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Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition

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A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Urban Forestry".

Deadline for manuscript submissions: 31 July 2025 | Viewed by 15607

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Dr. Jose Luis Santiago

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Atmospheric Modelling Unit, Environmental Department, Research Center for Energy, Environment and Technology (CIEMAT), 28040 Madrid, Spain
Interests: urban air quality; microscale modeling; in particular with computational fluid dynamics (CFD) models; urban vegetation (trees in streets, vegetation barriers, etc.) and its effects on pollutant concentrations and thermal comfort; pollutant mitigation strategies; urban climate and meteorology
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Dr. Esther Rivas

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Atmospheric Pollution Division, Environmental Department, Environment and Technology (CIEMAT), 28040 Madrid, Spain
Interests: CFD methodologies; numerical model evaluation and validation; pollutant dispersion and heat transfer phenomena; urban planning; air quality and energy efficiency
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Dr. Beatriz Sanchez

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Guest Editor

Atmospheric Modelling Unit, Department of Environment, CIEMAT, 28040 Madrid, Spain
Interests: meteorological micro and mesoscale modeling; CFD models; WRF model; urban climate; urban air quality; air pollution and heat mitigation strategies in cities
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The interaction of the atmosphere with urban surfaces (buildings, vegetation, etc.) induces complex flow patterns and a reduction in ventilation on the streets. This fact, linked with pollutant emissions (e.g., traffic emissions) gives rise to air quality problems in cities. In addition, the thermal properties of urban materials (buildings, roads) often cause elevated air temperature that leads to thermal discomfort for people. To mitigate these problems, nature-based solutions are widely used, but more knowledge about the complex effects of different types of green infrastructures is needed to design effective strategies for renaturing urban environments.

In this Special Issue, we invite original research articles relating to the impact of urban vegetation on air quality and local climate in urban environments. These contributions will include modeling studies at a micro- and meso-scale (e.g., computational fluid dynamics model, urban canopy models or mesoscale models) and experimental works from field and laboratory experiments. Urban green infrastructures such as different configurations of trees in the streets, urban parks or vegetation barriers will be investigated in relation to their effects on pollutant concentration (aerodynamic effects, pollutant deposition, biogenic emissions, etc.) and/or on local climate and thermal comfort (transpirational cooling, shading, etc.). In addition, works on new parameterization of the effects on urban vegetation are also welcomed. We also invite review papers focusing on the current knowledge and future studies on this topic.

Dr. Jose Luis Santiago
Dr. Esther Rivas
Dr. Beatriz Sanchez
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

urban air quality and climate
thermal comfort
urban vegetation
trees in the streets
urban forests
vegetation barriers
urban parks
nature-based solutions

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Published Papers (9 papers)

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Editorial

Jump to: Research

4 pages, 687 KiB

Open AccessEditorial

Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—Series II

by Esther Rivas, Jose-Luis Santiago and Beatriz Sánchez

Forests 2023, 14(2), 284; https://doi.org/10.3390/f14020284 - 1 Feb 2023

Cited by 2 | Viewed by 1547

Abstract

Cities are composed of different types of urban obstacles such as buildings, cars, trees, hedgerows, etc [...] Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

Research

Jump to: Editorial

21 pages, 12559 KiB

Open AccessArticle

The Impact of Meteorological Factors and Canopy Structure on PM_2.5 Dynamics Under Different Urban Functional Zones in a Subtropical City

by Yichen Huang, Yue Cai, Jiejie Jiao, Chunyu Pan, Guangyu Wang, Chong Li, Zichen Jia, Zhihao Chen, Yufeng Zhou and Guomo Zhou

Forests 2025, 16(3), 479; https://doi.org/10.3390/f16030479 - 9 Mar 2025

Viewed by 880

Abstract

PM_2.5 pollution has intensified with rapid urbanization and industrialization, raising concerns about its health and environmental impacts. Both meteorological factors and urban forests play crucial roles in influencing PM_2.5 concentrations. However, limited attention has been given to the direct impact of canopy structure on PM_2.5 levels at a larger scale. This study analyzes the temporal variation of PM_2.5, including seasonal and diurnal patterns, across different functional zones (park, traffic, and residential zones) in a subtropical region. It also investigates the seasonal responses of PM_2.5 to meteorological factors (temperature, humidity, and precipitation) and canopy structure characteristics, including canopy diameter (CD), canopy thickness (CT), canopy area (CA), canopy volume (CV), canopy height ratio (CH), leaf area index (LAI), and tree canopy cover (CO). The results show that among different functional zones, PM_2.5 concentrations were the highest in park zones, followed by traffic zones. Seasonal variations in PM_2.5 concentrations were the highest in winter (84.00 ± 45.97 μg/m³), with greater fluctuations, and the lowest in summer (36.85 ± 17.63 μg/m³ µg/m³), with smaller fluctuations. Diurnal variation followed an “N”-shaped curve in spring, summer, and autumn, while a “W”-shaped curve was observed in winter. Correlation analysis indicated significant negative correlations between PM_2.5 and humidity, temperature, and rainfall, while CD, CA, and CV showed positive correlations with PM_2.5. Notably, PM_2.5 exhibited greater sensitivity to changes in canopy structure in winter, followed by autumn. Despite these findings, the influence of canopy structure on PM_2.5 concentrations was considerably smaller compared to meteorological factors. In particular, every 1 m² increase in canopy area could raise PM_2.5 levels by 0.864 μg/m³, whereas an average increase of 1 mm in rainfall could raise PM_2.5 by 13.665 μg/m³. These findings provide valuable guidance for implementing protective measures, improving air quality, optimizing urban greening strategies, and enhancing public health outcomes. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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25 pages, 21504 KiB

Open AccessArticle

Impacts of Plant Configuration on the Outdoor Wind Comfort of Subtropical Coastal Campuses: Evidence from a Study of Quanzhou

by Jing Chen, Jiushan Zeng, Tiantian Huang, Yaolong Wang, Haosen Yang, Xiaofang Yu and Zefa Wang

Forests 2025, 16(3), 461; https://doi.org/10.3390/f16030461 - 5 Mar 2025

Cited by 2 | Viewed by 516

Abstract

Even though the interaction between plants and the outdoor wind environment has been a focus of interest for scholars from various disciplines in recent years, the relationship between campus outdoor wind comfort and plant configuration in subtropical coastal areas remains poorly understood. Using the outdoor space of a typical subtropical coastal campus (the Donghai Campus of Quanzhou Normal University) as a case study, we explore the connection between plant configuration and outdoor wind comfort. The campus outdoor area is segmented into roads, squares, and courtyards to investigate this relationship. To achieve this goal, a 9-h fixed-point measurement method and the PHOENICS software (2016) were utilized. The following are the findings of the research: (1) Within the realm of trees, the banyan, Bischofia javanica, and kapok species exhibit a notable impact on wind speed reduction, with respective wind reduction ratios of 1.22, 1.31, and 1.29. Notably, among shrubs, waringin stands out with a wind reduction ratio of 1.83. (2) The tree + shrub + grass combination is the most effective method for reducing wind among the three plant facade configurations. Specifically, the combination of Bischofia javanica, waringin, and carpet grass has the best wind reduction effect, with a wind reduction ratio of 2.55. (3) Adding Bischofia javanica, waringin, and grass plants in areas with high wind speeds can effectively improve wind comfort. This provides directions for creating a comfortable wind environment on university campuses situated in subtropical coastal areas. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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23 pages, 5811 KiB

Open AccessArticle

Factors Affecting Dust Retention in Urban Parks Across Site and Vegetation Community Scales

by Xiang Zhang, Chuanwen Wang, Jiangshuo Guo, Zhongzhen Zhu, Zihan Xi, Xiaohan Li, Ling Qiu and Tian Gao

Forests 2024, 15(12), 2136; https://doi.org/10.3390/f15122136 - 2 Dec 2024

Viewed by 1328

Abstract

Air pollution poses a significant threat to human health, especially in urban areas. Urban parks function as natural biofilters, and examining the factors influencing dust retention—specifically PM2.5 and PM10 concentrations—across different spatial scales can enhance air quality and resident well-being. This study investigates the factors affecting dust retention in urban parks at both the site and vegetation community scales, focusing on Xi’an Expo Park. Through on-site measurements and a land use regression (LUR) model, the spatial and temporal distributions of PM2.5 and PM10 concentrations were analyzed. The indications of the findings are as follows. (1) The LUR model effectively predicts factors influencing PM2.5 and PM10 concentrations at the site scale, with adjusted R² values ranging from 0.482 to 0.888 for PM2.5 and 0.505 to 0.88 for PM10. Significant correlations were found between particulate matter concentrations and factors such as the distance from factories, sampling area size, distance from main roads, presence of green spaces, and extent of hard pavements. (2) At the plant community scale, half-closed (30%–70% canopy cover), single-layered green spaces demonstrated the superior regulation of PM2.5 and PM10 concentrations. Specifically, two vegetation structures—the half-closed single-layered mixed broadleaf-conifer woodland (H1M) and the half-closed single-layered broad-leaved woodland (H1B)—exhibited the highest dust-retention capacities. (3) PM2.5 and PM10 concentrations were highest in winter, followed by spring and autumn, with the lowest levels recorded in summer. Daily particulate matter concentrations peaked between 8:00 and 10:00 a.m. and gradually decreased, reaching a minimum between 4:00 and 6:00 p.m. The objective of this study is to evaluate the impact of urban green spaces on particulate matter (PM) concentrations across multiple scales. By identifying and synthesizing key indicators at these various scales, the research aims to develop effective design strategies for urban green spaces and offer a robust theoretical framework to support the creation of healthier cities. This multi-scale perspective deepens our understanding of how urban planning and landscape architecture can play a critical role in mitigating air pollution and promoting public health. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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14 pages, 3200 KiB

Open AccessArticle

The Added Value of Urban Trees (Tilia tomentosa Moench, Fraxinus excelsior L. and Pinus nigra J.F. Arnold) in Terms of Air Pollutant Removal

by Slaveya Petrova

Forests 2024, 15(6), 1034; https://doi.org/10.3390/f15061034 - 14 Jun 2024

Cited by 1 | Viewed by 1052

Abstract

The serious densification of human settlements necessitates an increase in the role and importance of green infrastructures in the overall functioning of urban ecosystems. Accordingly, the aim of the present study was to (1) assess the efficiency of air pollutant removal (potentially toxic elements) of three common ornamental trees (Tilia tomentosa Moench, Fraxinus excelsior L. and Pinus nigra J.F. Arnold) and (2) model the air quality regulatory services (removal of PM₁₀, PM_2.5 and NO₂). Three different approaches were applied—enrichment factor (EF) and metal accumulation factor (MAI) per tree species, as well as simulation modeling for the whole urban forest. The MAI values of the three studied species were found to be very similar, in the range of 22.35 to 23.08, which suggests that these species could be a good choice for planting in urban areas with worsened air quality. The highest EF values were observed for U (3–18), followed by As (1.6–2.56) and Sr (0.87–2.46). The potential of urban forests in countering air pollution was highlighted by three simulated scenarios for PM₁₀, PM_2.5 and NO₂ removal. The highest removal efficiency was calculated for evergreen species, followed by the mixed composition of deciduous (90%) and evergreen trees (10%), and the scenario with wholly deciduous trees had the lowest one. The contribution of nature-based solutions in meeting air quality standards and enhancing resilience in urban areas was clearly demonstrated. The functional complementarity of the different functional tree groups (coniferous, evergreen and deciduous broad-leaved species) was proven to be crucial for the support of both functional stabilities of the phytocenosis under diverse climatic conditions and during the change of seasonal cycles in the vegetation. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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14 pages, 1481 KiB

Open AccessArticle

Nature-Based Solutions to Reduce Air Pollution: A Case Study from Plovdiv, Bulgaria, Using Trees, Herbs, Mosses and Lichens

by Slaveya Petrova, Iliana Velcheva and Bogdan Nikolov

Forests 2024, 15(6), 928; https://doi.org/10.3390/f15060928 - 26 May 2024

Cited by 3 | Viewed by 2670

Abstract

Nature-based solutions (NBSs) are becoming more and more recognized as useful instruments to address the challenges that urban areas are currently facing, i.e., climate change adaptation, flood mitigation, etc. In the present study, we aimed to: (1) compare the efficiency of mosses, lichens, herbs and trees in removing pollutants from the urban air using their biomonitoring potential; (2) assess their efficiency as nature-based solutions to mitigate urban air pollution; and (3) propose a framework for implementing such NBSs in urban areas. The first step involved analyses of the concentrations of 20 potentially toxic elements in eight selected biomonitors. After that, an assessment of their removal capacity was made on the basis of elements accumulation. This is the first complex study in an urban area involving the simultaneous application of organisms of eight different species and four different systematic groups (lichenized fungi, mosses, herbaceous plants, woody species) as well as such a large number of potentially hazardous elements. The present study sheds new light on some well-known biomonitors in the context of their application for air pollution mitigation. The great potential of the eight studied plant species for efficient removal of potentially toxic elements is highlighted and their implementation into NBS frameworks is recommended. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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23 pages, 43890 KiB

Open AccessArticle

A Study on the Effect of Green Plot Ratio (GPR) on Urban Heat Island Intensity and Outdoor Thermal Comfort in Residential Areas

by Jian Zheng, Zilong Li and Bohong Zheng

Forests 2024, 15(3), 518; https://doi.org/10.3390/f15030518 - 11 Mar 2024

Cited by 8 | Viewed by 2457

Abstract

Greenery impacts the urban thermal environment, but the benefits of the three-dimensional green volume of space have not been effectively evaluated. In this paper, we analyzed the impact of 3D greenery on urban heat island intensity and thermal comfort in residential areas from the perspective of the green plot ratio (GPR). We selected a typical residential area, set up simulation models, and then analyzed the effect of different GPR values on the outdoor thermal environment using the validated ENVI-MET simulation. The results showed that increasing GPR in residential areas can effectively reduce the intensity of urban heat island and improve thermal comfort. When the GPR reaches 0.5 and 1.5, the thermal comfort level of the building overhead space and the north–south street space decreases from “very strong thermal stress” to “strong thermal stress”. When the GPR reaches 2.5, the outdoor thermal comfort of the east–west street space and courtyard space is reduced to “hot”. When the GPR is higher than 0.5, the urban heat island intensity in the north–south street space decreases by one level, from “very strong” to “strong”. When the GPR reaches 3.5, all four types of spaces have “moderate” urban heat island intensity. Increased GPR exacerbates urban heat island intensity to some extent and worsens outdoor thermal comfort due to the nocturnal insulating effect of plants. Based on the results, the study proposes the bottom-line control of the GPR index from the perspective of urban heat island mitigation and thermal comfort improvement. This paper points out the benefits of GPR in residential areas in improving the human environment, which is of great practical value for developing urban residential environment from “increasing quantity” to “improving quality”. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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26 pages, 4664 KiB

Open AccessArticle

A Simulation Study of the Impact of Urban Street Greening on the Thermal Comfort in Street Canyons on Hot and Cold Days

by Junyou Liu, Bohong Zheng and Fan Yang

Forests 2023, 14(11), 2256; https://doi.org/10.3390/f14112256 - 16 Nov 2023

Cited by 1 | Viewed by 1977

Abstract

The urban heat island effect has become a widely concerning issue worldwide. Many researchers have made great efforts to improve the summer thermal comfort of urban street canyons by optimizing street greening. Relatively less research has focused on how to improve the thermal comfort of street canyons by optimizing street greening during cold days. Many researchers have proposed strategies to improve the summer thermal comfort of street canyons using road greening. This may have a significant negative impact on the winter thermal comfort of street canyons due to the lack of consideration of the impact on hot and cold days simultaneously, especially when the road green space is mainly composed of evergreen tree species. We aimed to explore the impacts of urban street greening on thermal comfort on hot and cold days at the same time. We used Zhutang West Road in Changsha, China, as an example and built six different models to explore the impacts of the street vegetation types, number of street trees, tree heights, crown widths, and Leaf Area Index on the thermal comfort of the street canyon. In addition, we also considered the impact of different building features and wind directions on the thermal comfort of the street canyon. We employed ENVI-met (version 5.5.1) to simulate different urban street greening models. The results show that the model with a high tree canopy density, tall trees, large and dense crowns, and sufficient building shade has good thermal comfort on hot days (the average physiological equivalent temperature (PET) is 31.1 °C for the study period) and bad thermal comfort on cold days (the PET is 13.3 °C) when it is compared with the other models (the average PETs are 36.2 °C, 31.5 °C, 41.5 °C, 36.2 °C, and 35.5 °C, respectively, on hot days and for other models). In addition, the model with a very large number of short hedges has a positive impact on thermal comfort during hot days (the PET is 31.1 °C). The PET value of another comparable model which does not have hedges is 31.5 °C. Even if the model with a small building area has good ventilation, the small building shade area in the model has a more obvious impact and the model has relatively good thermal comfort during cold days (the PET is 14.2 °C) when it is compared to models with bigger building areas (the PET is 13.9 °C). In summer, when the wind is parallel to the direction of the street canyon, the wind speed in the street canyon is high and the model has relatively good thermal comfort (the PET is 35.5 °C) compared with another model which has different wind direction and lower wind speed at the street canyon (the PET is 36.2 °C). In winter, when the wind is perpendicular to the direction of the street canyon, buildings and trees have a strong windproof effect and this is beneficial to the improvement of thermal comfort (the PET is 15.3 °C for this model and 13.9 °C for another comparable model). This research lays a solid foundation and encourages people to think about the impact of building and tree composition and configuration on the thermal comfort of street canyons during hot and cold days simultaneously. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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18 pages, 4739 KiB

Open AccessArticle

Response of Common Garden Plant Leaf Traits to Air Pollution in Urban Parks of Suzhou City (China)

by Zhiyu Yang, Xing Zhang, Yanting Qu, Fei Gao and Yutong Li

Forests 2023, 14(11), 2253; https://doi.org/10.3390/f14112253 - 16 Nov 2023

Cited by 6 | Viewed by 1846

Abstract

In this study, to comprehensively investigate the impact of garden plants on air quality, we measured the leaves of 18 common garden plants in three different areas, namely, Suzhou industrial parks (clean air area (CAA)), Xiangcheng district parks (lightly polluted area (LPA)), and Huqiu district parks (highly polluted area (HPA)). We also measured the leaf functional traits of different life-types of plants. To explore the trade-off strategies of the leaf traits of common garden plants in response to air pollution and to assess the adaptive capacity of different life types of plants to air pollution. The results show that plants in the polluted area had higher leaf dry matter content (LDMC) and leaf nitrogen content per unit mass (N_mass), and a lower specific leaf area (SLA), maximum net photosynthetic rate per unit area (A_area), transpiration rate (Tr), stomatal conductance (Gs), and chlorophyll value (SPAD). Pearson correlation analysis showed that SLA was significantly positively correlated with N_mass, Tr, photosynthetic use efficiency (PNUE), and SPAD, and significantly negatively correlated with LDMC, while A_area was significantly positively correlated with chlorophyll value. Redundancy analysis revealed that the correlation between each leaf functional trait and atmospheric pollution factors was as follows: LDMC > N_mass > SLA > LA > A_area > Tr > PNUE > SPAD. The results suggest that different plant types have varying levels of adaptability to environmental conditions. Trees were found to be the most adaptable, followed by shrubs, herbs, and lianas. Additionally, under the stress of air pollution, herbs and lianas exhibited characteristics of “fast investment-return” on the leaf economic spectrum, meaning they were able to quickly allocate resources to maximize their return. However, trees and shrubs displayed traits of “slow investment-return”, indicating a more conservative approach to resource allocation. These results provide valuable insights into the leaf trade-off strategies of plants in Suzhou Park under air pollution stress and can guide the selection of suitable plant species in similar environments. Full article

(This article belongs to the Special Issue Advances on the Influence of Vegetation and Forest on Urban Air Quality and Thermal Comfort—2nd Edition)

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