Articles
SAP FLOW MEASUREMENTS IN FRUIT TREES – ADVANTAGES AND SHORTFALLS OF CURRENTLY USED SYSTEMS
Article number
449_38
Pages
267 – 272
Language
Abstract
A variety of methods is available to calculate mass flow of water in the transpiration stream by using heat energy as a tracer.
Methods like the heat balance, heat pulse, Granier or Cermak systems offer the possibility of measuring the transpiration stream of whole trees or single branches in the natural environment with little or no disturbance of the plant.
Whereas heat pulse, Granier or Cermak systems are stem-segment methods, i.e. calculate either flow speed or mass flow in a particular part of the stem, the heat balance method measures overall mass flow in the trunk.
The latter method, however, is limited to smaller stem sizes up to 8 – 10 cm in diameter.
The different systems are reviewed in terms of their applications to stem size, commercial availability and/ or ease of installation and construction as well as their short (few minutes) or long (24 hours or more) term accuracy.
These factors determine their usefulness for the different applications ranging from simple base data collection for irrigation purposes up to complex, dynamic studies.
It is shown, that especially the latter application requires careful construction of probes and cannot be served by currently available commercial instruments.
Methods like the heat balance, heat pulse, Granier or Cermak systems offer the possibility of measuring the transpiration stream of whole trees or single branches in the natural environment with little or no disturbance of the plant.
Whereas heat pulse, Granier or Cermak systems are stem-segment methods, i.e. calculate either flow speed or mass flow in a particular part of the stem, the heat balance method measures overall mass flow in the trunk.
The latter method, however, is limited to smaller stem sizes up to 8 – 10 cm in diameter.
The different systems are reviewed in terms of their applications to stem size, commercial availability and/ or ease of installation and construction as well as their short (few minutes) or long (24 hours or more) term accuracy.
These factors determine their usefulness for the different applications ranging from simple base data collection for irrigation purposes up to complex, dynamic studies.
It is shown, that especially the latter application requires careful construction of probes and cannot be served by currently available commercial instruments.
Authors
P. Braun
Keywords
Heat balance, heat pulse, Granier system, Cermak system, irrigation scheduling, modelling, water relations
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