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Increasing the urban tree cover percentage (TCP) is widely recognized as an efficient way to mitigate the urban heat island effect. The cooling efficiency of urban trees can be either enhanced or attenuated on hotter days, depending on the physiological response of urban trees to rising ambient temperature. However, the response of urban trees' cooling efficiency to rising urban temperature remains poorly quantified for China's cities. In this study, we quantify the response of urban trees' cooling efficiency to rising urban temperature at noontime [∼1330 LT (local time), LT=UTC+8] in 17 summers (June, July, and August) from 2003–19 in 70 economically developed cities of China based on satellite observations. The results show that urban trees have stronger cooling efficiency with increasing temperature, suggesting additional cooling benefits provided by urban trees on hotter days. The enhanced cooling efficiency values of urban trees range from 0.002 to 0.055°C %−1 per 1°C increase in temperature across the selected cities, with larger values for the low-TCP-level cities. The response is also regulated by background temperature and precipitation, as the additional cooling benefit tends to be larger in warmer and wetter cities at the same TCP level. The positive response of urban trees' cooling efficiency to rising urban temperature is explained mainly by the stronger evapotranspiration of urban trees on hotter days. These results have important implications for alleviating urban heat risk by utilizing urban trees, particularly considering that extreme hot days are becoming more frequent in cities under global warming. [ABSTRACT FROM AUTHOR]

Introduction: Extreme weather becomes increasingly frequent and severe under climate change, causing unexpected damage to trees. Among them, sleet damage is particularly harmful to evergreen trees in subtropical area. Camphor trees (Cinnamomum camphora), as dominant street trees in central China, are prone to sleet damage, resulting in loss of valuable ecosystem functions. Methods: By measuring tree size characteristics of 118 camphor trees before and after a record-breaking sleet event in Wuhan, a mega-city in central China, we built allometric equations between size and volume of broken branches and used the random forest regression to model sleet damage to camphor trees. Results: We identified that larger trees with intermediate bole height suffered more than smaller trees with tall bole height from the sleet event. We estimated the volume of broken branches of a camphor tree with DBH at 35.0 cm as 106.4 dm3, equivalent to 55.3 kg biomass loss, from the sleet event. Discussion: We suggest that pruning the branches instead of topping the main stems of small camphor trees would reduce the sleet hazard. To mitigate the negative impacts of climate change, regular pruning should be practiced on street camphor trees to protect them from future heavy sleet events. [ABSTRACT FROM AUTHOR]

Due to the importance of trees in urban ecosystems, it is crucial to understand the distribution, prevalence, and intensity of parasitic mistletoe infection across urban landscapes. In this study, we aimed to understand how various tree-related factors (e.g., tree taxonomy, size, pruning history, nativity, foliage, density, and diversity) might influence mistletoe prevalence and infection intensity across a typical subtropical urban greenspace. We surveyed 6,012 trees representing 96 species, 76 genera, and 44 families across a large, urban university campus in a major Southwest Chinese city. In total, we found 353 mistletoe host trees (prevalence: 5.87%), largely concentrated on the eastern part of campus, partially due to the proximity of waterbodies and a large adjacent greenspace, as well as higher tree density. To understand how predictors affected the prevalence and intensity of mistletoe infection, we used a hurdle model fitting our zero-inflated count data. Four independent variables significantly affected the prevalence of mistletoe infestation, with three demonstrating positive correlations (crown width, tree density, and tree diversity). One variable (evergreen foliage) negatively correlated with mistletoe prevalence. However, only one factor was found to significantly affect mistletoe infection intensity (crown width, positively). Due to the variety of ecosystem services mistletoes provide, more studies are necessary to assess the impact of various mistletoe management strategies, especially on urban biodiversity. Highlights: Of 6,012 surveyed trees, 353 hosted mistletoes, but 50 of 96 species did not. Four tree-related factors affected mistletoe prevalence (3 positively/1 negatively). Only tree size (positively) affected infection intensity. [ABSTRACT FROM AUTHOR]

The Taihangshan-Yanshan region (TYR) is an important ecological barrier area for Beijing-Tianjin-Hebei, and the effectiveness of its ecological restoration and protection is of great significance to the ecological security pattern of North China. Based on the FVC data from 2000 to 2021, residual analysis, parametric optimal geodetector technique (OPGD) and multi-scale geographically weighted regression analysis (MGWR) were used to clarify the the multivariate driving mechanism of the evolution of FVC in the TYR. Results show that: (1) FVC changes in the TYR show a slowly fluctuating upward trend, with an average growth rate of 0.02/10a, and a spatial pattern of "high in the northwest and low in the southeast"; more than half of the FVC increased during the 22-year period. (2) The results of residual analysis showed that the effects of temperature and precipitation on FVC were very limited, and a considerable proportion (80.80% and 76.78%) of the improved and degraded areas were influenced by other factors. (3) The results of OPGD showed that the main influencing factors of the spatial differentiation of FVC included evapotranspiration, surface temperature, land use type, nighttime light intensity, soil type, and vegetation type (q > 0.2); The explanatory rates of the two-factor interactions were greater than those of the single factor, which showed either nonlinear enhancement or bifactorial enhancement, among which, the interaction of evapotranspiration with mean air and surface temperature has the strongest effect on the spatial and temporal evolution of FVC (q = 0.75). Surface temperature between 4.98 and 10.4 °C, evapotranspiration between 638 and 762 mm/a, and nighttime light between 1.96 and 7.78 lm/m2 favoured an increase in vegetation cover, and vegetation developed on lysimetric soils was more inclined to be of high cover. (4) The correlation between each variable and FVC showed different performance, GDP, elevation, slope and FVC showed significant positive correlation in most regions, while population size, urban population proportion, GDP proportion of primary and secondary industries, and nighttime light intensity all showed negative correlation with FVC to different degrees. The results can provide data for formulating regional environmental protection and restoration policies. [ABSTRACT FROM AUTHOR]

With increased atmospheric temperature, temperatures in the shade of trees in parks also increase, and people are faced with high temperature challenges. In this study, thermal comfort in the shade of the trees of an urban park during summer in China was assessed. The subjective responses of the respondents were recorded via questionnaires, and environment parameters were measured. The results show that the air temperature in the shade was 31.1 ± 3.0 °C during the day, and that it peaked at 36.9 °C; the globe temperature was 31.3 ± 3.1 °C, and it peaked at 40.1 ℃. Respondents' clothing insulation was 0.31 ± 0.08 clo, and the effect of clothing adjustment on thermal adaptation was limited. Thermal sensation is linearly related to standard effective temperature (SET), and the upper limit of 80% acceptable SET was 32.1 °C. At different temperature values, the proportion of expected airflow enhancement exceeded 50%. The respondents preferred a neutral-warm sensation. Moreover, there was an obvious thermal adaptation, with thermal history and psychological adaptation being the main factors affecting thermal comfort. This study confirmed the value of shade and provided us with guidance for park planning and design. [ABSTRACT FROM AUTHOR]

Exploring the impact of complex urban morphology on the urban heat island (UHI) effect is essential for sustainable environmental management and enhancing human well-being. This study explored the combined cooling effect of street canyon geometry and the surrounding built environment using a CatBoost model and the Shapley method. The findings indicated that in streets with low building height and density, a high proportion of sky and vegetation and a flatter skyline are conductive to mitigate UHI effect. In streets with high building height and density, a lower proportion of sky and vegetation, and a well-proportioned skyline, can effectively mitigate UHI effect. Regardless of the building density and height around the street, street trees are the optimal choice for greening construction and improvement of large and medium-sized cities in China, given their high controllability and the current urban stock background. Therefore, reasonable control and allocation of street trees can effectively adjust the street canyon geometry, providing suitable cooling strategies for streets with different surrounding built environments. This study proposed a method to mitigate the UHI effect through street canyon geometry, which can be extended to other high-density urban thermal environment studies and guide policymakers on street construction and urban design. [ABSTRACT FROM AUTHOR]

Green vegetation is one of the main objects of ecological environment restoration and protection, objectively reflecting the quality of regional ecological environments. Studying its spatial distribution characteristics is of great significance to the formulation of ecological environment restoration policies. Based on data on urban green vegetation in China from 2000 to 2022, this study attempts to analyze the destruction and protection patterns of urban green vegetation in China from the perspectives of total changes in green vegetation contraction and growth and spatial evolution characteristics and trends, and it explores the driving factors affecting the change in green vegetation area. The results show the following: (1) Green vegetation growth and contraction occurred alternately in China from 2000 to 2022. Vegetation contraction showed a "point–line–plane" evolution pattern, forming a contraction stage of point-like aggregation, linear series, and planar spread. Vegetation growth has always presented a frontal pattern. (2) The growth and contraction of green vegetation in China showed a north–south differentiation phenomenon. The vegetation contraction phenomenon spread in the Central Plains urban agglomeration and its surrounding areas and showed an expanding trend. The growth trend is obviously moving northward, mainly concentrated in Inner Mongolia, Ningxia, Gansu, Xinjiang, and other northern provinces, which also coincides with the key ecological restoration policies in northern China in recent years. (3) City scale, economic level, population scale, agro-industrial structure, and water resources content have significant effects on the spatial distribution of green vegetation. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is one of the limiting nutrients for plant growth and metabolism in terrestrial ecosystems. Numerous studies have explored the effects of N addition on the eco-physiological traits and biomass production of plants, but the underlying mechanism of how N deposition influences biomass allocation patterns remains controversial, especially for urban greening trees. A greenhouse experiment was conducted for 7 months, using two dominant tree species of urban streets in North China, including the coniferous tree species Pinus tabuliformis and the broadleaved tree Fraxinus chinensis, under three levels of N addition: ambient, low N addition, and high N addition (0, 3.5, and 10.5 gN m−2 year−1). The plant growth, biomass distribution, functional traits, and soil nutrient properties of the two trees were determined. Overall, N addition had positive effects on the aboveground and belowground biomass of P. tabuliformis, which also shifted its functional traits to an acquisitive strategy, while F. chinensis only increased root biomass distribution and fast traits as N increased. Furthermore, N supply increased the soil N and phosphorus availability of both trees and improved their root nutrient uptake capacity, resulting in an increase in their root–shoot ratio. Optimal partitioning theory could better explain why trees would invest more resources in roots, changing root structure and nutrient uptake, thus increasing root biomass allocation to adapt to a resource-poor environment. These findings highlight the importance of plant functional traits in driving the responses of biomass allocation to environmental changes for urban greening dominant tree species and could help to come up with new tree growth strategies in silvicultural practice for urban green space. [ABSTRACT FROM AUTHOR]

Urban forest is an integral part of the complex urban ecosystem, and tree canopy plays a key role in improving urban climatic environment. Urban Tree Canopy (UTC) is strongly linked to urban thermal environment and living quality of residents. In this study, Luoping County, a mountainous county in southwest China, was selected as the study area to uncover the inner connections between tree canopy and thermal environment, and provide relevant scientific references for the construction of livable forest cities in similar areas. Through eCongnition Developer, ENVI and ArcGIS software, the distribution of Land Surface Temperature (LST) and land cover types in the study area was extracted, 63 patches with super-large and extra-large tree canopy coverage selected, to explore the regulatory effect of UTC patches on urban thermal environment based on SPSS software. Results showed that the highest LST in the research area was 37.63 ℃, the lowest 24.73 ℃, and the average 30.83 ℃. Among the land cover types, the area of buildings and impervious surfaces was 1615.71 hm2, accounting for 55.76% of the total study area, which was the largest proportion and with widespread distribution; the area of grassland and water body was 57.48 hm2 and 12.35 hm2, respectively, taking up 1.98% and 0.43%, with a smaller proportion. Mean LST: impervious surface > bare land > grassland > tree canopy > water body. By increasing the area and perimeter of the patch covered by tree canopy, the cooling rate of the patch can be increased while the temperature inside the patch can be reduced. The relationship between the area and cooling rate is closer than that between perimeter and cooling rate. The increase of perimeter has a stronger alleviation effect on the internal temperature of the patch, whereas, the increase of area has a weaker effect in this respect. [ABSTRACT FROM AUTHOR]

Background: Continuous increasing carbon dioxide (CO2) has aggravated global warming and promoted urban tree planting projects for many countries. So it's imperative to select high carbon sequestering landscape tree species while considering their aesthetic values of urban green space. Results: 32 tree species were selected as test objects which were commonly used in landscaping in Zhengzhou, a typical northern city of China. To assess the comprehensive carbon sequestration potential of landscape tree species in different plant configuration types, we simultaneously considered their daily net carbon sequestration per unit leaf area (wCO2), daily net carbon sequestration per unit land area (WCO2) and daily net carbon sequestration of the whole plant (QCO2) through cluster analysis. Besides that, we found out the key factors affecting carbon sequestration potential of landscape tree species by redundancy analysis. Conclusion: Populus, P Stenoptera, P. acerifolia among large arbors (LA), V odoratissimum, P. Serratifolia, S. oblata among small arbors (SA), and B sinica var. Parvifolia, B. Megistophylla, L quihoui among shrubs (S) were recommended for local urban green space management. Photosynthetic rate (Pn), crown area (CA) and leaf area index (LAI) were the key factors which affected the comprehensive carbon sequestration potential both for LA, SA and S. [ABSTRACT FROM AUTHOR]

Because motor vehicles emit a large amount of PM2.5 pollution, traffic-related emissions have always been an important part of PM2.5 pollution. To better understand the influence of street trees on traffic-related PM2.5 pollution, our study focused on camphor trees, common evergreen urban street trees in central and southern China. We used ENVI-met for the simulation of PM2.5 pollution and to build a model to show the distribution of PM2.5 pollution along a section of Xinyao North Road in downtown Changsha City in central China. Based on this model, we constructed four other models with different heights, quantities, and distances between street trees, where each model had high feasibility and aimed to determine how these affect the PM2.5 concentration on the designated block. We performed simulations within different time frames in the year. We found that the wind can promote the diffusion of PM2.5 in the street canyon. Too dense a distribution of tall street trees will have a negative impact on PM2.5 concentration in street canyons. A moderate distance between street trees is conducive to the dispersion of pollutants. Because the crown of 5 m high street trees is small, its negative impact on the dispersion of wind and PM2.5 is relatively small, so further increasing the number of 5 m high street trees in street canyons with densely distributed tall street trees will have only a little more negative impact on PM2.5 concentration in street canyons. The PM2.5 concentration in the street canyon is generally better when the street trees are 5 m long, even if the number of 5 m high street trees is relatively large. Although the crown size of 15 m high street trees is larger than that of 10 m street trees, the vertical distance between the canopy of 15 m high street trees and the ground is usually greater than that of 10 m high street trees. The distance between the canopy of 15 m high street trees and the breathing zone is usually greater than that of the 10 m street trees. Longer distances lead to a weakening of its impact on PM2.5. When the 15 m high and 10 m high street trees are more scattered in the street, their effects on the PM2.5 concentration at the height of the breathing zone (1.5 m) are generally similar. [ABSTRACT FROM AUTHOR]

The family of Cryphonectriaceae (Diaporthales) contains many important tree pathogens and the hosts are wide-ranging. Tree species of Terminalia were widely planted as ornamental trees alongside city roads and villages in southern China. Recently, stem canker and cracked bark were observed on 2-6 year old Terminalia neotaliala and T. mantaly in several nurseries in Zhanjiang City, Guangdong Province, China. Typical conidiomata of Cryphonectriaceae fungi were observed on the surface of the diseased tissue. In this study, we used DNA sequence data (ITS, BT2/BT1, TEF-1a, rpb2) and morphological characteristics to identify the strains from Terminalia trees. Our results showed that isolates obtained in this study represent two species of Aurifilum, one previously described species, A. terminali, and an unknown species, which we described as A. cerciana sp. nov. Pathogenicity tests demonstrated that both A. terminali and A. cerciana were able to infect T. neotaliala and two tested Eucalyptus clones, suggesting the potential for Aurifilum fungi to become new pathogens of Eucalyptus. [ABSTRACT FROM AUTHOR]

As a famous street tree, camphor (Cinnamomum camphora) is widely planted worldwide. However, in recent years, camphor with root rot was observed in Anhui Province, China. Based on morphological characterization, thirty virulent isolates were identified as Phytopythium species. Phylogenetic analysis of combined ITS, LSU rDNA, β-tubulin, coxI, and coxII sequences assigned the isolates to Phytopythium vexans. Koch's postulates were fulfilled in the greenhouse, and the pathogenicity of P. vexans was determined by root inoculation tests on 2-year-old camphor seedlings; the symptoms of indoor inoculation were consistent with those in the field. P. vexans can grow at 15–30 °C, with an optimal growth temperature of 25–30 °C. The results of fungicide sensitivity experiments indicated that P. vexans was the most sensitive to metalaxyl hymexazol, which may be a useful idea for the future prevention and control management of P.vexans. This study provided the first step for further research on P. vexans as a pathogen of camphor, and provided a theoretical basis for future control strategies. [ABSTRACT FROM AUTHOR]

To assess the potential role of China's forest sector in achieving its goals of carbon (C) emission reduction and neutralization, it is essential to project C sequestered by forest ecosystems (FESs) and stored in harvested wood products (HWPs). It is also crucial to put these actions into a coherent framework of C accounting. Building on these steps, we show that during 2006–2020, the sector's biomass and soil C sequestration reached 2.589 petagrams (Pg) and 1.275 Pg respectively, and its C storage in HWPs added 0.491 Pg. These outcomes could have offset 11.76% of the country's cumulative C emissions. As China's emissions pass their peak in this decade, the proportion of carbon offset by FESs and HWPs will likely decrease below 10.00%. During 2006–2060, however, FES biomass and soil C sequestration would be 7.574 and 3.730 Pg, and C storage in HWPs would be 1.709 Pg, even under conservative assumptions. These estimates could lead to an overall offset ratio of 14.72%. In addition to highlighting the relevance of pursuing more aggressive nature-based solutions, this study can serve as an example of C accounting and tracking toward meeting countries' targets as specified in their Nationally Determined Contributions under the Paris Agreement. China's forest ecosystems and in-service wood products play an important role in removing and offsetting carbon (C) emissions. The forest sector actions are also cost-effective, especially if forest growth can be improved by adopting broad management practices. During the 2050s, these actions could more than offset the country's total emissions, allowing it to achieve C neutrality earlier than originally planned. To enhance the efficiency and productivity of forestry, China needs to further restructure its institutional arrangements and public policies. To fully account for forest sector's potentials, China must capture all possible C pools of the ecosystems, including in soil, urban trees/forests, and other trees outside of forests. [ABSTRACT FROM AUTHOR]

Surface ozone (O 3) poses a significant threat to urban vegetation health, and assessing the O 3 risk across woody species is of vital importance for maintaining the health of urban infrastructure. In the present study, Jarvis-type stomatal conductance model was parameterized for ten urban species in northern China. Incorporating the effects of time of day and diurnal O 3 concentration significantly enhanced the model performance. For different plant functional types (greening trees, greening shrubs, and orchard-grown trees), three parameterizations were established to estimate stomatal O 3 uptake (POD 1 , phytotoxic O 3 dose over an hourly threshold of 1 nmol m−2 s−1). The differences in POD 1 between greening trees and shrubs were primarily due to the difference in their stomatal sensitivity to light. Orchard-grown trees displayed the lowest O 3 removal capacity (lowest value of POD 1) because of their shorter growing season despite of high stomatal conductance. These results indicated that plant phenology and light responsiveness determined stomatal O 3 uptake, and the three parameterizations developed here could be applicable to various urban species in northern regions. Among climatic factors for O 3 risk assessment, O 3 concentration was the most important factor determining annual variation of POD 1 , which was primarily driven by air temperature. However, when O 3 pollution decreased, O 3 concentration exhibited less dependence on temperature and more dependence on light. These findings provide crucial insights for urban policy-makers and environmental scientists aiming to mitigate O 3 pollution effects and enhance urban vegetation health. • Stomatal multiplicative model was parameterized for 10 urban species in north China. • Plant phenology and light responsiveness determined stomatal O 3 uptake across species. • Orchard-grown trees displayed low stomatal O 3 uptake due to short growing season. • O 3 concentration was the most important climatic factor determining POD value. [ABSTRACT FROM AUTHOR]

Background: Semiothisa cinerearia belongs to Geometridae, which is one of the most species-rich families of lepidopteran insects. It is also one of the most economically significant pests of the Chinese scholar tree (Sophora japonica L.), which is an important urban greenbelt trees in China due to its high ornamental value. A genome assembly of S. cinerearia would facilitate study of the control and evolution of this species. Results: We present a reference genome for S. cinerearia; the size of the genome was ~ 580.89 Mb, and it contained 31 chromosomes. Approximately 43.52% of the sequences in the genome were repeat sequences, and 21,377 protein-coding genes were predicted. Some important gene families involved in the detoxification of pesticides (P450) have expanded in S. cinerearia. Cytochrome P450 gene family members play key roles in mediating relationships between plants and insects, and they are important in plant secondary metabolite detoxification and host-plant selection. Using comparative analysis methods, we find positively selected gene, Sox15 and TipE, which may play important roles during the larval-pupal metamorphosis development of S. cinerearia. Conclusion: This assembly provides a new genomic resource that will aid future comparative genomic studies of Geometridae species and facilitate future evolutionary studies on the S. cinerearia. [ABSTRACT FROM AUTHOR]

The dew condensation frequency is high, and the dew amount is heavy in urban ecosystems. During the condensation process, particulate matter acts as a condensation core, playing an important role in purifying the air. At night, dew mainly condenses on plant leaf surfaces, the plant leaves settle the particles in the dew, and some of the particles are resuspended into the atmosphere in the process of dew evaporation after sunrise. This paper monitored the condensation and evaporation processes of dew on four common plants in Changchun city from June to September 2020. By analyzing the mass and size of particles on different leaves after dew condensation and evaporation, the ability of different plants to retain particles in dew was analyzed. The results showed that there was no significant difference in the TSP capture ability during dew condensation between Buxus sinica (Rehd. et Wils.) Cheng subsp. sinica var. parvifolia M. Cheng, Syringa oblata Lindl., Hemiptelea davidii (Hance) Planch., and Pinus tabuliformis Carrière, with a TSP content of 0.21 ± 0.06 μg/cm2. Coarse particulate matter is the main type of deposit in the dew condensation stage. Particulate deposition varied according to species, leaf shape, and microstructure. The proportion of TSP remaining on leaves after dew evaporation from Pinus tabuliformis Carrière, Hemiptelea davidii (Hance) Planch., Buxus sinica (Rehd. et Wils.) Cheng subsp. sinica var. parvifolia M. Cheng, and Syringa oblata Lindl. tree was 89.7 ± 3.9%, 80.6 ± 3.6%, 75.9 ± 4.5%, and 71.4 ± 3.7%, respectively. The ability of the leaves to trap fine particles was significantly higher than that for coarse particles (P < 0.05) after dew evaporation. The highest amount of particle captured by Syringa oblata Lindl. individual was 15.17 g/y during dew condensation, and the amount of remaining particles after dew evaporation was 10.83 g/y. This paper provides a theoretical basis for the selection of tree species for urban greening. [ABSTRACT FROM AUTHOR]

A large number of trees have been planted in built-up areas to improve the urban environment, but the effects of tree cover on spontaneous understory herbs are not yet well understood. This study surveyed spontaneous herbs in two kinds of habitats (habitats with and without tree cover) in the built-up area of the small city Junlian in Sichuan Province, China. A total of 222 species of spontaneous herbaceous plants in 180 genera of 71 families were recorded, including a vulnerable species and six species endemic to China. Although the overall species richness values were similar in the two kinds of habitat, the average species richness per quadrat of all plants, perennials, plants with the dwarf growth form, and animal-dispersed plants was significantly higher in the habitats with tree cover than in those without tree cover. The overall species association was significantly positive in the habitats with tree cover (VR = 1.51, p < 0.05) and neural (VR = 0.86) in the habitats without tree cover. Among the top 25 frequently recorded species in each kind of habitat, the species association of plants with the same trait combination type differed greatly in the two kinds of habitats. For the species association between annuals, only 13.33% of species pairs were significantly associated in the habitats with tree cover, while 22.22% of the species pairs were significantly negatively associated in the habitats without tree cover. For the species association between plants with tall growth forms, the proportion of significant positive associations in the habitats with tree cover was approximately twice than in the habitats without tree cover. For the species association between plants with the dwarf growth form, the proportion of negative associations in the habitats without tree cover was approximately twice that in the habitats with tree cover. Species with the same dispersal mode generally had a very low proportion of negative interspecific associations or a high proportion of positive interspecific associations in habitats unfavorable to their establishment. Our findings suggest that tree cover can improve the species richness of the spontaneous herbaceous species beneath them and profoundly influence interspecific coexistence relationships in a built-up area. [ABSTRACT FROM AUTHOR]

Extracting street trees from mobile Light Detection and Ranging (LiDAR) point clouds is still encountering challenges, such as low extraction accuracy and poor robustness in complex urban environment, and difficulty in the segmentation of overlapping trees. To solve these problems, this paper proposed a street tree extraction and segmentation method based on spatial geometric features of object primitives. In this paper, mobile LiDAR point clouds were first segmented into object primitives based on the proposed graph segmentation method, which can release the computation burden effectively. According to the spatial geometric features of the segmented object primitives, stem points were extracted. In doing so, the robustness and accuracy for stem detecting can be improved. Furthermore, voxel connectivity analysis and individual tree optimization were combined successively. In doing so, the neighboring trees could be separated successfully. Four datasets located in Henan Polytechnic University, China, were used for validating the performance of the proposed method. The four mobile LiDAR point clouds contained 106, 45, 76, and 46 trees, respectively. The experimental results showed that the proposed method can achieve the performance of individual tree separation in all the four testing plots. Compared to the other three methods, the proposed method can make a good balance between the commission and omission errors and achieved the highest average F1 scores. [ABSTRACT FROM AUTHOR]

Background: Paved urban environments can pose great threats to the physiological functioning and ecological services of street trees. In this context, assessment of leaf phenotypic plasticity is crucial for understanding the ecological strategy of tree species under impervious pavements. Results: In this study, we measured a set of leaf economic traits, hydraulic traits of Cinnamomum camphora, and surrounding environmental factors in a street site (the soil was covered by the impervious pavement) and a park site (the soil was covered by grass) in Hefei, eastern China. Compared with the park site, trees in the street site had higher stomatal length (SL), leaf thickness (LT), maximum photochemical quantum yield of photosystem II (Y(II)), and lower stomatal density (SD), specific leaf area (SLA), the leaf water potential at 50% loss of hydraulic conductance (P50), and leaf turgor loss point (TLP). Redundancy analysis showed that air relative humidity and volumetric soil water content caused these traits to be altered. Conclusions: Our results showed that C. camphora adapted to the street pavement environment through the coordination of leaf economic and leaf hydraulic traits, and adopted the slow investment return type in the leaf economic spectrum and high drought resistance to meet its actual physiological needs. This finding provides a new perspective for understanding the physiological strategies of street trees to adapt to urban pavement environments. [ABSTRACT FROM AUTHOR]

• NO X inhibits the growth of forests, causing vegetation browning of urban green space. • Urbanization and climate change are positive with NO X , co-limiting forest production. • The responses of forest understory layers to environmental changes are different. • Urbanization increases leaf herbivory and lead to severe pests of urban green space. Nowadays, atmospheric concentrations of nitrogen oxides (NO X) have increased rapidly and exceeded the threshold of ecosystems, inevitably affecting the plant growth and community stability, especially in urban green space. The increase of atmospheric NO X is also accompanied by natural and anthropogenic environmental change, which also bring severe environmental stresses on green vegetation. To better understand drivers that contribute to the vegetation changes, this study explored the interaction among atmospheric NO X , climate, terrain, and urbanization, and its impact on the tree leaf and forest community traits, using a dataset with 118 plots of tree communities composed of 5781 trees across distinct types of urban green space in Tianjin, a highly urbanized metropolis in China. The results indicated that atmospheric NO X concentration showed a positive association with urbanization and temperature, which co-limited the tree growth and resulted in the vegetation browning of urban green space. The responses of coniferous and broadleaved forests were different, whose understory herbaceous diversity and height had contrary tendencies to environmental change. Meanwhile, urbanization intensified atmospheric N deposition and heat island effect, increasing the leaf chlorophyll contents of tree species in urban green spaces. While leaf herbivory showed positive correlation with urbanization, temperature, and evaporation only in the high NO X regime. Overall, this study found that atmospheric NO X could be used as a good indicator of urbanization. These findings also advanced our recognition of the environmental driving factors of green vegetation dynamics, and provided references for the research of elsewhere. [ABSTRACT FROM AUTHOR]

Tilia tomentosa Moench (silver linden) is a globally preferred option for landscaping and street tree planting. Its intentional introduction to China in recent years has led to widespread cultivation. In 2021, a leaf spot disease significantly impacted silver linden trees in a sentinel garden in China, with an average incidence and disease severity of 94.3% and 5.0, respectively, adversely affecting the trees' growth and development. In this investigation, potential fungal pathogens were isolated from the affected leaves, and Koch's postulate was subsequently employed to validate the pathogenicity of the fungal isolates (TM-1 and TM-2). The pathogen was unequivocally identified as Colletotrichum cliviicola through a combination of morphological observation and a multi-locus analysis (ITS, ACT , ApMat , CAL , CHS-1 , GAPDH , and TUB2). This marks the first record of C. cliviicola affecting silver linden in China. The information provided a valuable foundation for the rapid detection and effective prevention and control of the diseases affecting linden trees. • The introduced silver linden in China was affected by leaf spot disease. • Pathogen was identified as Colletotrichum cliviicola. • First report of C. cliviicola causes silver linden leaf spot in China. • Sentinel garden provide early warning information on pathogens to exporting countries. [ABSTRACT FROM AUTHOR]

Urban trees perform various ecosystem services, and tree DBH (trunk diameter at breast height, 1.3 m above the ground) can act as a surrogate measure of these important functions. However, DBH has seldom been studied in relation to spatial variation, possible underlying drivers, and response to urbanization. Our field investigation collected data from tree species within Urban Function Units (UFUs) in south China's coastal city Zhanjiang, which has recently experienced rapid urbanization. The land cover of UFUs was determined by visual interpretation of satellite images. Trees with DBH > 2 cm were assessed, and vines were excluded. We recorded 12,434 trees in the green space belonging to 185 species, 137 genera, and 51 families. The dominant DBH range, 5‒15 cm, accounted for 43.72% of the total stems. The DBH of 33 individuals exceeded 90 cm, 20 of which were Ficus species. At 32.39 cm, the average DBH in commercial areas was the highest among the UFU types, while woodlands had the lowest at 7.11 cm. GLMM analysis showed that UFU types, landscape configuration, land cover, and construction age were all significantly associated with tree DBH. Tree DBH had a significant positive correlation with impervious surface area and a negative correlation with green space surface area. The largest trees were mainly distributed in urban villages, schools, parks, and transportation areas. Understanding urban tree DBH structure and its related factors can promote sustainable urban-forest development and management. [ABSTRACT FROM AUTHOR]

Street trees are important components of an urban green space and understanding and measuring their ecological and cultural services is crucial for assessing the quality of streets and managing urban environments. Currently, most studies mainly focus on evaluating the ecological services of street trees by measuring the amount of greenness, but how to evaluate their aesthetic functions through quantitative measurements of street trees remain unclear. To address this problem, we propose a method to assess the aesthetic functions of street trees by quantifying the shape of greenness inspired by assessments of skyline aesthetics. Using a state-of-the-art mobile mapping system, we collected downtown-wide lidar data and panoramic images in Jinzhou City, Hebei Province, China. We developed a method for extracting the canopy line from the mobile lidar data, and then identified two basic elements, peaks and gaps, from street canopy lines and extracted six indexes (i.e., richness of peaks, evenness of peaks, frequency of peaks, total length of gaps, evenness of gaps and frequency of gaps) to describe the fluctuations and continuities of street canopy lines. We analyzed the abundance and spatial distribution of these indexes together with survey responses on the streets' aesthetics and found that most of them were significantly correlated with human perception of streets. Compared to indexes of amount of greenness (e.g., green volume and green view index), these shape indexes have stronger influences on the physical aesthetic beauty of street trees. These findings suggest that a comprehensive assessment of the aesthetic function of street trees should consider both shape and amount of greenness. This study provides a new perspective for the assessment of urban green spaces and can assist future urban greening planning and urban landscape management. [ABSTRACT FROM AUTHOR]

The aboveground biomass (AGB) of trees plays an important role in the urban ecological environment. Unlike forest biomass estimation, the estimation of AGB of urban trees is greatly influenced by human activities and has strong spatial heterogeneity. In this study, taking Hengqin, China, as an example, we extract the tree area accurately and design a collaborative scheme of optical and lidar data. Finally, five evaluation models are used, including two deep learning models (deep belief network and stacked sparse autoencoder), two machine learning models (random forest and support vector regression), and a geographically weighted regression model. The experimental results show that the deep learning model is effective. The result of the stacked sparse autoencoder, which is the best model, is that R² = 0.768 and root mean square error = 18.17 mg/ha. The results show that our method can be applied to estimate the AGB of urban trees, which greatly influences urban ecological construction. [ABSTRACT FROM AUTHOR]

Urban trees and forests provide multiple ecosystem services for urban dwellers. However, forest water use for these benefits has become one of the critical concerns in dryland regions where water is limited. Negative forest water use impacts could be reduced by selecting tree species with low rates of transpiration. However, the possible changes of urban tree transpiration and its biophysical controls are still unclear. This study monitored the sap flow of a 58‐year‐old Chinese pine (Pinus tabulaeformis) plantation in a semiarid urban environment of northern China. Soil moisture played an important role in stand transpiration (Ec). Ec had a strong positive relationship with vapour pressure deficit (VPD) and solar radiation (Rs) when soil water was sufficient. In addition, the sensitivity of leaf stomata to VPD was not related to leaf and branch water potential. Under soil water stress, Ec was significantly reduced by 63.1% (p < 0.001) and was weakly related to VPD and Rs. Canopy conductance (gc) was reduced (p < 0.001) by 74.3% due to leaf stomatal closure, and the sensitivity of leaf stomata to VPD was significantly increased (p < 0.05) with increasing leaf and branch water potential. Wind speed had no significant effects on Ec. P. tabulaeformis tended to be isohydric with a relatively constant midday leaf water potential (i.e. −2.46 to −2.92 MPa) and strong stomatal regulation as a function of soil water stress. However, slopes (0.53–0.56) of the linear relationship between m (dgc/dlnVPD) and reference canopy conductance were significantly lower than the widely recognized 0.6 (p < 0.001). Therefore, urban tree transpiration drivers and forest impacts need to be clarified to better understand the proper tradeoff between water consumption and ecological services for urban areas. [ABSTRACT FROM AUTHOR]

Urban expansion leads to changes in the visual aesthetic quality and ecological degradation of the surrounding slope forest landscapes. Color is a crucial visual element to examine when viewing this large-scale slope forest landscape from a long distance. This is particularly true for the autumn color of slope forest, which is very attractive to the public. An exploration of the relationship between the change in color of a natural slope forest and its visual aesthetic quality enables the implementation of the configuration of superior aesthetic tree species. Therefore, it can provide aesthetic rules and a reference to configure local tree species to support their visual aesthetic quality, ecological sustainability and native biodiversity restoration in a local urban slope forest. However, such research is critically lacking. This study investigated the visual aesthetic quality of the color dynamics of a natural slope forest in Jiaozi Mountain, China in the autumn. We analyzed both the composition of tree species and the changes in color for each species of tree in nine forest sites that exhibited superior visual aesthetic quality. The results showed that the forests with superior visual aesthetic quality were more green, red, and yellow, had moderately higher saturation and value, more obvious color contrast, and diverse colors with primary and secondary contrast. Diverse and balanced color patches or a dominant color patch contrasted by many small patches with interspersed color components also highlighted the superior visual aesthetic quality of slope forest features. Different combinations of color features can result in high visual aesthetic quality. The 84 tree species in the superior visual aesthetic quality forests primarily displayed 10 types of color changes that varied as green, yellow, blue, red, withered yellow, withered red and gray. [ABSTRACT FROM AUTHOR]

Street greening, an indispensable element of urban green spaces, has played an important role in beautifying the environment, alleviating the urban heat island effect, and improving residents' comfort. Vegetation coverage is a common index used for measuring street greening. However, there are some shortcomings in the traditional evaluation methods of vegetation coverage. Part of the vegetation coverage cannot be determined from a two-dimensional perspective, such as shrubs and green walls. In this paper, the Sentinel-2 image was used to extract the street fractional vegetation cover (SFVC) and the Baidu street view panoramas were used to extract the green view index (GVI). To overcome the lack of a single perspective from the street vegetation coverage evaluation, the above two indices were merged to construct a comprehensive street greening evaluation index (CSGEI). The research area is the Longhua District of Shenzhen city in Southern China. All three indices were divided into five classes using natural breakpoint methods based on previous research experience. The results showed that Baidu street view panoramas could effectively identify shrubs and green walls that were deficient in the Sentinel-2 image. The GVI is a supplement to the street vegetation coverage. The SFVC and GVI were divided into five classes, from L1 to L5 implying a gradual increase in the percentage of the vegetated area. The result has shown that the SFVC was in the L1, accounting for 53.68%. After index merging, the process of accounting for the L1 decreased to 31.29%. The multiperspective integrated CSGEI could comprehensively measure the distribution information of street greening and guide the planning and management of urban green landscapes. [ABSTRACT FROM AUTHOR]

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University campuses usually have more trees and can provide various ecosystem services. However, there are few reports on tree ecosystem services of Chinese university campuses, especially in northern China. This study investigated the trees in the campus of Shenyang Institute of Technology and analyzed its ecological benefits and monetary value through i-Tree Streets. The campus trees contained a total of 5193 trees of 66 species, of which Catalpa ovata G. Don, Acer mono Maxim., Rhus typhina Nutt, and Salix babylonica L. accounted for 59.7% of the total number. The age structure of the trees in the campus was not ideal, with 71.5% of young trees, 24.0% of maturing trees, 4.5% of mature trees, and only 0.04% of old trees. The trees in the campus provided more energy saving benefits ($60,850, $11.7/tree), carbon reduction benefits ($34,318, $6.6/tree) and aesthetic benefits ($30,150, $5.8/tree). The benefits resulted from air pollutant removal ($12,889, $2.5/tree) and rainwater runoff interception ($15,534, $3.0/tree) were smaller. In addition, tree species with more maturing trees and mature trees (i.e., with larger diameter at breast height) and large leaf area in the campus contributed significantly to ecosystem services. Our results can provide suggestions and certain insights for Chinese campus greening managers in tree species selection and tree management. [ABSTRACT FROM AUTHOR]

• In around 95 % of cities in China, TCE tends to be underestimated. • Urban heterogeneity plays a crucial role in the accurate evaluation of TCE. • RTCE can minimize the impacts of heterogeneous urban landscapes. • Heat mitigation potential of trees in high-rise urban environments is undervalued. As cities worldwide grapple with the escalating challenges of extreme heat events, afforestation can serve as an effective adaptation measure to mitigate heat stress. This study presents a comprehensive nationwide assessment of urban tree-induced cooling effects and provides a more accurate and robust methodology that accounts for the influence of spatial heterogeneity within the complex urban environment. Results reveal that the conventional method for assessing cooling efficiency (TCE) is substantially influenced by urban heterogeneity, in terms of both horizontal and vertical structures. The revised tree cooling efficiency (RTCE), designed to minimize the impacts of other land cover types on surface temperature variations, was proved to be a more accurate estimation. In 362 out of 379 cities across China, TCE tended to underestimate the cooling effects as a result of spatial heterogeneity. The nationwide average disparity between RTCE and TCE was approximately 0.047±0.0145 ℃ per percent (95 % confidence interval). The largest differences were observed among high-rise environments, highlighting the undervalued heat mitigation potential of urban trees in compact and densely populated urban settings. This study emphasizes the considerable potential of urban tree-cooling effects in mitigating heat stress in the face of a warming planet. [Display omitted] [ABSTRACT FROM AUTHOR]

• Simulated effects of vegetation on microclimate of different urban blocks in winter. • Simulated effects of vegetation on building heating energy in different urban blocks. • Vegetation brought a building heating load increase of 7.16 % in a sunny day at most. • Vegetation brought a building heating load decrease of 2.80 % in a cloudy day at most. • Offered evergreen urban vegetation strategies for high-density cities in cold region. As an important landscape, the evergreen vegetation is prevailing, even in cold region cities. However, the impacts of promoting vegetation on microclimate and building heating load (BHL) are still inexplicit. This study validated the feasibility of a new-developed coupled model that linked ENVI-met and EnergyPlus, for predicting the microclimate and BHL in winter. The impacts of vegetation configuration changes on the performances of three typical urban blocks in Xi'an, a high-density city in the cold region of China, were then evaluated. When the leaf area index of green lands increased from 0.79 to 4.77 m2/m2, a decrease of 3.27 °C on mean radiant temperature, a decrease of 0.48 m/s on wind speed, and an increase of 0.47 °C on air temperature at the block scale could be observed. To the three blocks, the BHL of thermal zones in the height range of tree canopy increased by 7.16 %, 1.52 % and 3.57 % during a sunny day, and decreased by 2.80 %, 0.55 %, and 0.06 % during a cloudy day maximally. Overall, the evergreen vegetation produced negative impacts on the building energy efficiency of cold region cities. For urban planners, it's advisable to concentrate evergreen plants in high-rise blocks to mitigate such disadvantages. [ABSTRACT FROM AUTHOR]

Plant leaf respiration is one of the critical components of the carbon cycle in terrestrial ecosystems. To predict changes of carbon emissions from leaves to the atmosphere under a warming climate, it is, therefore, important to understand the thermodynamics of the temperature response of leaf respiration. In this study, we measured the short-term temperature response of leaf respiration from five different urban tree species in a subtropical region of southern China. We applied two models, including an empirical model (the Kavanau model) and a mechanistic model (Macromolecular Rate Theory, MMRT), to investigate the thermodynamic properties in different plant species. Both models are equivalent in fitting measurements of the temperature response of leaf respiration with no significant difference (p = 0.67) in model efficiency, while MMRT provides an easy way to determine the thermodynamic properties, i.e., enthalpy, entropy, and Gibbs free energy of activation, for plant respiration. We found a conserved temperature response in the five studied plant species, showing no difference in thermodynamic properties and the relative temperature sensitivity for different species at low temperatures (<42°C). However, divergent temperature response among species happened at high temperatures over 42°C, showing more than two-fold differences in relative respiration rate compared to that below 42°C, although the causes of the divergent temperature response remain unclear. Notably, the convergent temperature response at low temperatures could provide useful information for land surface models to improve predictions of climate change effects on plant respiration. [ABSTRACT FROM AUTHOR]

Species-specific sex pheromones play key roles in moth sexual communication. Although the general pathway of Type-I sex pheromone biosynthesis is well established, only a handful of genes encoding enzymes involved in this pathway have been characterized. Streltzoviella insularis is a destructive wood-boring pest of many street trees in China, and the female sex pheromone of this species comprises a blend of (Z)-3-tetradecenyl acetate, (E)-3-tetradecenyl acetate, and (Z)-5-dodecenyl acetate. This organism therefore provides an excellent model for research on the diversity of genes and molecular mechanisms involved in pheromone production. Herein, we assembled the pheromone gland transcriptome of S. insularis by next-generation sequencing and identified 74 genes encoding candidate key enzymes involved in the fatty acid biosynthesis, β-oxidation, and functional group modification. In addition, tissue expression patterns further showed that an acetyl-CoA carboxylase and two desaturases were highly expressed in the pheromone glands compared with the other tissues, indicating possible roles in S. insularis sex pheromone biosynthesis. Finally, we proposed putative S. insularis biosynthetic pathways for sex pheromone components and highlighted candidate genes. Our findings lay a solid foundation for understanding the molecular mechanisms underpinning S. insularis sex pheromone biosynthesis, and provide potential targets for disrupting chemical communication that could assist the development of novel pest control methods. [ABSTRACT FROM AUTHOR]

• Increased temperature improved plant growth and photosynthetic carbon fixation. • O 3 inhibited growth, and Quercus mongolica has a self-repair ability to O 3 stress. • The adverse effects of O 3 on growth and C fixation were mitigated by air warming. • Urban trees show a species-specific difference in plant functional traits. With continuous urbanization and climate warming, increased air temperature and elevated ozone (O 3) concentration often co-occur in many urban areas, but we still lack information about the interactive effects of warming and elevated O 3 on urban trees. In the present experiment, the single and combined effects of increased air temperature (IT, ambient air temperature + 2 °C) and elevated O 3 (EO, ambient air O 3 concentrations + 80 ppb) on carbon (C) fixation and allocation in Quercus mongolica and Pinus tabuliformis, which are widely used as street tree species in urban areas of China, were investigated over two consecutive growing seasons by using 13C isotope techniques. The results showed that IT increased biomass, photosynthetic gas exchange parameters and total 13C content of both tree species. Compared to ambient temperature, IT significantly increased the total 13C content labelled by 56.6 % in Q. mongolica and by 31.2 % in P. tabuliformis in 2021. Elevated O 3 induced a decrease in biomass and net photosynthetic rate (P n) in both tree species. Compared to ambient O 3, elevated O 3 significantly decreased P n by 52.6 % in Q. mongolica and by 37.4 % in P. tabuliformis in 2020. The treatment EO decreased 13C allocation to roots but increased 13C content and distribution in leaves in Q. mongolica. These findings demonstrated that EO inhibited the growth and photosynthesis of the two tree species. Our results showed that Q. mongolica was more sensitive to IT and EO than P. tabuliformis , but the former has a self-repair mechanism under increased O 3 stress as it is able to invest more carbon to repair leaf damage to a certain extent. Our study also found that the total biomass, relative growth rate, P n and total 13C content remained higher under the combination of IT and EO compared to EO alone, suggesting that moderate warming may mitigate the negative effects of elevated O 3 stress to some extent. [ABSTRACT FROM AUTHOR]

• A rapid and robust street canyon radiation model with trees is developed. • The effect of trees on radiative transfer in street canyons is considered. • A novel urban solar potential mapping framework is proposed. Street-level solar radiation estimation can help to better understand the influence of solar radiation on urban microclimate, outdoor thermal comfort and health, solar energy utilization, and building energy savings. However, existing urban canyon radiation models based on Monte Carlo ray tracing are challenging to apply in real practice due to limited applicability and high computational efforts. A flexible and robust mathematical model for solar radiation in urban canyons is proposed in this study to estimate solar radiation potential at the street level quickly and can be applied to the urban scale. The newly developed model considers the effect of trees on street canyon radiative transfer based on some assumptions and simplifications. Using the matrix method to resolve the infinite number of multi-reflections, the model accurately predicts solar radiation inside the street canyon compared to experimental data. The maximum root mean square error (RMSE) in the model prediction is 52.7 W/m2 and 14.5 W/m2, respectively, for urban canyons without and with trees in the studied case. And the Pearson correlation coefficient (r) is above 0.987 for all scenarios. An open-source Python script module for the model application is provided and can be integrated with other models or software platforms. The model has been used to estimate solar potential on the street and urban scales taking Chongqing city, China as an example. It is proven that the model is helpful for rapid assessment of solar radiation at the street and urban scales, serving urban design and planning. [ABSTRACT FROM AUTHOR]

The response of urban trees to the environment is the key content to explain the functional toughness of urban green space. However, how urban greening trees adapt to the dry and hot environment of the city remains unclear due to the single index and the limitations of the research area. We selected four representative cities in northern China with different regional dryness and measured 18 economic, hydraulic and anatomical traits of the common greening tree species (Fraxinus chinensi s Roxb). The results show that there was generally a significant divergence in plant functional traits across urban dryness, and the traits have strong plasticity. As urban dryness increases, the number of leaf veins closed loops increases, forming a more complete network system of veins. While a significant decrease in the vessel vulnerability index further indicates the increased drought tolerance of urban trees to resist dry and hot environments. The increase of dryness leads to the decrease of vessel hydraulic diameter and area. The reduction in the vessel vulnerability index indicates an increase in the drought resistance of the twigs, which may be related to the input and distribution of resources in the branches and leaves. There was a strong correlation between plant economic-anatomical-hydrological traits. Under the stress of a dry urban environment, plants prefer to invest resources in the water sparing capacity of the stem, as well as in the construction of defence structures and nutrient storage capacity of the leaves. [Display omitted] • Environmental variable (urban dryness) was significantly correlated with economic, hydraulic and anatomical traits. • There was more positive correlation (cooperative development) between vessel traits and vein traits, while there was more negative correlation (trade-off) between stomatal traits and vein traits. • Urban dryness promotes the formation of a more complete vein network system. • Under the stress of urban arid environment, urban trees adopt the strategy of sacrificing the supporting function of trunk to ensure the safe transportation of water. [ABSTRACT FROM AUTHOR]

There are many factors that affect how urban tree species absorb and use nutrients, but little is known about the impact of pavement in urban areas. In this study, we selected four common urban tree species— Platanus x acerifolia , Metasequoia glyptostroboides , Robinia pseudoacacia , and Pinus thunbergii —and three pavement coverage categories—unpaved, semi-paved, and fully paved—in Qingdao, a typical city in northern China, to investigate changes in the leaf nutrient utilization strategies of tree species in paved environments. The nitrogen (N) resorption efficiency (NRE) and phosphorus (P) resorption efficiency (PRE) of R. pseudoacacia and the NRE of M. glyptostroboides increased in semi- and fully paved environments. Additionally, the N resorption proficiency of M. glyptostroboides increased significantly with pavement coverage, indicating that the biochemical limitation on N resorption was weakened. Similarly, the contents of N, P, and potassium (K) in R. pseudoacacia and N and K in M. glyptostroboides significantly increased with pavement coverage. This indicates that R. pseudoacacia , a nitrogen-fixing Fabaceae tree species, and M. glyptostroboides , a deciduous Cupressaceae tree species, can better adapt to pavement in urban settings, and even high pavement coverage levels can induce higher nutrient contents and resorption capacities. In addition, M. glyptostroboides showed potentially poor adaptability for N, P, and K uptake in the more stressful pavement environments, and P. x acerifolia showed relatively poor adaptability in P-limited environments. Robinia pseudoacacia associates with nodule-forming nitrogen-fixing bacteria, thus retaining more N in its leaves and showing a low NRE. These findings not only provide additional insight into tree growth at varying pavement coverages but also preliminary guidance for tree species selection to promote resilience in urban areas. • Ground pavement over tree root systems affected nutrient resorption capacity of urban trees. • Urban tree species exhibited different adaptability strategies under different pavement environments. • Differences in ecological plant type may explain nutrition differences. [ABSTRACT FROM AUTHOR]

The large-scale urbanization has changed the surface characteristics of cities, seriously affected the urban heat balance, and worsened the urban thermal environment. The regulation of vegetation coverage on urban climate has received extensive attention. This study aims to assess and predict changes in the urban thermal environment of Hangzhou by monitoring the variation of the urban thermal field variance index (UTFVI) affected by fractional vegetation cover (FVC) changes. The results indicate that the area of high level FVC will likely decrease by 52.91%, while the area of lower level FVC will likely increase by 33.83% from 1990 to 2030. Furthermore, the area of the strongest level UTFVI shows a significant trend of expansion, increasing by 467.299 km2 from 1990 to 2030, while the area of other levels UTFVI shows different degrees of decrease. Specifically, the area of strong and stronger levels UTFVI decreased by 149.641 km2 and 271.464 km2, respectively. The spatial correlation between the FVC and UTFVI changes is significant and negative, with p -values less than 0.01 and negative coefficients. The absolute value of the coefficient will decrease from 0.416 to 0.246 from 1990 to 2030, and the correlation between FVC and UTFVI changes shows a decreasing trend. The linear regression analysis demonstrates a significant negative correlation between the FVC and UTFVI, with coefficients ranging from −0.470 to −0.280 and p -values less than 0.001, further indicating that the FVC has a mitigating effect on the urban thermal environment. This study provides new insights into thermal environment governance and urban sustainable development. [ABSTRACT FROM AUTHOR]

Urban heat island (UHI) often cause negative impact and has been linked to heart stroke rate, morality, human comfort, energy consumption and air pollution. Fortunately, urban green spaces have been considered as an effective element to mitigate UHI through their cooling effect. However, further empirical research is necessary in order to efficiently guide the design and planning of urban green space. We observed the impacts of urban park's tree, grass and waterbody on microclimate inside the Olympic park of Beijing during summer days. The results indicated that, on average, the park was 0.48–1.12 °C cooler during the day, as well as increased air humidity 2.39–3.74% and reduced human comfort index 1.02–2.43 to generate more comfortable thermal environment. Urban park's cluster trees with short ground vegetation generated higher cooling effect than single trees, grass and waterbodies; proper irrigation regime enhanced the cooling effect of grasses, even the irrigated grass have similar cooling effect with small waterbody on sunny, windless summer days. Therefore, we advise to increase undergrowth coverage and grass irrigation management in order to take advantage of cooling effect of urban parks. [ABSTRACT FROM AUTHOR]

The phenomenon of global warming and urban heat island has raised the attention for the outdoor thermal comfort. Vegetation in the improvement of urban micro-climate has been confirmed by a large number of scholars. The problem of the uncomfortable summer climate in China's Cold region didn't get enough research. In this paper, the summer thermal comfort of the street canyon has been studied. The main research intent is to analyze the relationship between the street tree pattern and the thermal comfort of street canyon. It’s demonstrated that, in north-south street, it is suitable for the arrangement of street tree to be at the centre on one side of the street. The higher the height of the street tree, the more comfortable thermal environment the street gets. However, when the ratio of the street tree height to the street building is greater than 10:18, the improvement effect decreases. In east-west street, planting the street tree clinging to the street buildings can provide a better thermal comfort improvement effect. The result of this study can serve as a guide to the greening design in China B-cold region and other regions with similar climatic conditions. [ABSTRACT FROM AUTHOR]

Selecting tree species for urban greening requires a good understanding of the performance of the species under different types of disturbances. However, information on performances of many species is still not available today. In this study, we used an extensive data set gathered through a systematic literature review to analyze the impacts of five major types of disturbances on urban tree species in China. Our results showed that there were distinctive spatial patterns of occurrences of these disturbances on urban trees. Urban trees in north China were mainly disturbed by low temperature, snow, and wind. In central China, low and high temperatures were major disturbances. Urban trees in south China suffered greatly from low temperature and wind. Pests and disease were reported more frequently in east China, where most cities are located. Of the 1010 taxa of trees reported over the 120 cities in the study-which included 723 taxa identified to the species level, 264 identified to the sub-species level, and 23 identified to the genus level-the impacts of these disturbances varied widely. We recommend that cities reduce or avoid the use of tree species that perform poorly under these disturbances. [ABSTRACT FROM AUTHOR]

The species composition of urban green spaces (UGSs) in different climate areas has been found to be homogenized compared with that of rural forests (RFs). However, the homogenization degree in response to moisture as a single ecological factor is still unknown. Here, we used 18 cities in the temperate zone of China to analyse the tree species composition and diversity index of UGSs and compare them with those of RFs. The results showed that (1) a total of 462 tree species were recorded in the UGSs in 18 cities, and 88 species were found in the UGSs of more than 9 cities. Among the 88 species, 47 species occur in UGSs in humid, semiarid and arid areas, including Ginkgo biloba , Salix babylonica , Acer mono , and Pinus tabuliformis. (2) The tree species richness and Simpson index of UGSs tended to converge (CV UGS ≈ 1/2 CV RF) along the moisture gradient (mean annual precipitation 200–800 mm). (3) The similarity of tree species composition among UGSs (J ∼ 0.30) was significantly higher than that among RFs (J ∼ 0.07), revealing homogenization among cities in areas with different humidity conditions. (4) The similarity increased when the difference in moisture and per capita GDP (gross domestic production) of cities decreased, indicating that ecological and economic factors jointly affected the homogenization of UGSs. This study also provides guidance for the management of UGSs. • Tree species composition in UGSs became homogenized along a moisture gradient. • Tree species diversity in UGSs converged on a gradient from humid to arid areas. • Tree composition similarity increased when the moisture of cities became similar. • Economic development promoted tree diversity in the UGSs of cities. [ABSTRACT FROM AUTHOR]

Negative environmental impacts of golf courses have received more attention than positive ecological contributions. We studied the mature tree communities and their legacy effect in a historical urban-fringe golf-course site in Hong Kong covering 170-ha with well-managed natural-cum-cultural landscape. Some 44.3 % of the site is covered mainly by large trees forming a mature peri-urban forest. The 94 species in 35 families offer a high species diversity exceeding local secondary and climax fengshui woodlands with notable rare and protected species. Tree species composition, richness and legacy effects brought by anthropogenic and natural factors were investigated by three habitats with varying naturalness and three golf courses with different age. Landscape zone is remarkably heterogeneous versus other microhabitats (fairway and woodland) and the heterogeneity of tree communities amongst the three courses is relatively weak. Synergistic operation of natural regeneration (natural legacy effect) and anthropogenic management (anthropogenic legacy effect) has fostered diversity accumulation. On the one hand, temporal changes in landscape fashion through a century and variations in site management have driven and maintained species diversity. On the other hand, the founder effect of inherited and cultivated species, as well as successful invasion and establishment of native species, have imposed floristic imprint and inertia on woodland habitat. The findings suggested that urban golf courses can serve as potential hotspots for biodiversity conservation within urban ecosystems. [ABSTRACT FROM AUTHOR]

Fast urbanization has led to ozone (O 3 ) being the main pollutant in summer in most of China. To assess future ground-level O 3 effects on the service of urban greening species and clarify the underlying mechanism of O 3 damage, four common urban greening species, Ailanthus altissima (AA), Fraxinus chinensis (FC), Platanus orientalis (PO) and Robinia pseudoacacia (RP) were exposed to non-filtered air (NF) and to elevated O 3 (E-O 3 ) in open-top chambers. E-O 3 induced visible injury in all species as well as microscopic alterations such as collapse of the palisade parenchyma cells, callose accumulation, or chloroplast and mitochondrial accelerated senescence. E-O 3 significantly reduced light-saturated CO 2 assimilation ( A sat ), the maximum activity of Rubisco ( Vc max ), the maximum electron transport rate ( J max ), and fluorescence parameters such as the quantum yield of noncyclic electron transport ( ϕ PSII ), and the quenching of photochemical efficiency of PSII ( q P). It also increased total antioxidant capacity, phenolics and ascorbate contents. No significant interaction between O 3 and species was found in photosynthetic performance and antioxidant systems, suggesting that the four species selected were sensitive to O 3 . Of all four species, AA was the most sensitive species due to a combination of earlier injury onset, anatomical features, lower antioxidant responses and higher stomatal conductance. The sensitivity of tree species to O 3 is a factor to be considered for urban greening. Ozone may affect important urban forest ecosystem services by reducing CO 2 assimilation. [ABSTRACT FROM AUTHOR]

• Significant differences in surface regional heat island intensity between cities of different climate types. • 3D urban morphology effectively improve the interpretation of surface regional heat island intensity. • Trees have a more significant cooling effect than the rest of the green space types. • Green to gray facility area or volume ratio has cooling effect limitations. Urban heat islands (UHIs) exert a substantially negative impact on human health and urban sustainability. The role of two-dimensional (2D) landscape patterns in UHIs are well documented; while the effects and contributions of three-dimensional (3D) urban structures remain unclear, especially across different climatic zones. Here we investigated the relationship between 2D/3D urban morphology and the urban thermal environment in summer and winter during the day and at night in 62 representative large cities across four major climate zones in China. First, we extracted the seasonal surface regional heat island intensity (SRHII) using the MODIS 8-Day land surface temperature product. Subsequently, we constructed 25 2D and five 3D urban features and explored their relative importance and respective roles in UHIs in different climatic contexts. Results show that: (1) significant differences (p < 0.05) exist in SRHII between various climate zones; cities with a humid subtropical climate experience temperatures approximately 2 °C higher during the day in summer compared to those with the other climate types. (2) 3D urban features can effectively improve the interpretation of urban features for SRHII, with an average optimization level of 21%. (3) Urban trees have a higher cooling effect than other green spaces, whereas tall buildings can also reduce the UHI effect. (4) On summer days, equal proportions of tree to building volume provide the greatest cooling effects. This study provides new insights into the effect of 3D urban characteristics on SRHII and has promising implications for climate resilience planning and heat-related risk management [ABSTRACT FROM AUTHOR]

Dust pollution in Oasis cities located in arid areas affect resident's body, life and work in long term . The present study examined dust deposition on single leaves of Populus alba L. var. pyramidalis (Bunge) at various heights (1m, 2m, 4m), analysed dust particle size distribution and its contents in arid area city-Aksu, northwest China. The results showed that the amount of dust retained per leaf area of Populus alba L. var. pyramidalis (Bunge) differed significantly between sites, as follows: CAT>IA>P>RA>SFA; Leaves at a height of 1 meter retain the most dust compared with other two heights, as follows: 1m > 2m > 4m. Dust particles larger than PM10 account for more than 90% of all dust particles in all the sites and the dust accumulated on tree leaves is mainly of local urban origin. The variation of heavy metal concentrations in different sites is significant. [ABSTRACT FROM AUTHOR]

Street-side vegetation greenery contributes substantial health benefits for pedestrians. Multi-year street view images are expected to enable the monitoring of dynamic street-side vegetation greenery changes and the development of targeted urban landscape plans. However, the potential of multi-year street view images used for the assessment of street-side vegetation greenery has not been evaluated yet. Besides, complicated urban landscapes may make it difficult to accurately quantify vegetation greenery. This study developed a framework to assess the spatio-temporal variation of street-side vegetation greenery using the Baidu Street View images and a new Vegetation Greenery Index (VGI). The proposed analytical framework was applied to Tai'an city, a highly populated city where urbanization has been rapid in China. The level of vegetation greenery estimated using the proposed framework was compared with ground truths randomly collected at sampling sites along the road networks in 2014 and 2019 to assess the applicability. Results demonstrated that the proposed VGI method could accurately quantify street-side vegetation greenery. The comparison of multi-year VGI layers could identify locations where vegetation greenery substantially changed and quantify the overall change in urban greenery. Vegetation greenery estimates were well agreed with the ground truths. Spatio-temporal variations in the urban vegetation greenery were attributed to trees that were newly planted or removed, the natural growth of the existing vegetation, and new building construction. The proposed framework is expected to be a useful tool to evaluate urban vegetation greenery and help urban landscape planning. [ABSTRACT FROM AUTHOR]

The emergence of various types of everyday urban problems poses severe challenges to the conventional top-down designed urban problem-handling protocols. Social sensing data, such as the urban problem complaint hotline records, constitute good sources for collecting bottom-up information on urban problems. Nevertheless, a partially obsolete urban problem categorization standard, a manually operated and experience-dependent workflow for problem classification and pushing, and an unoptimized problem-handling responsibility designation among the municipal departments have been impairing the sufficient utilization of the collected complaint data toward more efficient urban problem-handling performance. In this paper, based on the 12345-hotline data collected in Sanya City, China, we 1) construct an urban problem tree that presents a new and expandable classification of everyday urban problems with 7 super-types, 34 types, and 105 sub-types of events, thus complementing that in the existing National Standard which merely contains 6 types and 66 sub-types; 2) design an auto-classification algorithm for the complaint records with Natural Language Processing and Supervised Machine Learning methods, which achieves an accuracy of up to 75% at the super-type level; and 3) optimize the urban problem-handling responsibility designation among the municipal departments for improved departmental function distinction and balanced workloads, which combined with the auto-classification algorithm yield a decrease of the problem pushing failure ratio from the current 73.8% to 14.6%. We integrate all the above functions in a web-based information system to establish a digital platform for practical urban problem-handling. We conclude the paper with discussions on the paper's implications of an overhaul of urban legislative and executive systems following a bottom-up paradigm and reflections on the paper's limitations and theoretical implications from a complex-system theory perspective. • An urban problem tree constructed from the "12345" Hotline is a complement to the National Standard. • Developing NLP and supervised ML algorithms for effective classification of crowd-sourced hotline complaints. • Optimizing the local government structure for urban problem-handling from a bottom-up approach. • Implementing a web-based system for hotline handling which decreases the failed pushes from 73.8% to 14.6%. [ABSTRACT FROM AUTHOR]

To understand effects of tree seasonal characteristics on pedestrian thermal-visual perception and explore their influence on outdoor thermal comfort, four typical deciduous shade trees, local to Xi'an China, were measured for annual crown characteristics. Meteorological variables and pedestrian thermal and visual perceptions were simultaneously collected. Universal Thermal Climate Index (UTCI) and visual conditions were used to stratify our results. We found that: (1) Neutral UTCI (NUTCI) under trees decreased in order of G. biloba , P. orientalis , Y. denudat a and M. azedarach. (2) The ability of trees to reduce UTCI was related to leaflet area, crown color (degree of red and green [a*] and brightness of the color [L*]) and diffuse non-interception (DIFN). The thermal sensation vote (TSV) reduction was related to crown vertical projected area (A crown) and L*. (3) The ability of trees to reduce the illumination intensity was related to A crown , DIFN and L*, and the sun sensation vote (SSV) reduction was related to L*. (4) NUTCI in the environment with high illumination was lower than that with low illumination. When UTCI was 1°C−37 °C, respondents who reported 'slightly bright to too bright' primarily perceived a neutral thermal sensation, followed by these who felt 'neutral' and 'slightly dark to too dark'. Respondents who reported high aesthetic assessment scores tended to vote warm TSV in winter. Our results could provide selection baselines for urban shade trees in optimizing overall pedestrian comfort and promoting urban livability. [Display omitted] • Effects of tree characteristics on thermal-visual perception in Xi'an, China were investigated. • The ability of trees to reduce UTCI was related to leaflet area, crown color and DIFN. • The ability of trees to reduce illumination was related to crown vertical projected area, DIFN and crown color. • Respondents who reported 'slightly bright to too bright' primarily perceived a neutral thermal sensation. • Respondents who reported high aesthetic assessment scores tended to vote warm TSV in winter. [ABSTRACT FROM AUTHOR]