate and environmental quality were emphasized. Environmental functions stressed in publicity programs, together with aggravating environmental problems in the city, tended to focus respondents' attention on UGS benefits. Wildlife habitat, species conservation and other natural ecosystem services drew limited concerns. Awareness of economic benefits was very low. Visual-landscape contributions with strong preference for naturalistic design and recreational benefits were highlighted. Compared with other countries, Guangzhou residents were characterized by visual-scenic-recreation orientation and pragmatic-utilitarian perception of UGSs, reflecting underlying differences in the understanding of inherent ecosystem services of green spaces. Relevant UGS policies and practices could adopt the approaches of market survey, citizen participation, and precision planning in order to meet increasingly mature and refined demands. Citizens' understanding of high-order ecosystem services could be enhanced to encourage appreciation of nature and their associated benefits.

Formulaic expert method to integrate evaluation and valuation of heritage trees in compact city.

Urban trees serve important environmental, social and economic functions, but similar to other natural endowments they are not customarily depicted in monetary terms. The needs to augment protection, funding and community support for urban greening call for proper valuation. Heritage trees (HTs), the cream of urban-tree stock, deserve special attention. Existing assessment methods do not give justice to outstanding trees in compact cities deficient in high-caliber greenery, and to their social-cultural-historical importance. They artificially separate evaluation from valuation, which should be a natural progression from the former. Review of tree valuation methods suggested the formula approach to be more suitable than contingent valuation and hedonic pricing, and provided hints on their strengths and weaknesses. This study develops an alternative formulaic expert method (FEM) that integrates evaluation and valuation, maximizes objectivity, broadly encompasses the key tree, tree-environment and tree-human traits, and accords realistic monetary value to HTs. Six primary criteria (dimension, species, tree, condition, location, and outstanding consideration) branched into 45 secondary criteria, each allocated numerical marks. Each primary criterion was standardized to carry equal weight, and a tree's maximum aggregate score is capped at 100. A Monetary Assignment Factor (MAF) to consign dollar value to each score unit was derived from three-year average per m(2) sale price of medium-sized residential flats. The applicability of FEM was tested on selected HTs in compact Hong Kong. The aggregate score of a tree multiplied by MAF yielded monetary value, which was on average 66 times higher than the result from the commonly-adopted Council of Tree and Landscape Appraisers method. The computed tree values could be publicized together with multiple tree benefits to raise understanding and awareness and rally support to protect HTs. The property-linked FEM could be flexibly applied to other cities, especially to assess HTs in compact developing cities.

Floristics, performance and prognosis of historical trees in the urban forest of Guangzhou city (China).

Outstanding historical trees embedded in cities constitute pertinent environmental assets, yet they are widely threatened in third-world cities. Inadequate understanding of this valuable natural-cum-cultural heritage hinders proper conservation. A case study of Guangzhou in south China evaluated floristic composition, age profile and biomass structure of historical trees, assessed their performance in major habitats (institutional, park and roadside), and established a prognosis for future growth and management. The 348 historical trees examined belonged to only 25 species, vis-à-vis 254 trees in the entire urban forest, dominated by five species and native members. Roadside had more trees, followed by institutional and park, with merely the most common four species shared by all habitats. The limited commonality reflected tree-performance differentiation by habitats exerting selection pressure on species. The institutional growth-regime was more conducive to nurturing high-caliber specimens, whereas park is less capable. Individual species achievement by habitats, derived from tree-count ranking and relative-abundance indices, could inform species choice and tree conservation. Few trees exceeded 300 years of age in the millennium-old city, echoing a history of intense tree-city conflicts. Potential life-span, trunk and crown diameters indicated ample opportunities for further expansion of biomass and landscape impacts, which would be straitjacketed by the tightening urban fabric.

Monitoring the performance and decline of heritage trees in urban Hong Kong.

Urban trees in Hong Kong exist in stressful and harsh habitat conditions due mainly to the exceptionally high-density development mode. This study focuses on the cream of the urban tree stock, the heritage trees, which were selected according to five sets of stringent criteria: species, dimension, structure, condition, location, and special considerations. The study area covers the main urban core of the city. The loss of trees in two periods, 1993-1998 and 1999-2003, was monitored, with the predisposing and direct causes of damages ascertained as far as possible. Of the 380 heritage specimens, 54 trees were lost in the survey period. The main predisposing causes were injuries sustained in roadwork and construction activities, both related to root damage and soil disturbance. The principal direct causes were recent gradual decline and abrupt demise due to typhoon breakage. Three pairs of contributing variables registered statistically significant associations (chi(2) test), namely predisposing cause versus direct cause, tree growth form versus direct cause, and survey period versus direct cause. Principal component analysis identified three factors that explained 70% of the variance, namely tree form, tree stature, and growth environment. The main reasons for the high mortality were explored. The possible applications of the findings to improve tree protection and management were discussed in relation to the overall planning for meritorious greenery and green space especially in compact cities.

Evaluation of heritage trees for conservation and management in Guangzhou City (China).

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.