Abstract: Urban green space ecosystems could regulate thermal environmental problems, and play a crucial role in mitigating urban heat island (UHI) effects. We analyzed the relationships between the leaf area index (LAI), vegetation coverage (VC), gross primary productivity (GPP) of urban green spaces and the land surface temperature (LST) in Guangzhou, and explored how UHI mitigation function would be affected by the urban ecosystem quality. The results showed that there were strong negative correlations between LAI, VC, GPP and LST, with Pearson correlation coefficients being -0.73, -0.886, and -0.892, respectively. The correlation coefficient between ecosystem quality index (EQI) and LST was -0.831, suggesting that the quality improvement of urban green spaces would alleviate UHI. Both LST and EQI of Guangzhou exhibited pronounced spatial heterogeneity. Liwan, Haizhu, and Yuexiu districts were not only the industrial agglomeration belts but also the core areas of UHI in Guangzhou. Their ecosystem quality was relatively poor (with EQI values rating good or below). In contrast, ecosystem quality of Zengcheng and Conghua districts was relatively good, with the EQI of both districts being at “good” level or above. Therefore, the UHI effects of those districts were relatively weak. When the regional EQI was low, green space ecosystems were difficult to reduce the LST through a large amount of transpiration, evaporation and photosynthesis, showing weak regulatory functions of the UHI effect. The cooling effect of green spaces would be quite noticeable only if the ecosystem quality of green spaces attained a specific standard. When the regional EQI exceeded 55, the cooling effect was relatively obvious. Moreover, when the EQI was greater than 75, the cooling effect was the most remarkable. In the future planning and construction of urban green space ecosystems, efforts should focus on expanding the area of urban green spaces and enhancing the ecosystem quality, which would help strengthen the regulatory function of urban green space ecosystems in dealing with UHI effect.

Key words: