城市绿地的生态环境效应研究进展

工业化的快速发展和城市化进程的加剧,使得城市生态环境的破坏和污染愈来愈严重,加速了城市的“生态环境危机”.城市绿地能够通过植被的光合作用、吸收作用、隔离阻挡作用、蒸腾以及蒸散作用改善城市的生态环境.目前研究主要集中在降温、增湿、固碳释氧、降噪、抗污染、生物多样性保护等6个方面.关于城区绿地对6种生态环境要素的改善程度、影响范围、机理问题以及不同植被种类生态环境效应的差异情况等,国内外学者都进行了大量详细的研究.基于传统实地观测数据进行城市绿地的生态环境效应研究是目前主要使用的研究方法,部分学者开始使用遥感技术手段研究城区绿地的降温增湿效应.在总结和分析前人研究成果的基础上,从研究内容的不同着手,主要总结并系统评估了目前关于城市绿地6种生态环境效应的研究,为今后相关研究提供参考.

Research progress in the eco-environmental effects of urban green spaces

In the 21^st century, more and more people from rural areas and suburbs pour into cities. Urbanization had become an unstoppable tendency bringing a series of unfavorable consequences. Farmlands in the countries are shrinking. Rural lands, rivers and air conditions are polluted. Because of the rapid development of urban industries and the aggravation of urbanization, large numbers of natural surfaces in the city have been replaced by artificial surfaces. This had resulted in undesirable impacts on urban meteorological and ecological environment, which could have seriously polluted urban ecology and urban environments and accelerated the ecological crisis of urban spaces, and also brought lots of negative effect to the health of human beings. Studies had showed that urban green spaces could absorb carbon dioxide, release oxygen, lower the air temperature, increase air moisture, reduce dust concentration and noise level, while they could protect the biodiversity and reduce air pollution through the photosynthesis, absorption, buffer function, transpiration and evapotranspiration of vegetation. Urban green spaces were one of the best ways to improve the urban ecological environment. Many researchers have done numerous studies about the eco-environmental effects of urban green spaces, mainly in lowering the surface temperature, increasing the air humidity, carbon fixation and oxygen release, noise reduction, pollution filtering and biodiversity protection. The differences of the eco-environment effects of the urban green space were not only reflected on large spatial scales (such as different zones, countries and regions and so on), but also reflected on small spatial scales (such as different underlying surface and vegetation types and so on). What was more, these differences were still not only reflected on large temporal scales (such as different seasons or months), but also on small temporal scales (such as different days, hours and minutes). The main influencing factors of the eco-environment effects of the urban green space were summed up as following: the sun radiation quantity, green space size, the shape of green space (the length and width ratio, height, boundary curvature degree, perimeter area ratio, etc.), the green space landscape structure, the internal composition of green space, vegetation indexes (Normalized difference vegetation index, Leaf area index, Vegetation fraction, Thermal vegetation index, etc), biomass and some other ecological environment factors. Seen from the study methods, most researches about the eco-environment effects of urban green space at home or abroad mainly used two methods. One was based on the observation data. The other was the quantitative remote sensing technique, by which we could retrieve the land surface parameters simultaneously. Currently, most of the researches were based on traditional field observation method. That was because that the quantitative remote sensing technology was limited to a few parameters. In developed countries, the thermal infrared (TIR) remote sensing techniques had been used over urban areas and applied in urban climate and heat environmental studies for more than 30 years, mainly for analyzing land surface temperature (LST) distribution, difference and their relationship with urban development and surface energy fluxes. Recently, the rapidly expanding urban areas of the world aroused an environmental challenge for the 21st century that required both new analytic approaches and new data sources. Thus, remote sensing technology could provide a new study method for researchers in developing countries. With the development of the quantitative remote sensing technology, the remote sensing technology is sure to play a more and more important role in future micro-scale eco-environmental effect studies. Based on differences of existing research methods and contents, the study summarized and systematically evaluated the researches on 6 eco-environmental effects of urban green spaces. The current study difficulties, deficiencies and key directions were indicated for references to future allied researches.