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.