|  |

| |

Enabling better global research outcomes in soil, plant & environmental monitoring.

Smart Trees, Smart Kids

SMART Trees, SMART Kids – Empowering a generation through the science of Sap Flow


The SMART Tree project is a collaboration of diverse interest groups and stake holders to form a unique pilot program being trialled by the NSW Department of Education in Australia. It is designed to engage school students in science and inspire them through practical experiments, focussing on sap flow measurements and their contribution in the fundamentals of plant science.

Experiments are simple, teaching experimental protocol and scientific rigour, identifying variables, basic development and testing of hypothesis, result analysis and drawing conclusions. Initial sites were established in the grounds of three schools to compare the water use of different species within the same ecosystem.

All schools are using the same sap flow principle (Heat Ratio Method) making the results immediately compatible and comparable. The theory of hydraulic redistribution cannot only be taught, but the principles observed by students and compared across schools and across countries. The sap flow data is being incorporated into many traditional disciplines such as, biology, maths, physics, and agriculture as well as establishing synergies with less traditional disciplines for a science centric focus. Economics students will use the data for pricing carbon, incorporating the impact tree water use has on carbon sequestration models to improve carbon accounting techniques. Computer science students are writing software to integrate sap flow into their daily lives.

Thanks to the Australian National Broadband Network providing high speed internet access, students can share their research across the country or the globe. A number of internationally renowned Sap Flow researchers have signed on to be involved as guest lecturers. Prof. Cermak & Nadezdina from Mendel University (Czech Republic) will attend the end of year project symposium as keynote speakers and will chair the student symposium in Armidale, Australia, where research results will be presented by the students.

Materials & Methods:

Three sites were initially established in the regional town of Armidale, NSW, Australia (latitude 30.5°S longitude 151.6°E) and the suburb of Croydon, Sydney, NSW, Australia (latitude 33.8°S longitude 151.2°E). Climate between sites varies based on the mean average temperatures (Armidale 19.3 to 7.4°C and Sydney 21.7 to 13.8°C) and annual rainfall (Armidale 1,060 mm and Sydney 1,214 mm) with Armidale being a colder slightly drier climate due to its elevation of 980m compared to Sydney’s coastal elevation of 39m ASL, but in general both are broadly classified as Temperate climates.

The sap flow principle employed is the Heat Ratio Method (HRM) which is a modified heat pulse technique. The technique is invasive requiring that two measurement probes be inserted into the sapwood of the tree, equidistance above and below a central heater. A pulse of heat is used to track the movement of water in the conducting xylem of the plant. The ratio of the resultant temperature increase is used to determine, initially the raw heat pulse velocity, and subsequently the sap velocity, and ultimately volumetric sap flow as described in Burgess et. al 20011.

Three species, Eucalyptus viminalis (Ribbon Gum), Angophora costata (Sydney Red Gum), and Eucalyptus stellulata (Black Sally) were installed with SFM1 Sap Flow Meters at three schools, PLC & TAS Armidale and PLC Croydon (Sydney). The sap flow was continuously monitored from the beginning of Summer (December 2012).

Figure 1. Comparison of Sap Flow rates for three Eucalyptus species at three different school campuses.

Students have begun analysing basic plant environment responses, comparing their data to the data from the other schools via online data access through a central data repository.

Students have already recorded a significant physiological response to ambient environment interactions as highlighted in Figure 1. It would appear that as a result of a wide spread rain event (not shown) sap flow has been suppressed through a reduction in evaporative demand affecting all three trees across two physically distant regions (Sydney & Armidale).

This resulted in two of the three species, E. viminalis & A. costata, experiencing reverse flow and the third species, E. stelullata, experiencing an extended period of zero flow.

Figure 2. Comparison of Cumulative Sap Flow rates for three Eucalyptus species at three different school campuses over 146 days.

Species Stem Diameter
Sap Wood Thickness
Avg. Daily Use
Cumulative Use
PLC Armidale E. viminalis 35.3 4.5 49.35 L/day 7305
(148 days)
PLC Croydon A. costata 98.0 2 37.87 L/day 5530
(146 days)
TAS Armidale E. stellulata 8.4 3.5 6.58 L/day) 962
(146 days)

Table 1. Summary of average daily water use rates and cumulative water use for three eucalyptus species on three different school campuses.

A sap flow database is being constructed including previously undocumented species that is building the knowledge of the local Landcare and tree groups, and will be used as a resource by the University of New England both for teaching and research.


Although, an Australian pilot program, schools from Czech Republic, Japan, Jordan, and the USA have already expressed interest in joining. One school student from Czech Republic has already registered to present at the end of year symposium to be held in Armidale in October 2013.

The involvement from the Armidale Tree group has yielded mutual benefits for both the tree group and the students. Expertise on the local native flora has been transferred to the students from the Armidale Tree Group. Further synergies are being built with the Armidale chamber of commerce and local businesses working towards the establishment of a local carbon trading scheme.

The catalyst for the carbon trading scheme was the potential to use sap flow and dendrometer data to build a better carbon sequestration model that more accurately accounts for the carbon sequestered in the local community, and therefore more accurately accounts for carbon permits traded.


The science of sap flow has already successfully invigorated the school curriculum with children across Australia and the world looking at trees and plants differently, questioning how does the plant work. However, the final milestone of success will be if the program is formally included in the education curriculum, both in NSW and schools internationally. This will result in a greater focus on science and improved learning outcomes for students around the world.


1. Stephen S. O. Burgess, Mark A. Adams, Neil C. Turner, Craig R. Beverley, Chin K. Ong, Ahmed A. H. Khan and Tim Bleby 2001 An improved heat pulse method to measure low and reverse rates of sap flow in woody plants Tree Physiology 21, 589-598.