BOREAS TE-11 Leaf Gas Exchange Measurements Summary The BOREAS TE-11 team collected several data sets in support of its efforts to characterize and interpret information on the sapflow, gas exchange, and lichen photosynthesis of boreal vegetation and meteorological data of the area studied. This data set contains measurements of assimilation and transpiration conducted at the OJP site during the growing seasons of 1993 and 1994. The data are stored in ASCII files. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification BOREAS TE-11 Leaf Gas Exchange Measurements 1.2 Data Set Introduction This data set includes gas exchange measurements of Old Jack Pine (OJP) needles taken during the growing seasons of 1993 and 1994. Assimilation and transpiration measurements were taken continuously from 27-Aug-1993 to 02-Sep- 1993 during 1993 and on 25-Jul-1994 and 26-Jul-1994. 1.3 Objective/Purpose The purpose of the work was to measure the gas exchanges (CO2 and H2O) of an attached branch using a large cuvette operating in a closed system. Both CO2 assimilation and transpiration were monitored together with several microclimatological parameters. The experiment was performed in August-September 1993 and July 1994 at the BOreal-Ecosystem Atmosphere Study (BOREAS) Southern Study Area (SSA) OJP site. 1.4 Summary of Parameters In the data file, assimilation and transpiration data are expressed per unit leaf area. Air temperature, relative humidity, and photosynthetically active radiation (PAR) are also measured in the cuvette. Time step is 30 minutes. 1.5 Discussion These data were extrapolated using leaf area index measurements performed by other teams on the same site, and a comparison was performed using a micromet estimate of the whole-stand transpiration/assimilation. The water-use efficiency (assimilation/transpiration) at the branch level was computed and then multiplied by the transpiration of the trees (derived from sapflow measurements) to obtain the net assimilation at the tree level. 1.6 Related Data Sets BOREAS RSS-04 1994 Southern Study Area Jack Pine LAI and fPAR Data BOREAS RSS-07 LAI, Gap Fraction, and fPAR Data BOREAS TE-04 Gas Exchange Data from Boreal Tree Species BOREAS TE-05 Leaf Gas Exchange Data BOREAS TE-10 Leaf Gas Exchange Data BOREAS TE-11 Sapflow Data BOREAS TE-12 Leaf Gas Exchange Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Bernard Saugier, Professor Jean-Yves Pontailler, Technical Manager 2.2 Title of Investigation Seasonal Variations of Net Photosynthesis and Transpiration at the Branch Level 2.3 Contact Information Contact 1 B. Saugier Ecologie vegetale, bat. 362 Universite Paris-Sud Orsay cedex France 33.1.69.41.71.36 33.1.69.41.72.38 (fax) saugier@psisun.u-psud.fr Contact 2 J.Y. Pontailler Ecologie vegetale, bat. 362 Universite Paris-Sud Orsay cedex France 33.1.69 41 71 37 33.1.69.41.72.38 (fax) ecoveg@psisun.u-psud.fr Contact 3 Andrea Papagno Raytheon STX Corporation NASA GSFC Greenbelt, MD (301) 286-3134 (301) 286-0239 (fax) apapagno@pop900.gsfc.nasa.gov Contact 4 Shelaine Curd Raytheon STX Corporation NASA GSFC Greenbelt, MD (301) 286-2447 (301) 286-0239 (fax) shelaine.curd@gsfc.nasa.gov 3. Theory of Measurements A whole branch was enclosed in a large cuvette located in the top of the canopy. Between measurements, a fan blew air from the outside through the chamber at a high flow rate (0.045 m3/s) to prevent overheating. Every 30 minutes, the cuvette was closed for 5 minutes in order to allow a measurement of both CO2 assimilation and transpiration using the closed system method. CO2 concentration was measured using an Infrared Gas Analyzer (IRGA) system, and air humidity was measured by a capacitive sensor. Gas exchange was computed as: A = (V/Sf) * (Dc/Dt) * (1/p) E = (V/Sf) * (De/Dt) * (1/p) Where V is the cuvette volume (moles of air); Sf is the leaf area (m2); c and e are the CO2 and H2O partial pressures (µb or mb), respectively, Dx/Dt is the derivative of x with respect to time t (sec), and p is the atmospheric pressure (mb or hPa). Thus, A is in the units of µmol/m2s, and E is in mmol/m2s. 4. Equipment 4.1 Sensor/Instrument Description The big cuvette is referred to as a branch bag, which is a 0.25 m3 transparent chamber made of an acrylic frame covered with a 75 µm thick polypropylene film. A turbine, located on the scaffolding, injected air at a high flow rate into the bag through a flexible pipe (45 dm3 per second). At the bag level, the air inlet and outlet were fitted with thin, light perspex shutters: the air flow opened it up, and it closed hermetically when the flow stopped. When a gas exchange measurement was required, a relay, activated by a Campbell 21X data logger, shifted the main power supply from the turbine to a couple of fans located in the bag. This caused the branch bag shutters to close immediately. The decrease in CO2 and H2O concentration inside the bag was then monitored for 5 minutes. A CID CI-301 gas analyzer was used to monitor CO2 and a Vaisala capacitive probe model HMB30YB measured air temperature and humidity. PAR was measured inside the bag using a laboratory-made, cosine-corrected, blue-enhanced gallium arsenide sensor. 4.1.1 Collection Environment Gas exchange measurements took place at the SSA-OJP site. 4.1.2 Source/Platform None given. 4.1.3 Source/Platform Mission Objectives None given. 4.1.4 Key Variables Assimilation and transpiration. 4.1.5 Principles of Operation None given. 4.1.6 Sensor/Instrument Measurement Geometry None given. 4.1.7 Manufacturer of Sensor/Instrument HMB30YB Capacitive Probe: Vaisala Oyj. Helsinki, Finland www.vaisala.com LI-190SB PAR Sensor: LI-COR, Inc. Box 4425 Lincoln, NE 68504 (402) 467-3576 CI-301PS Portable Photosynthesis System: CID, Inc. 4018 NE 112th Avenue Suite D-8 Vancouver, WA 98682 1 (800) 767-0119 (360) 254-7923 (fax) www.cid-inc.com 4.2 Calibration The IRGA was calibrated using cylinders. The Vaisala probe was calibrated using a laboratory-made air supply system offering an accurate dewpoint regulation (using a condenser). The PAR sensor was calibrated in daylight conditions against two new Li-Cor sensors model LI-190 SB. 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration None given. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods A Campbell 21X data logger, with 4 input channels and one relay output per bag was used to collect the data. One bag was used in 1993 for 1 week, and two were used for 1 month in 1994. 6. Observations None given. 6.1 Data Notes None given. 6.2 Field Notes The team came from France with a branch bag made of unassembled parts. It took 2 days to assemble it and install it on the top of the canopy access tower. The team had hoped for a good clear day, but the best days had periods of sunshine and scattered clouds. Data seemed of good quality; transpiration rates were lower than expected, with maximum values of 0.8 mmol H2O/m2s, leading to estimates of the canopy transpiration close to those obtained using the sapflow method. At night, the system was able to measure low respiration rates. At the end of the experiment, the branch was harvested in order to measure leaf area (HASL) using the displacement method suggested for conifer shoots in the BOREAS Experiment Plan (Sellers and Hall, 1994, Appendix k). 7. Data Description 7.1 Spatial Characteristics A dominant branch was chosen. In 1994, the two branches were close to each other, but located on different trees. 7.1.1 Spatial Coverage The measurement site and its associated North American Datum of 1983 (NAD83) coordinates are: OJP, site id G2L3T, Lat/Long: 53.91634 N, 104.69203 W, Universal Transverse Mercator (UTM) Zone 13, N: 5974257.5 E: 520227.7 7.1.2 Spatial Coverage Map None available. 7.1.3 Spatial Resolution None given. 7.1.4 Projection None given. 7.1.5 Grid Description None given. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage The data were collected at varying periods from 27-Aug-1993 to 10-Aug-1994. 7.2.2 Temporal Coverage Map None given. 7.2.3 Temporal Resolution Measurements were taken every 30 minutes, for about 6 days in 1993 (27-Aug-1993 to 02-Sep-1993, night and day) and from 25-Jul-1994to 10-Aug-1994. For various reasons (distance between chamber and IRGA, stomatal response, etc.), assimilation and transpiration were not computed according to the same durations: CO2 assimilation was computed on a 4-minute basis, while transpiration calculations used the first 1.5 minutes of every experiment. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (te11lgxd.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (te11lgxd.def). 8. Data Organization 8.1 Data Granularity All of the Leaf Gas Exchange Measurements Data are contained in one dataset. 8.2 Data Format(s) The data files contain numerical and character fields of varying length separated by commas. The character fields are enclosed with a single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition file (te11lgxd.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms All signals, Volts (IRGA and Vaisala), or millivolts (PAR), were treated and stored by the data logger. CO2 assimilation was computed according to the formula: A = ((CO2i-CO2f)/sec)*(Vol/Sf)*(0.044642*(273/(273+Ta))) with: CO2i: Initial CO2 concentration (vpm) CO2f: Final CO2 concentration (vpm) sec: Time interval (s) Vol: Volume of the system (dm3) Sf: Leaf area (HASF, m2) Ta: Air temperature (°C) Transpiration was computed according to the formula: E = (Vol/Sf)*((Xf-Xi)/sec)*0.05555 with: Xi: Initial water content (g/m3) Xf: Final water content (g/m3) Time interval "Sec" is equal to 90 seconds for the transpiration estimation and to 250 seconds for CO2 assimilation. This resulted from a careful examination of the plots of CO2 and absolute humidity versus time and selection of linear sections of both plots. Thus, seconds 0 to 90 were used for humidity and seconds 30 to 280 were used for CO2. 9.2 Data Processing Sequence 9.2.1 Processing Steps See Sections 3 and 4.1. 9.2.2 Processing Changes None given. 9.3 Calculations See Section 9.1.1. 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables Transpiration and assimilation. 9.4 Graphs and Plots None given. 10. Errors 10.1 Sources of Error The accuracy of the gas analyzer in absolute mode and the eventuality of leaks, especially during windy periods, are probably two limiting factors. 10.2 Quality Assessment The system appeared able to measure very low respiration rates at night. 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgment None given. 10.2.3 Measurement Error for Parameters None given. 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center Data were examined for general consistency and clarity. 11. Notes None given. 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data There are some missing data: Day 240, 14:00 to 18:30 (power failure) Day 245, 02:00 to end (IRGA malfunction) 11.3 Usage Guidance None given. 11.4 Other Relevant Information None given. 12. Application of the Data Set This data set can be used to examine the gas exchange of OJP in the boreal forest. 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description None given. 14.2 Software Access None given. 15. Data Access 15.1 Contact Information Ms. Beth Nelson BOREAS Data Manager NASA GSFC Greenbelt, MD (301) 286-4005 (301) 286-0239 (fax) Elizabeth.Nelson@gsfc.nasa.gov 15.2 Data Center Identification See Section 15.1. 15.3 Procedures for Obtaining Data Users may place requests by telephone, electronic mail, or fax. 15.4 Data Center Status/Plans The Terrestrial Ecology (TE)-11 gas exchange data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The BOREAS contact at ORNL is: ORNL DAAC User Services Oak Ridge National Laboratory (865) 241-3952 ornldaac@ornl.gov ornl@eos.nasa.gov 16. Output Products and Availability 16.1 Tape Products None. 16.2 Film Products None. 16.3 Other Products Tabular American Standard Code for Information Interchange (ASCII) files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None given. 17.2 Journal Articles and Study Reports Dufrene E, J.Y. Pontailler, and B. Saugier. 1993. A branch bag technique for simultaneous CO2 enrichment and assimilation measurement on beech (Fagus sylvatica). Plant, Cell and Environment 16, 1131-1138. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 94). Sellers, P., F. Hall, H. Margolis, B. Kelly, D. Baldocchi, G. den Hartog, J. Cihlar, M.G. Ryan, B. Goodison, P. Crill, K.J. Ranson, D. Lettenmaier, and D.E. Wickland. 1995. The Boreal Ecosystem-Atmosphere Study (BOREAS): An Overview and Early Results from the 1994 Field Year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Sellers, P., F. Hall, and K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPSDOC 94). Sellers, P. and F. Hall. 1996. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1996-2.0, NASA BOREAS Report (EXPLAN 96). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPSDOC 96). Sellers, P J., F.G. Hall, R.D. Kelly, A. Black, D. Baldocchi, J. Berry, M. Ryan, K.J. Ranson, P.M. Crill, D.P. Lettenmaier, H. Margolis, J. Cihlar, J. Newcomer, D. Fitzjarrald, P.G. Jarvis, S.T. Gower, D. Halliwell, D. Williams, B. Goodison, D.E. Wickland, and F.E. Guertin. 1997. BOREAS in 1997: Experiment Overview, Scientific Resultsand Future Directions. Journal of Geophysical Research 102 (D24): 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms A - Assimilation ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System DAAC - Distributed Active Archive Center E - Transpiration EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center HASL - Leaf Area IRGA - Infrared Gas Analyzer NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration NSA - Northern Study Area OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park PAR - Photosynthetically Active Radiation SSA - Southern Study Area TE - Terrestrial Ecology URL - Uniform Resource Locator UTM - Universal Transverse Mercator 20. Document Information 20.1 Document Revision Date Date written: 01-Mar-1994 Last updated: 14-Sep-1998 20.2 Document Review Date(s) BORIS Review: 24-Nov-1997 Science Review: 20.3 Document ID 20.4 Citation B. Saugier Universite Paris-Sud, FRANCE 20.5 Document Curator 20.6 Document URL Keywords Assimilation Transpiration TE11_Leaf_Gas_Exchange.doc 09/14/98