BOREAS TE-12 Leaf Gas Exchange Data Summary The BOREAS TE-12 team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, and gas exchange of boreal vegetation. This data set contains measurements of leaf gas exchange conducted in the SSA during the growing seasons of 1994 and 1995 using a portable gas exchange system. The data are stored in tabular 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 This data set includes single leaf gas exchange measurements conducted in the boreal forest during the growing seasons of 1994 and 1995. 1.1 Data Set Identification BOREAS TE-12 Leaf Gas Exchange Data 1.2 Data Set Introduction Field studies of single leaf gas exchange properties of dominant vascular plant species were conducted at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) in 1994 and 1995 using a portable gas exchange system. 1.3 Objectives/Purpose The purposes of the work were to: 1) Quantify the response of leaf gas exchange properties (e.g., net CO2 assimilation rate and stomatal conductance) to environmental conditions in the field. 2) Determine diurnal and seasonal changes in leaf gas exchange properties. 1.4 Summary of Parameters Each data record includes the date and time of measurements, leaf properties (species, leaf area, boundary layer conductance, leaf temperature, net CO2 assimilation rate, stomatal conductance, internal CO2 concentration), and environmental conditions (Photosynthetic Photon Flux Density (PPFD), air temperature, CO2 concentration, relative humidity, air vapor pressure). 1.5 Discussion The overall project goal was to investigate the interactions between single leaf (or shoot) gas exchange properties and leaf (or shoot) optical properties. Leaf-level gas exchange measurements were made in the field on the dominant broadleaf and coniferous woody plant species growing in the SSA. The primary focus was on Populus tremuloides (aspen) at the SSA Young Aspen (YA) site and Pinus banksiana (jack pine) at the SSA Young Jack Pine (YJP) site. Measurements were also obtained from Picea mariana (black spruce) at the SSA Old Black Spruce (OBS) site, old Populus tremuloides (old aspen) and Picea glauca (white spruce) at the SSA Mixed site (MIX), old aspen and Corylus cornuta Marsh (hazelnut) from the SSA Old Aspen (OA) site, and hazelnut and Populus balsamifera (balsam- poplar) from the SSA-YA site. 1.6 Related Data Sets BOREAS TE-04 Gas Exchange Data from Boreal Tree Species BOREAS TE-05 Leaf Gas Exchange Data BOREAS TE-12 Leaf Optical Data for SSA Species BOREAS TE-12 SSA Water Potential Data BOREAS TE-12 SSA Shoot Geometry Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Timothy J. Arkebauer, Associate Professor 2.2 Title of Investigation Radiation and Gas Exchange of Canopy Elements in a Boreal Forest. 2.3 Contact Information Contact 1 Dr. Timothy J. Arkebauer Department of Agronomy University of Nebraska Lincoln, NE USA (402) 472-2847 Contact 2 Shelaine Curd Raytheon STX Corp. NASA GSFC Greenbelt, MD (301) 286-2447 (301) 286-0239 (fax) shelaine.curd@gsfc.nasa.gov Contact 3 Andrea Papagno Raytheon STX Corp. NASA GSFC Greenbelt, MD (301) 286-3134 (301) 286-0239 (fax) apapagno@pop900.gsfc.nasa.gov 3. Theory of Measurements Gas exchange measurements were made using an LI-6200 CO2 Infrared Gas Analyzer (IRGA) system in the closed-circuit mode. The net CO2 assimilation rate is calculated via the change in CO2 concentration in the sample chamber with time. Stomatal conductance is calculated from the rate of change of water vapor concentration with time, the fraction of the total system flow through the desiccant, and the (previously determined) boundary layer conductance of the leaf. Further details can be found in the LI-6200 Technical Reference Manual (LI-COR, Inc., 1990). Internal CO2 concentrations of the leaves were calculated based on the measured net CO2 assimilation rates and leaf conductances. Additional information on the theory related to leaf gas exchange measurements can be found in Ball (1987). 4. Equipment 4.1 Instrument Description 4.1.1 Collection Environment All gas exchange measurements were made on intact plants in the field at the various SSA sites mentioned in Section 1.5. 4.1.2 Source/Platform In most cases, measurements were made from the ground. At the SSA-OA, SSA-MIX, and SSA-OBS sites, measurements were made at the top of the Terrestial Ecology (TE) scaffold towers. 4.1.3 Source/Platform Mission Objectives Not applicable. 4.1.4 Key Variables Leaf properties: net CO2 assimilation rate, stomatal conductance, internal CO2 concentration, leaf temperature. Environmental conditions: air temperature, air vapor pressure, incident PPFD, air CO2 concentration. 4.1.5 Principles of Operation Measurements were made with an LI-6200 Portable Photosynthesis System operated in the closed mode. Net CO2 assimilation rate was determined from the time rate of change of CO2 concentration in the sample chamber. Stomatal conductance was determined from the time rate of change of water vapor concentration in the chamber, in conjunction with the fraction of the system flow diverted through the desiccant and the (previously determined) leaf boundary layer conductance. CO2 concentrations are measured with an IRGA. A pump circulates the air from the sample chamber, through the analyzer, and back into the sample chamber. Water vapor concentrations in the sample chamber are determined by a Vaisala humidity chip and a thermistor sensing the air temperature. Leaf temperatures are determined by a thermocouple pair that measures the temperature difference between the air thermistor and a thermocouple appressed to the leaf. Additional information is found in the LI-COR LI-6200 Technical Reference Manual. 4.1.6 Sensor/Instrument Measurement Geometry None. 4.1.7 Manufacturer of Instrument LI-6200 CO2 Gas IRGA LI-COR, Inc. P.O. Box 4425 4421 Superior Street Lincoln, NE 68504 USA (402) 467-3576 (402) 467-2819 (fax) 4.2 Calibration 4.2.1 Specifications The IRGAs, the humidity chips, the flow meters, and the quantum sensors were calibrated by the manufacturer prior to each field season. The zero and span of the LI-6200 CO2 analyzer were calibrated against known standard gases in the field. 4.2.1.1 Tolerance None. 4.2.2 Frequency of Calibration Annual calibration of the IRGAs, the humidity chips, the flow meters, and the quantum sensors was done by the manufacturer. Daily calibration of the zero and span of the IRGAs was performed in the field. The CO2 zero and the flow meter zero were checked and adjusted several times daily. 4.2.3 Other Calibration Information Calibration gases for the IRGAs were obtained from Acklands, 1042 Quebec Ave., Saskatoon, Saskatchewan CANADA, S7K 1V5 (Primary supplier: Linde Gas, Alberta, CANADA). These gases were calibrated against gases of known concentration traceable to the National Oceanic and Atmospheric Administration (NOAA), Boulder, CO. 5. Data Acquisition Methods Samples from the coniferous species (e.g., Pinus banksiana, Picea mariana) were excised immediately after gas exchange measurements for leaf area determination. Leaf areas (i.e., surface areas of the needles enclosed in the gas exchange cuvette) were determined at the Paddockwood School Laboratory in the evening following the daily field work. A positive net CO2 assimilation rate (e.g. photosynthesis) means that the net flux of CO2 is into the leaf. A negative net CO2 assimilation rate (e.g., respiration) indicates that the net flux of CO2 is out of the leaf. Measurements of leaves from the broadleaf species (Populus tremuloides, Populus balsamifera, and Corylus cornuta) were made by enclosing entire leaves, or portions thereof, inside the sample cuvette. Small shoots of the coniferous species (Pinus banksiana, Picea mariana, Picea glauca), consisting of a number of needles, were placed into the sample cuvette for gas exchange determination. The coniferous samples consisted of needles from one age class only. The other age class needles were either excluded from the cuvette or were clipped off from the branch. The LI-6200 measurements were made with either a 0.25-liter or a 1-liter sample chamber. Most measurements were made under natural illumination (sunlight); however, a limited number of measurements were made with an incandescent light source in conjunction with a dichroic mirror. Leaves to be measured were placed in the sample chamber without altering their original orientation. The sample chamber was held with a tripod standing on the soil (or scaffold) surface. Light response curves were usually made by attenuating natural illumination with neutral density filters. Respiration rates were determined after enclosing leaves in an opaque film-changing bag. Assimilation rate versus internal CO2 concentration responses were determined using a transient technique. The net CO2 assimilation rate and the internal CO2 concentrations for these studies were corrected for chamber leaks, and an external fan was used to moderate chamber temperatures (for details see McDermitt et al., 1989). Leaf areas for the broadleaf species were determined by tracing the leaf outline on ruled graph paper. Leaf areas for the coniferous species were determined by the volume displacement method. Shoots were submerged in a water-filled container (containing 3-5% detergent in order to wet all surfaces) and the volume of water they displaced was recorded. The displaced volume was proportional to the total surface area of the shoot (see below). All gas exchange values are expressed on half the total surface area of the sample (for the broadleaf species this is the area projected normal to the leaf surface). 6. Observations 6.1 Data Notes None. 6.2 Field Notes A limited set of field notes and observations is available by request from T.J. Arkebauer. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The measurement sites and associated North American Datum 1983 (NAD83) coordinates are: SSA-YA canopy access tower, site id D0H4T, Lat/Long: 53.65601 N, 105.32314 W, Universal Transverse Mercator (UTM) Zone 13, N:5,945,298.9, E:478,644.1 SSA-OA canopy access tower located 100 m up the path to the flux tower site, site id C3B7T, Lat/Long: 53.62889 N, 106.19779 W, UTM Zone 13, N:5,942,899.9 E:420,790.5 SSA-OBS canopy access tower located at flux tower site, site id G8I4T, Lat/Long: 53.98717 N, 105.11779 W, UTM Zone 13, N:5,982,100.5E;492,276.5 SSA-MIX canopy access tower, site id D9I1M, Lat/Long: 53.7254 N, 105.20643 W, UTM Zone 13, N:5,952,989.7, E:486,379.7 SSA-YJP near flux tower site, site id F8L6T, Lat/Long: 53.87581 N, 104.64529 W, UTM Zone 13, N:5,969,762.5 E:523,320.2 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution These data are point source measurements at the given locations. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Measurements were made from 29-May-1994 through 8-Sep-1994 and from 1-Jul-1995 through 7-Aug-1995. For each species and each year, data are arranged chronologically in the data file. 7.2.2 Temporal Coverage Map None given. 7.2.3 Temporal Resolution Multiple measurements were made at the SSA-YA, SSA-OA, SSA-OBS, SSA-MIX, and SSA-YJP sites on several days per month from 29-May-1994-8-Sep-1994 and from 1- Jul-1995 through 7-Aug-1995. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (te12lgex.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (te12lgex.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS TE-12 Leaf Gas Exchange Data are contained in one dataset. 8.2 Data Format(s) The data files contain a series of numerical and character fields of varying length separated by commas. The character fields are enclosed in single apostrophe marks. Sample data records are shown in the companion data definition file (te12lgex.def). 9. Data Manipulations 9.1 Formulae None. 9.1.1 Derivation Techniques and Algorithms The total surface area of the conifer samples was calculated by: SA = X(VNL) 0.5 (1) where: X is a shape factor. V is the displaced volume. N is the number of needles in the sample. L is the average needle length. L was determined for each sample using a subset of 10 needles. X was determined from a random sample of 35 needles. Values of X were 4.36 for Pinus banksiana and 4.00 for Picea mariana and P. glauca. Formulae for calculating the net CO2 assimilation rates, stomatal conductances, and internal CO2 concentrations are given in the LI-6200 Technical Reference Manual. 9.2 Data Processing Sequence 9.2.1 Processing Steps None given. 9.2.2 Processing Changes None given. 9.3 Calculations 9.3.1 Special Corrections/Adjustments Not applicable. 9.3.2 Calculated Variables Not applicable. 9.4 Graphs and Plots Not applicable. 10. Errors 10.1 Sources of Error Calibration drift: The flow meter zero and IRGA CO2 zero exhibited occasional drifts. The zeros were set periodically throughout the day. Dew/wetness: When leaves were wet, the stomatal conductance and internal CO2 values may not be correct. Examples of spurious data include conductances less than zero and CO2 concentrations in the thousands. 10.2 Quality Assessment None given. 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. 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data Other than the few times measurements were made on moist leaves (as discussed above), there are no known problems with the data set. 11.3 Usage Guidance The normal caveat of 'use at your own risk' applies. Correspondence with T.J. Arkebauer is encouraged when questions arise. 11.4 Other Relevant Information Ms. Litao Yang was responsible for most of the day-to-day coordination of the field measurements. Mr. Runsheng Xu assisted with field data collection in 1994. Their assistance was greatly appreciated. 12. Application of the Data Set These data can be used to study the gas exchange of boreal vegetation. 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 TE-12 leaf 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 LI-6200 Technical Reference Manual, LI-COR, Inc., Lincoln, NE, USA, March 1990. 17.2 Journal Articles and Study Reports Ball, J.T. 1987 Calculations related to gas exchange. In: Stomatal Function. E. Zeiger, G.D. Farquhar and I.R. Cowan (eds), Stanford University Press, Stanford, CA, pp. 446-475. McDermitt, D.K., J.M. Norman, J.T. Davis, T.M. Ball, T.J. Arkebauer, J.M. Welles, and S.R. Roemer. 1989 CO2 response curves can be measured with a field- portable closed-loop photosynthesis system. Ann. Sci. For. 46:416s-420s. 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 results, and future directions. JGR, BOREAS Special Issue, 102 (D24), 28731-28769. 17.3 Archive/DBMS Usage Documentation None. 18. Glossary of Terms None. 19. List of Acronyms ASCII - American Standard Code for Information Interchange BOREAS - BOReal Ecosystem-Atmosphere Study BORIS - BOREAS Information System CO2 - carbon dioxide DAAC - Distributed Active Archive Center EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center IRGA - Infrared Gas Analyzer MIX - Mixed NAD83 - North American Datum of 1983 NIR - Near Infrared Radiation NOAA - National Oceanic and Atmospheric Administration NSA - Northern Study Area OA - Old Aspen OBS - Old Black Spruce OJP - Old Jack Pine ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park PAR - Photosynthetically Active Radiation PPFD - Photosynthetic Photon Flux Density SSA - Southern Study Area TE - Terrestrial Ecology TF - Tower Flux site URL - Uniform Resource Locator UTM - Universal Transverse mercator YA - Young Aspen YJP - Young Jack Pine 20. Document Information 20.1 Documentation Revision Date Written: 30-Jun-1997 Last Updated: 30-Mar-1999 20.2 Document Review Date(s) BORIS Review: 15-Jul-1998 Science Review: 21-Jul-1998 20.3 Document ID 20.4 Citation T.J. Arkebauer and L. Yang at the Department of Agronomy of the University of Nebraska in Lincoln, NE. Please contact investigators listed in Section 2.3, Contact Information. 20.5 Document Curator 20.6 Document URL Keywords: leaf gas exchange respiration boundary layer conductance leaf temperature TE12_Leaf_Gas_Exch.doc 05/07/99