Variations in Sap Flux Density of Three Urban Tree Species and Their Main Environmental Influencing Factors in Different Timescales in the Beijing Metropolitan Area

Despite the importance of landscape design and water-resources management for urban planning, urban-forest transpiration was seldom estimated in situ. Detailed data on different trees’ water resource use effect climatic fluctuations their behaviour timescales are limited. In this study, we used a thermal dissipation method to measure sap flux density (Js) three tree species (Pinus tabulaeformis Carrière, Cedrus deodara (Roxb.) G. Don, Robinia pseudoacacia Linn.) from 1 May 2008 30 April 2016 Beijing Teaching Botanical Garden. The effects environmental factors were also analyzed. results showed that there significant differences trees daily, seasonal, interannual timescales. hourly, mean Pinus higher than pseudoacacia. seasonal Js tabulaeformis, deodara, summer 18.67, 16.19, 41.62 times winter over 2008–2015. annual 1.25–1.72 1.26–1.82 responses varied differently daily pattern day-to-day variation corresponded closely air temperature (Ta), soil (Ts), solar radiation (Rs), vapor pressure deficit (VPD). Jarvis–Stewart model based Ta, Rs, VPD more suitable simulation main factor affecting Ta However, Ts. variations mainly influenced by wind speed (w) content (SWC), respectively. selected could not explain an timescale. findings present study provide theoretical support predicting consumption plant under background climate change future.