2.1 Environmental monitoring
A weather station was used to record ambient conditions at the Whole Tree Chamber site. The station recorded air Tair, relative humidity (RH, %) (HMP45C, Vaisala, Helsinki, Finland) and photosynthetically active radiation (PAR, µmol m-2s-1) (SQ-110, Apogee Instruments Inc., Logan, Utah, USA), which were all stored on a data logger at 1-minute intervals (Logger: CR3000, Campbell Scientific, Garbutt, Australia). We used the formula from Snyder & Shaw (1984) to calculate vapour pressure deficit (VPD, kPa) from measurements of Tair and rH. During the experiment, the climate control system of each chamber tracked ambient conditions based on measurements collected by the weather station.