3.1 Environmental conditions
The Whole Tree Chambers that housed our girdled trees tracked ambient environmental conditions. From 6-25 May, cloud cover was minimal, resulting in clear diurnal patterns of PAR with maxima around 1150 µmol m-2 s-1 (Fig. S2). During the experimental period, mean daytime air temperature increased slightly from 17.3 °C (6 to 15 May) before to 18.8 °C (17 to 24 May) after trees were girdled. At the same time, mean daytime VPD rose from 0.7 kPa to 0.8 kPa and mean maximum VPD increased from 1.5 kPa to 2.2 kPa.