Transpiration Of Five Typical Tree Species Under An Urban Environment In The Semi-arid Region

The selection of tree species that consuming less water is one of the key aspects for the urban forestry practices and water management. Using thermal dissipation probes (TDP) method, the sap flow of Pinus tabulaeformis Carr., Pinus bungeana Zucc., Populus bolleana Lauche., Robinia pseudoacacia L., Larix principis-rupprechtii Mayr. was monitored at the Hohhot Arboretum, and the environmental factors were measured by using small automatic weather station and soil moisture sensor simultaneously, as well as to analyze the relationships between transpiration and environmental factors.The results showed that:(1)The diurnal changes of sap flow density among different tree species showed a similar trend on sunny and cloudy day. All species showed single peak curve excepted Robinia pseudoacacia L. that showed a bimodal curve.(2) Comparing the sap flow density of different tree species showed that, small DBH rank:Pinus tabulaeformis Carr.D>Larix principis-rupprechtii Mayr.> Populus bolleana Lauche.> Pinus bungeana Zucc.> Robinia pseudoacacia L.; middle DBH rank:Populus bolleana Lauche.>Pinus tabulaeformis Carr.> Pinus bungeana Zucc.>Larix principis-rupprechtii Mayr.>Robinia pseudoacacia L.; large DBH rank:Populus bolleana Lauche.>Pinus tabulaeformis Carr.>Pinus bungeana Zucc.> Larix principis-rupprechtii Mayr.>Robinia pseudoacacia L.. During experimental period, the sum water consumption of Pinus tabulaeformis Carr. and Populus bolleana Lauche. reached4385.0±2815.3、8495.3±6139.4kg, respectively., which far higher than other tree species. High sap flow density and sap wood area led to high water consumption.(3) Correlation analysis showed that solar radiation, vapor pressure deficit was the main factors that influenced tree transpiration. The multiple linear regression based on environmental factors could explain64.1%of Pinus tabulaeformis Carr.’s sap flow density, as well as63.5%of Pinus bungeana Zucc.,79.1%of Populus bolleana Lauche.,59.5%of Robinia pseudoacacia L.,76.9%of Larix principis-rupprechtii Mayr.(4)The percentage of nighttime sap flow density that occupied the total day was10.9%,6%,14.1%,13.1%,12.9%respectively.