Scientists from the University of Melbourne investigated the growth and tolerance of three Eucalyptus species at a mine site in western Victoria, Australia.

SFM1 instruments were installed on 9 trees and data were collected over an 18 month period. Sap velocity data were correlated against temperature and vapour pressure deficit and found one species, Eucalyptus cladocalyx, had greater tolerance to hotter and drier weather than the other two Eucalyptus species. Total tree water use in Eucalyptus cladocalyx ranged from 26 litres per day in summer to 11 litres per day in winter.

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• How can environmental research and monitoring help manage productivity, biodiversity and ecosystem services for a growing population?
• Current concerns with the global carbon cycle
• What are the impact of new crops and land management practices?
• How can we evaluate the costs, benefits and unforseen consequences of new cropping systems?

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• Sap Flow Meter (Heat Ratio Method) - What is the effect of drought on total plant water use over a growing season?
• Sap Flow Meter (Heat Ratio Method) - What is the effect of extreme temperature on daily plant water use?
• Sap Flow Meter (Heat Field Deformation) - Can plants redistribute water from wet roots to dry roots across the stem?
• Stem Psychrometer - What is the effect of drought on stem water potential?
• Logging Band Dendrometer - What is the effect of drought on daily stem shrinkage?
• Infrared Thermometry - Does canopy temperature increase under drought due to less cooling from transpiration?
• Soil Moisture Meter (Standing Wave Principle) - Following a rain event, what is the nature of the wetting front in a 2m soil profile?

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By combining the SFM1 Sap Flow Meter with the PSY1 Stem Psychrometer ICT International has developed an in-situ hydraulic conductivity meter. This technique allows continuous logging of hydraulic conductance over days to weeks at a time as it is non-destructive to the plant stem.

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Aim: To measure sap flow in a rose bush with a narrow diameter stem and to correlate measured data with environmental variables (vapour pressure deficit and solar radiation).

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Aim: Comparing water use strategies of overstory and understory species along an altitudinal gradient in lowland (266m above sea level) and montane (1,011 m above sea level) Atlantic Rain Forest, South-eastern Brazil.

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Project Outline:

• Obtain base line sapflow data for dry sclerophyll Eucalyptus species on an un-irrigated, inland woodlot with a medium
  (approx 670mm ) annual rainfall.
• Compare water use rates of a range of similar Eucalyptus species under the same conditions.

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Measuring Sapflow in the Worlds Tallest Trees

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The aim of the project was to lower the watertable using trees to remediate a salt scald and reclaim pasture land in Bendigo VIC Australia.

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The SFM1 has been widely adopted by researchers in Australia, United States, Germany, Spain, Italy, Brazil, Colombia, Costa Rica and India. Recently, there has been a surge of interest from Japanese researchers and two case studies from Japan are outlined: sap flow in avocado and sap flow in Japanese Cedar.

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Instrumentation for Total Tree Water Use and Behaviour

There is increasing recognition in the forestry industry that water is a vital resource. Not only is water vital for tree growth but increasingly catchment management authorities are required to account for every drop of water in the landscape. Trees transpire a large volume of water however in a multispecies forest certain species transpire more than others. Even in a monoculture plantation tree water use is not uniform and must be accurately measured.

Over the last 20 years there has been increasing evidence showing water movement in trees is complex. It is now recognised that water does not just move from soil to roots, stem, leaves and then atmosphere. Water can move upwards, downwards and laterally depending where there is greatest demand leaving the impression that plants exhibit "behaviour".

This article outlines the mechanism of water movement in plants and why simple principles of physics leads to plant "behaviour". Known as hydraulic redistribution, it is an important aspect of tree water use that must be accounted for in total tree water use. Various case studies of hydraulic redistribution are discussed that highlight the importance of this phenomenon. A number of sap flow methods are available to measure total tree water use however this article emphasises that only two of the many methods available can account for hydraulic redistribution.

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Stem water potential of coffee plants can very easily and accurately be measured using the PSY1 stem psychrometer. The anatomy of the coffee plant is ideally suited to installing the psychrometer and does not exhibit any aggressive wounding around or within the psychrometer chamber. Accurate, reliable and valid data were able to be continuously collected for a period of 45 days in this experiment, measurements could easily have continued for much longer without issue. It is expected that a single installation could remain viable for the duration of the growing season.

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Figure 1

The PSY1 Stem Psychrometer was installed on common garden Squash. This vegetable is widely grown for domestic use in Australia. The xylem water potential was logged every 10 minutes. The initial 4 days of monitoring is shown in Figure 1. Day 1 was cloudy with rainfall. Subsequent days were sunny. The values typically being -1.5 to -1.7MPa on sunny days. The squash are well watered. The squash has a soft stem and further testing in regard to this application is being undertaken.

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Figure 1

The PSY1 Stem Psychrometer was installed on Eucalyptus to measure the xylem water potential. The water potential was logged every 10 minutes. The summer in Australia is October to March. The data is for late October. Winter is April to September and is cool and usually with rainfall. The initial 6 day period shows a water potential of -0.8 MPa on sunny cloud free days (Figure 1, Days 1,2 & 5).

Cloudy days with reduced evaporative demand have lower xylem water potential. Figure 1 shows this as -0.6 MPa (Day 6) and below -0.4 MPa (Day 7) on rainy days. In fact after the rainfall event on Day 6 the night time water potential was 0.0 MPa (Day 6) for the first time.

These trees are well watered having received large amounts of rainfall in the proceeding winter months. Then the water potentials of -0.8 MPa on sunny cloud free days is expected to become more negative as summer progresses, temperatures increase and the soil becomes drier.

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