PLC Sydney, PLC Armidale and The Armidale School have taken part in a science pilot
program called the SMART Tree Project. The schools each have a solar powered SAP flow
meter on a tree in their school. These meters measure plant water use, (sap flow). This data
can then be analysed with reference to data obtained on temperature, sunlight, humidity
and wind direction. PLC Sydney has the sap flow meter on a lemon scented gum (Corymbia
citriodara). PLC Armidale has 2 trees with sap flow meters, a Ribbon Gum Tree (Eucalyptus
viminalis) and the introduced, deciduous Poplar (Populus trichocarpa)The Armidale School
monitors Eucalyptus stellulata.
The schools collaborate by sharing data from each of the meters on the trees. Over twelve
months of data have been collected. The sap flow meters use the heat ratio method (HRM)
of measuring the sap flow in xylem tissue. This uses a short pulse of heat as a tracer. By
measuring the rate of heat transferred to two symmetrically placed temperature sensors the
magnitude and direction of water flow can be detected.
PLC Sydney also has an automated weather station which measures wind speed, wind
direction, air temperature, humidity and atmospheric pressure. Last year during a week of
prolonged bushfires, the students analysed the data to determine whether higher pollution,
wind speed and temperature had caused a decrease in sap flow; the sap flow in fact
increased.
PLC Armidale has compared the sap flow in Summer and Winter of the deciduous and
native trees. They have noted a significant decrease in sap flow after an extended drought
period. In addition they have noted that the trees reduce sap flow prior to an extreme
temperature day reduced.
This research could provide data when considering issues such as climate change, drought
policy and natural science management. Presbyterian Ladies’ College Sydney would like to
present their findings at the 10th International Student Science Conference.
