Characteristics of vegetation shading and transpiration cooling effects during hot summer

Xiaojuan, 王晓娟 Wang; Fanhua, 孔繁花 Kong; Haiwei, 尹海伟 Yin; Hailong, 徐海龙 Xu; Junsheng, 李俊生 Li; Yingxia, 蒲英霞 Pu

doi:10.5846/stxb201712032173

Cited by 2 publications

(3 citation statements)

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“…A previous study indicated the varying effects of three tree species on microclimate by examining the changing of sap flow, with the cooling effect order being Populus simonii > Cedrus deodara > C. camphora. This was attributed to the differences in the volume of the canopy transpiration cooling effect (Wang et al, 2018).…”

Section: Effects Of Urban Trees On Microclimatic Conditionsmentioning

confidence: 99%

“…This finding was consistent with that of Xia et al (2021), who investigated the possibility that C. camphora could improve air humidity and found that C. camphora was sensitive to changes in water conditions. Wang et al (2018) investigated the effect of green spaces on mitigating temperatures through evapotranspiration during the night and providing shade during the daytime. The results showed that the contribution (60%-75%) to reducing temperatures during the daytime by providing canopy shade was significantly greater than the contribution (25%-40%) made by evapotranspiration.…”

Section: The Internal Correlation Mechanisms Between Physiological Ch...mentioning

confidence: 99%

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Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas

Feng

Huang²,

He³

et al. 2023

Front. Environ. Sci.

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Purpose: Urban trees play a key role in ameliorating extreme urban climates in cities. At the micro-level, it is crucial to investigate the variations in microclimates affected by the canopies of different tree species. The significance of this research is to provide scientific evidence for the selection of tree species in urban planning that can improve the local microclimate. This study examines the factors of microclimate (air temperature, relative humidity, wind environment, and solar radiation) underneath the canopy of four different evergreen tree species in hot and humid areas. Furthermore, the correlation between the physiological characteristics of these tree species and microclimate was statistically analyzed using data on the physiological parameters of the trees and microclimate factors.Methods: In this study, four tree species were selected for field measurements: Ficus microcarpa L. f., Ficus virens Aiton, Bauhinia x blakeana Dunn, and Cinnamomum camphora (L.) Presl. We used the HOBE (H21-0024, onset) to measure three climatic parameters (Temperature, Relative Humidity, and Instantaneous Wind Speed), and the Li-6400 Portable Photosynthesis System to measure five plant physiological parameters: Stomatal Conductance (Gs), Leaf Temperature (Tleaf), Leaf Surface Relative Humidity (RHsfc), Photosynthetically Active Radiation (PAR), and Leaf-level Vapor Pressure Deficit (Vpdl). The observations were conducted during winter (January 16 - January 22) and summer (August 7 - August 22). The investigation periods were 9:00–11:00, 12:00–14:00, and 16:00–18:00, and data were recorded at 15-min intervals. The observational data obtained were analyzed using statistical methods, including one-way analysis of variance, Pearson correlation coefficient, and multiple regression analysis.Results: The results of this study indicated that the four tree species being measured had different effects on the microclimate at the sites in both the winter and summer seasons. During the 7-day observation in the summer, the cooling effect of the four tree species was significant. The relative humidity underneath the canopies was 3%–11% higher than that of weather stations. The instantaneous wind speed in the afternoon was relatively higher than at other times. The solar radiation intensity was dramatically reduced by 85%–95%. During the 7-day observation in the winter, the trees had a warming effect in the morning. The relative humidity underneath the canopies was 10%–20% higher than that of the weather stations. The areas underneath the canopies were windless in the afternoon. The solar radiation intensity was reduced by 78%–95%. Ficus microcarpa was found to be one of the most effective tree species for increasing the relative humidity and reducing solar radiation intensity in hot and humid areas. Additionally, the highest instantaneous wind speed was observed in the areas underneath the canopies of F. virens and C. camphora. Statistical tests revealed that the air temperature and the instantaneous wind were extremely significantly correlated with Tleaf and RHsfc.Conclusion: The four urban tree species studied had varying degrees of effect on air temperature, relative humidity, wind speed, and reducing solar radiation intensity in the areas underneath their canopies. Furthermore, these trees demonstrated varying abilities to improve microclimate conditions in different seasons. The four trees had a cooling effect in the summer. The instantaneous wind speed was calm in the afternoons during the winter in contrast to being relatively high speed in the afternoons during the summer. This characteristic is beneficial to warmth in winter and coolness in summer. In terms of the internal influence mechanisms, the results of the analysis indicated that microclimate factors were significantly correlated with the physiological parameters of the trees. Tleaf, RHsfc, and Vpdl were significant physiological parameters and had different contribution rates to microclimate factors.

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Section: Effects Of Urban Trees On Microclimatic Conditionsmentioning

confidence: 99%

Section: The Internal Correlation Mechanisms Between Physiological Ch...mentioning

confidence: 99%

Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas

Feng

Huang²,

He³

et al. 2023

Front. Environ. Sci.

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“…Previous research has indicated that green vegetation in urban parks converts a large amount of heat into water vapor through transpiration, releasing it into the atmosphere. Additionally, vegetation can shield and reflect a significant portion of solar radiation, thereby maintaining lower surface temperatures [10]. Natural or artificial water bodies such as lakes, rivers, or ponds can absorb and release considerable heat, exerting strong temperature regulation effects [11].…”

Section: Introductionmentioning

confidence: 99%

Spatial Gradient Differences in the Cooling Island Effect and Influencing Factors of Urban Park Green Spaces in Beijing

Xu,

Wang,

Zhu

2024

Buildings

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Urban park green spaces exhibit significant cool island effects, which can effectively mitigate the urban heat environment. Clarifying the characteristics and differences in the cool island effects of urban parks across different spatial gradients within cities is instrumental in identifying potential issues and optimizing the structure and resource allocation of park green spaces in a scientifically rational manner. This study focuses on parks within the central urban area of Beijing, utilizing remote sensing image interpretation and land surface temperature (LST) inversion to extract relevant characteristics of park green spaces and the park cool island intensity (PCI) index. Various mathematical and statistical methods including correlation analysis, regression analysis, and cluster analysis are employed to conduct comparative studies across three gradients: within the 3rd ring road, between the 3rd and 5th ring roads, and outside the 5th ring road. The analysis reveals that both park green space characteristics and urban heat island effects exhibit spatial gradient differences, collectively influencing the cool island effects of urban park green spaces. PCI gradually decreases across the three spatial gradients. Cluster analysis identifies four distinct types of parks with different cool island effect characteristics, highlighting the need for optimization and improvement in over half of the parks. Various indicators of park green space characteristics show different correlations with PCI, with variations in correlation strength and thresholds across gradients. The fitting effects of regression equations for each characteristic indicator and PCI gradually worsen from within the 3rd ring road to outside the 5th ring road, with different factors playing important roles across gradients. This study enhances our understanding of the cool island effects of urban park green spaces and facilitates the proposition of differentiated optimization management strategies for urban park green space planning and system construction in different regions.

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Characteristics of vegetation shading and transpiration cooling effects during hot summer

Cited by 2 publications

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Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas

Microclimate effects and influential mechanisms of four urban tree species underneath the canopy in hot and humid areas

Spatial Gradient Differences in the Cooling Island Effect and Influencing Factors of Urban Park Green Spaces in Beijing

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