Canopy transpiration and its cooling effect of three urban tree species in a subtropical city- Guangzhou, China

Abstract

Quantitative evaluation of canopy transpiration and its cooling effect can contribute to the selection of suitable tree species to alleviate heat island effect in urban area. To achieve this aim, we investigated the canopy transpiration and its cooling effect of three common urban tree species (Schima superba, Eucalyptus citriodora and Acacia auriculaeformis) in a subtropical city (Guangzhou) based on continuous sap flow measurement as well as environmental factors monitoring. The interspecific differences in biological attributes that impact tree transpiration and then the cooling effects were further studied. Results indicated that the strongest canopy transpiration and its cooling effect of three species were observed in the summer along with favorable environmental factors (higher soil water content (SWC)11SWC: Soil water content; PAR: photosynthetically active radiation; VPD: vapour pressure deficit; EL: canopy transpiration and photosynthetically active radiation (PAR)). Furthermore, significant interspecific differences in cooling effect of transpiration were found in our study, S. superba has the highest canopy transpiration cooling effect among three species due to its favorable bio- and hydraulic characteristics. These findings will help to promote the ecological benefits of urban forests by efficient management practices to a certain extent.