Objective In highly urbanized areas, the widespread presence of urban heat island (UHI) effect is not conducive to sustainable urban development and quality improvement of urban living environment. As part of urban green infrastructure, urban green space can not only reduce and improve the scope and intensity of UHI, but also further improve the human comfort of small-scale urban spaces. At the same time, the functions of urban green spaces vary due to their landscape pattern characteristics and plant community characteristics. This research aims to innovatively elucidate the correlation between the spatial characteristics of plant community and human thermal comfort (HTC) in urban green space based on long-term fixed-point measurement data.
Methods This research covers the early planning and design stage, construction stage, and post-construction use stage of Beijing Olympic Forest Park (BOFP) spanning the period from 2005 to 2022. The research team not only participates in the planning and design of BOFP, but also pays continuous attention to the effectiveness and efficiency of the park’s ecological benefits after being completed and put into operation. Specifically, the research team continuously measures the basic data on HTC, such as air temperature and relative humidity, in 17 fixed sample plot areas of BOFP. Through preliminary analysis of measured data, it is found that there are significant differences in HTC between different plant community structures and types of areas within BOFP during the same period. This is not only an important opportunity for this research to be conducted, but also constitutes the core scientific issue that this research attempts to elucidate. This research is based on measured data and attempts to use the PMV-PPD model of HTC that takes into account both subjective and objective factors to analyze and explain the spatial differentiation characteristics of HTC in BOFP.
Results The research results indicate that the HTC level of different community structures is highest in the tree − shrub and tree − grass/ground cover plant community structure area, intermediate in the grass/ground cover and shrub − grass/ground cover area, and lowest in the tree − shrub − grass/ground cover plant community structure area in BOFP. The HTC level of different plant community types is highest in the deciduous broad-leaved plant community area, followed by the evergreen coniferous plant community area, mixed coniferous broad-leaved plant community area, and grass/ground cover area. And the HTC level is lowest in the shrub area. The reason for this result may be that the direct solar radiation in the upper layer of the sample plot area, where deciduous broad-leaved plant community is the dominant plant community, is obstructed by the canopy layer and further forms a temperature difference between the upper and lower layers of the canopy (the canopy density of this plant community type area is higher than that of other types). Moreover, the relatively spacious space between the lower layer, shrubs and grass/ground cover plants possibly enables the horizontal and vertical flow of air. However, this feature of other plant community types is not yet available, and further in-depth attention is still needed. The HTC level of the double-layer plant community structure area is significantly higher than that of the multi-layer plant community structure/waterfront plant community area and the single-layer plant community structure/waterfront square area in BOFP.
Conclusion BOFP is an artificial plant park built following the principles of plant community composition in natural areas (shallow mountain and plain areas in Beijing). The planning, design and construction process of BOFP is also a process of practicing the design principle of “nature imitation” that has invariably been followed by Chinese landscape architecture. What are the results of this process? Scientific experiment and analysis are needed to provide feedback on and verification of this process. Since 2005, the plant community structures and typical types of areas in BOFP have been recorded in detail, including such information as three-dimensional green volume, and canopy density of plant communities that involves individual plant height, diameter, crown width, etc. Moreover, the micro-environmental indicators represented by physical comfort have been continuously measured, recorded and analyzed. The aforesaid process is actually a test and empirical process of the ecological benefits brought by “nature imitation”. The research results may provide scientific basis for the planning, design, and renewal of urban green spaces aimed at improving urban environmental comfort.
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