2.2 Trees and phloem girdle
One Eucalyptus tereticornis tree was grown at ambient
Tair in each of the 6 chambers for 17 months (December
2012 – May 2014). Trees grew in 25 L pots for three months before
transplanting the seedlings into the chamber soil (see Drake et al.
2016). On the day of girdling (16 May 2014), trees were 8.0 to 9.3 m
tall and basal stem diameter ranged from 78 to 103 mm (Table 1). Trees
were phloem girdled by removing a 5 cm wide collar of bark (6-8 mm
thick) from the stem at 600-700 mm above the soil surface (see Fig. S1).
Dehydration of the exposed sapwood was minimised by wrapping wet paper
towels (kept moist daily) and plastic foil around the injured stem.
Girdled trees remained well-watered in the WTCs until 26 May 2014, when
they were destructively harvested.
Prior to girdling, total leaf number of each tree crown was determined
by manual counting (see Drake et al . 2016). At the end of the
experiment, we collected a subset of 300 leaves from each tree crown to
estimate the average area of leaves (Li3600C Area Meter, Li-COR,
Lincoln, USA). Multiplying this value with the total number of leaves
produced a good estimate for total leaf area of each tree, which was
used to express H2O and CO2 fluxes on a
leaf area basis using a ‘big leaf’ type approach (e.g., McNaughton &
Jarvis 1991).