Delta Electronics SS1-UM-1.05 user manual Measurement options, Experiment design

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Measurement options

Experiment design

This section discusses the factors that bear on the experimental objectives you wish to achieve. It should help you answer questions like:

•What equipment do I need?

•What readings must be taken?

•Will I have to wait for particular times of day or weather conditions?

The type of study you propose to do will determine the time of year and duration of the experiment, and whether you are interested, for example, in monitoring growth by interception of solar radiation, or perhaps in the canopy structure as well.

Some canopies types (the non-uniform ones) preclude the use of the SunScan’s direct LAI readout. You could, however, characterise the 3-dimensional light distribution within your canopy at different heights, or along transects through it. For brevity we will call this approach “PAR mapping” in the discussion below

Answers to the above questions are complicated, but the following tables should give you a good appreciation of the main issues involved.

Above-canopy reference requirements

This refers to measurements of PAR incident on the canopy, made at the same time as the below-canopy measurements. The question is whether to use a BFS.

Beam Fraction sensor

A BFS connected to the SunScan probe provides the best option, because you can operate with fewest restrictions. However, with some canopy types this may not be practical.

The next best option is to use the SunScan probe (without the BFS) sequentially above and below the canopy, but you may be restricted to times when the light levels are not changing fast.

Independent PAR sensor

If that method is not practical either, you may have to rely on independent records of incident PAR from a separate sensor. In addition to slowly changing light levels, you may also have to average measurements in each place over periods of a few minutes, furthermore the direct LAI readout is not available. This is the least convenient situation, and it will not always be considered in the analysis below.

You cannot currently use the SunData software to merge independent records of transmitted PAR and incident PAR to get LAI.

Direct and Diffuse components

Assuming that you make your above-canopy measurements on the SunScan (with or without a BFS), then the next table summarises whether you need to measure the Direct and Diffuse components of the incident light. If you do not need the separate components, you benefit because the BFS is quicker to set up (there is no need to re- adjust its shade ring, once it has been set up correctly).

Type of study

Incident PAR

Incident PAR

 

Total only

Direct & Diffuse components

Fractional interception

Yes

No

LAI

No

Yes

PAR mapping

Yes

Possibly

SunScan User Manual v 1.05

Measurement options • 41

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Contents SS1-UM-1.05 SunScanAcknowledgements CopyrightTrademarks CE conformityContents Measurement options Menus and Screens More Psion and file handling notesLAI theory Technical Reference sectionIndex AppendicesIntroduction How to use the manualsSunScan Canopy Analysis System Organisation of this manualSunScan probe Field accessoriesBeam Fraction sensor Data Collection TerminalWorkabout and SunScan probe Getting StartedPreliminary checks Checking the Workabout hardware Installing the s/w Installing the SunData s/w in your PCSunData s/w Diskette What the s/w doesRunning SunData Setting up your PCs COM portWorkabout to PC Communication checksSunScan probe to PC Running SunData in Windows Working with the Workabout SunScan TutorialAbout this tutorial Starting SunData in the Workabout What to do if you get lostStarting the PC software Using a PC instead of the WorkaboutThis page is intentionally blank Working through the menu options Setting up a measurement sessionHot Keys File SavingTaking readings Using the Emulator modeWithout a Beam Fraction Sensor Connecting the SunScan probeConnecting the Beam Fraction Sensor Measuring Leaf Area Index without a Beam Fraction Sensor Averages Reviewing your data fileTo the PC Transferring the data file to your PCFrom the Workabout Initiating the file transfer from the Workabout Meanwhile, on the PC Conclusion of the Tutorial RS232 communication problemsSunData Screens on the Workabout File SettingsMenus and Screens Utils ContdQuit Navigating Psion directories and screens More Psion and file handling notesWorkabout User Guide Navigating the Psion directories and screensPsion subdirectory usage in file select dialogs Flashcards reformatting Re-installing the SunData application iconDeleting unwanted Workabout files Data memory management Configuration and data file handlingSunData Configuration files Creating a configuration file Default .cfgRestoring a configuration Data files .CSV file Displaying data files on your PC .PRN file Data file layouts and data groups Page Above-canopy reference requirements Measurement optionsExperiment design Canopy type and LAI estimates Canopy Sampling volumeCanopy type and BFS practicalities Planning for the sun’s position Preferred light and weather conditionsAbsorption Advice on Absorption and Eladp valuesSetting Eladp Estimating Eladp in the field Relationship between Mean Leaf Angle and EladpLAI, PAR and All displays Workabout setupSunScan System Measurement modes Autolog function Probe handling in the field Measurement procedures in the fieldProbe GO button Levelling the probeBFS handling in the field Using the tripodUse of the tripod WorkaboutExtension cables, and the location of the BFS Finding North, and setting the shade ringLevelling the BFS Factory light calibration PAR calibrationsChecking the probe/BFS matching Recalibrate optionRestoring the factory calibration Routine maintenance and cleaningEffect of the shade ring on the BFS Comparing the calibration with other PAR sensorsSunScan probe and Beam Fraction Sensor Environmental and moisture protectionIngredients of the LAI computation method LAI theoryTheory versus reality Derivation of Wood’s SunScan canopy analysis equationsMajor assumptions Transmission of Diffuse Light Beers law for canopy absorptionCampbells Ellipsoidal LAD equations Transmission fraction τ Is given by I/I0 Diffuse light transmission cosine corrected sensor Modelling the canopy transmissionDetail Accuracy of LAI calculations Functions used to model canopy transmissionDiffuse light cosine response sensor Diffuse light hemispherical response sensorExp 0.1 . x . atan 0.9 Atan L Q Spher Modelling incomplete PAR absorption and scatteringSummary Scientific referencesCalculating zenith angles Jones, Hamlyn G Plants and Microclimate second edition. CUP Technical Reference section Maintenance and repairChecking the batteries SunScan probe batteriesChecking the desiccant Factory calibration method Re-setting the factory calibrationChecking the PAR calibration Problems running the SunData application TroubleshootingPsion Workabout While running SunDataInsufficient power to write data reported Technical Support SunScan Probe Type SS1 SpecificationsBeam Fraction Sensor type BF1 Data Collection Terminal type DCT1 Psion WorkaboutTelescopic Tripod type BFT1 Carrying Case type SCC1Spares Kit type SPS1 Logging CablesSpectral response PAR PerformanceSunScan system cosine response Cosine responses of probe and BFSLogging the probe as a Linear Quantum Sensor AppendicesLogging the Beam Fraction sensor SunData PC s/w Upgrading the SunScan systemWorkabout SunData s/w Revision HistoryChoice of different programs File transfer between Workabout and PCPsiWin Workabout Remote LinkSlink and Rcom Example using SlinkDrives on the PC are referred to as REMA, Remc REM = remote Documentation of Rcom and Slink Example using RcomAlternative file transfer mechanisms Using the Workabout Comms applicationSending a file to a Communication program Sending a file to a serial printerGlossary Page Accuracy IndexIndex Field use 39, 46, 48, 50, 51, 58
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