BOREAS TF-09 SSA-OBS Branch Level Flux Data Summary The BOREAS TF-09 team collected data which describe carbon dioxide and water vapor fluxes from foliage at the BOREAS SSA-OBS site from 07-April through 23- November-1996. The data are available in tabular ASCII files. Table of Contents 1. Data Set/Model 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/Model 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 TF-09 SSA-OBS Branch Level Flux Data 1.2 Data Set Introduction A system of large cuvettes was used to measure whole branch CO2 and H2O vapor exchange of four black spruce (Picea mariana [Mill] BSP) branches at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) Old Black Spruce (OBS) site. 1.3 Objective/Purpose The objective of this study was to measure and model the CO2 exchanges of boreal black spruce forest branches over the course of an entire growing season. These measurements will be used to parameterise models and to assist scaling up procedures from leaf level to stand level (eddy covariance) measurements. 1.4 Summary of Parameters and Variables Measurements include CO2 and H2O fluxes, photosynthetic photon flux density (PPFD), air and leaf temperatures, relative humidity, air humidity deficit, and CO2 concentration. 1.5 Discussion The branch bags consisted of two 5-mm-thick acrylic end pieces, oval in shape (600-mm major axis, 300 mm minor axis, 0.14-m2 area), separated by five thin (5 mm diameter) stainless steel rods. One end was made such that it could slide up or down the rods in order to adjust the bag length to suit the individual branch. An ovaloid shape was chosen to minimize dead volume within the bag, to minimize the bag's surface area to volume ratio (minimizing any adsorption/desorption effects), to minimize attenuation of incoming light, and for aesthetic reasons. The bag itself was effected by covering the structure with polypropylene film (ICI Propafilm, 34-mm thickness, ICI PLC, London) and sealing along the edge of the end piece with silicone sealant. The bottom of the bag was left unsealed to allow placement of the bag upon the branch; afterward, it and the branch entry point were sealed in a similar fashion. A 12-volt electric fan (RS 583-050, RS Components Ltd., Northants) was mounted at the trunk end of each bag, and blew air at a high flow rate (40 dm3 s-1, approximately 18 to 26 air changes min-1) through the bag via large shrouded inlet and outlet ports. When a gas exchange measurement was to be made, the ventilation fan was switched off, thin flap valves dropped over the inlet and outlet and were shut tight with small electromagnets, and an internal circulating fan was switched on. Air was circulated (5 dm3 min-1) at all times between all bags and the box containing the infrared gas analyzer (IRGA) and control system through loops of tubing (5-mm i.d. Dekabon, Furon, Gembioux, Belgium), and at measurement time a small amount of air (0.2 dm3 min-1) was diverted from the appropriate loop to the IRGA (LI-6262, LI-COR Inc., Lincoln, NE) operating in absolute mode. Within each bag, relative humidity and air temperature were measured (Vaisala HMB 30A, Vaisala (UK) Ltd., Cambridge), as was leaf temperature (thin Cu-Con thermocouple referenced to the air temperature sensor) and, for a period, bag internal vs. external temperature (Cu-Con thermocouple). Light incident upon each branch was measured with a Macam light sensor (Macam SD101QV, Macam, Livingstone) mounted directly onto the branch, midway along its length. Sensor outputs were recorded through a Campbell AM416 multiplexer to a Campbell CR21X data logger (Campbell Scientific Ltd., Shepshed, Leics.), which also initiated the measurement sequence. Each bag was closed for 5 minutes in turn, during which time the sensors were read every 20 seconds; thus, each bag was measured every 20 minutes. Gas exchange was calculated from the slope of the regression of gas concentration upon time (excluding the readings from the initial 40 s for CO2 and the initial 80 s for H2O vapor in order to ensure that the IRGA was entirely flushed of the previous sample) and the volume of the system (106.3, 134.3, 91.9, and 106.3 dm3 for bags 1 to 4, respectively). The air sample bleed to the IRGA during the measurement period was negligible (~1 dm3) compared to the bag volume and was ignored in calculations. All bags were leak tested by shading the branch to its light compensation point, blowing into the bag to create a high internal/external concentration differential, closing the inlet and outlet ports, and monitoring bag concentration over a period of time. 1.6 Related Data Sets BOREAS TF-09 SSA-OBS Tower Flux, Meteorological, and Soil Temperature Data BOREAS TE-11 SSA-OJP Branch Level Flux Data BOREAS TE-12 Leaf Photosynthesis Data BOREAS TE-10 Leaf Photosynthesis Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Mr. Mark B. Rayment & Prof. Paul G. Jarvis Institute of Ecology and Resource Management University of Edinburgh UK 2.2 Title of Investigation The CO2 Exchanges of Boreal Black Spruce Forest 2.3 Contact Information Contact 1 --------- Mr. Mark B. Rayment Institute of Ecology and Resource Management University of Edinburgh Edinburgh UK +131 650 5423 +131 662 0478 (fax) M.Rayment@ed.ac.uk Contact 2 ------------- K. Fred Huemmrich University of Maryland NASA GSFC Greenbelt, MD (301) 286-4862 (301) 286-0239 (fax) Karl.Huemmrich@gsfc.nasa.gov 3. Theory of Measurements The net carbon uptake of a tree depends on the assimilation of carbon dioxide by photosynthesis in the leaves and the carbon dioxide emissions resulting from respiratory processes in the leaves and woody tissues of the tree. Transpiration of water occurs mainly from the foliage. Enclosures surrounding branches remain open for the majority of the time and are periodically closed, at which time the rate of change of gas concentration allows calculation of an integrated measure of the net exchange of gases between the branch and the atmosphere. 4. Equipment 4.1 Sensor/Instrument Description 4.1.1 Collection Environment Measurements were collected from early April through late November; temperatures ranged from below freezing to over 30 °C during that period. 4.1.2 Source/Platform The branch bags surrounded individual spruce branches. The bags were supported in position by elastic ropes attached to the trunk above the bag and, where necessary, to a support projecting from the canopy access tower. This arrangement allowed the bags to move freely as the trees and branches moved with the wind. Each of the bags was positioned on a south-facing branch to minimize shading by the tower. The bags could be reached from the canopy access tower, made of 5- by 9-foot scaffolding. Instruments: Gas concentration: IRGA LI-6262 (LI-COR Inc., Lincoln, NE) operating in absolute mode. Relative humidity and air temperature: Vaisala HMB 30A (Vaisala (UK) Ltd., Cambridge). Leaf temperature: thin Cu-Con thermocouple referenced to the air temperature sensor. Incident PPFD: Macam SD101QV light sensor mounted directly onto the branch, midway along its length. Logger: Campbell AM416 multiplexer and Campbell CR21X data logger. Tubing: 5-mm i.d. Dekabon. 4.1.3 Source/Platform Mission Objectives The objective was to measure branch scale CO2 and water vapor fluxes and related environmental variables in black spruce at the southern edge of the boreal forest. 4.1.4 Key Variables CO2 and water vapor fluxes. Supporting meteorological variables: PPFD, air temperature, leaf temperature, CO2, water vapor concentration. 4.1.5 Principles of Operation The LI-COR LI-6262 IRGA is a closed-path instrument with reference and sample cells with an infrared source at one end and a detector at the other. Different gases absorb infrared of different frequencies, and filters are used to select a narrow band that corresponds to an absorption band of the gas of interest. The LI-6262 measures CO2 and H2O concentrations. A gas of known concentration is passed through a reference cell, and the gas whose concentration is to be measured is passed through the sample cell. The amount of infrared reaching the detector in each cell is a function of the gas concentration in the cell. The difference in voltage produced by the detectors of the reference and sample cells is then a function of the difference in concentration of the gas in the cells. Other sensors were common meteorological sensors used in a standard fashion. For principles of operations of these sensors, please see a relevant textbook; e.g., Pearcy et al. (1991). 4.1.6 Sensor/Instrument Measurement Geometry Two branch bags were installed on each of two trees at the SSA-OBS site in early April 1996. Two bags were positioned in the upper canopy (at 7.85 m above the ground for branch number 1 and 8.25 m for branch number 3) and two in the lower canopy (at 5.22 m for branch number 2 and 5.48m for branch number 4); the trees' DBH were 10 cm and 9 cm. The bags were supported in position by elastic ropes attached to the trunk above the bag and, where necessary, to a support projecting from the canopy access tower. This arrangement allowed the bags to move freely as the trees and branches moved with the wind. Each of the bags was positioned on a south-facing branch to minimize shading by the tower. Humidity, air and leaf temperatures, and PPFD were measured within the bag, close to or in contact with the leaves. Gas concentration was measured on a sample of air circulated between the bag and the IRGA. The IRGA was positioned in an insulated box mounted on the canopy access tower. 4.1.7 Manufacturer of Instrument Licor LI-6262 P.O. Box 4425/4421, Superior Street, Lincoln, NE 68504 USA Vaisala HMB 30A Vaisala (UK) Ltd., Cambridge UK Macam SD101QV light sensor Macam Livingstone UK Campbell AM416 multiplexer and Campbell CR21X data logger Campbell Scientific P. O. Box 551, Logan, UT 84321 USA Dekabon tubing J. P. Deane & Co. Ltd., 91, Ormonde Crescent, Glasgow G44 3SW UK 4.2 Calibration 4.2.1 Specifications LI-6262: The output linearization of this instrument was calibrated by the manufacturer and was last performed in July 1993. The field calibration fixes the lower and upper ends of the linearization function and is carried out by passing CO2 and water vapor free air through the reference cell (the instrument is used in the absolute mode) and setting the CO2 and water vapor channels to zero. The upper point is set by passing dry air of known CO2 or of known water vapor concentration through the sample cell and adjusting the appropriate channel to read the correct value. CO2 standard gases were cross-referenced to the BOREAS primary standards, and a LI-COR LI-610 dewpoint generator was used to produce air of known water vapor density. The Vaisala temperature and humidity probes either were bought new or were returned to the manufacturer for calibration immediately prior to installation. The Macam PPFD sensors were purchased new immediately prior to installation, and the manufacture's calibration factors were used. All bags were leak tested by shading the branch to its light compensation point, blowing into the bag to create a high internal/external concentration differential, closing the inlet and outlet ports and monitoring bag concentration over a period of time. The LI-6262 was usually calibrated every 4 to 7 days. Typical CO2 drift was 1- ppm drift in span and offset. Typical drift for the water vapor was 0.1 kPa in span and offset. 4.2.1.1 Tolerance None. 4.2.2 Frequency of Calibrations The LI-6262 was usually calibrated every 4 to 7 days. 4.2.3. Other Calibration Information None. 5. Data Acquisition Methods When a gas exchange measurement was to be made, the ventilation fan was switched off, thin flap valves dropped over the inlet and outlet and were shut tight with small electromagnets, and an internal circulating fan was switched on. Air was circulated (5 dm3 min-1) at all times between all bags and the box containing the IRGA and control system through loops of tubing, and at measurement time a small amount of air (0.2 dm3 min-1) was diverted from the appropriate loop to the IRGA operating in absolute mode. Within each bag, relative humidity and air temperature were measured, as was leaf temperature and, for a period, bag internal vs. external temperature. Light incident upon each branch was measured with a Macam light sensor mounted directly onto the branch, midway along its length. Each bag was closed for 5 minutes in turn, during which time the sensors were read every 20 seconds; thus, each bag was measured every 20 minutes. Gas exchange was calculated from the slope of the regression of gas concentration upon time (excluding the readings from the initial 40 s for CO2 and the initial 80 s for H2O vapor in order to ensure that the IRGA was entirely flushed of the previous sample) and the volume of the system (106.3, 134.3, 91.9, and 106.3 dm3 for bags 1 to 4, respectively). The air sample bleed to the IRGA during the measurement period was negligible (~1 dm3) compared to the bag volume and was ignored in calculations. A Campbell Scientific 21x data logger was used to log the data together with a Campbell AM416 multiplexer. The raw signal from each sensor was converted into the appropriate units in the data logger program. The data logger also initiated the measurement sequence. 6. Observations 6.1 Data Notes Values given are on a PROJECTED leaf area basis; that is, values should be adjusted by a shape factor to express rates on a total surface or hemisurface area basis. For black spruce, hemisurface area was last reported to be 1.27 x projected area; i.e., these rates would be divided by 1.27 to given rates on a hemisurface area basis. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage All data were collected at the BOREAS SSA-OBS site. North American Datum 1983 (NAD83) coordinates for this site are latitude 53.98717° N, longitude 105.11779° W, and elevation of 628.94 m. Branches had total projected needle areas of 3115, 2014, 1657, and 2342 cm2, for chambers one through 4, respectively. 7.1.2 Spatial Coverage Map None. 7.1.3 Spatial Resolution The values are point measurements from trees near the locations given in Section 7.1.1. 7.1.4 Projection None. 7.1.5 Grid Description None. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage The data were collected from 06-April to 22-November-1996. Data were collected continuously with gaps between 18- and 26-June and 03- and 07-July. 7.2.2 Temporal Coverage Map All data were collected at the BOREAS SSA-OBS site. 7.2.3 Temporal Resolution Each observation took 5 minutes to complete data collection cycled through each of the four bags so that observations of any given bag occur every 20 minutes. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf9brflx.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf9brflx.def). 8. Data Organization 8.1 Data Granularity All of the SSA-OBS Branch Level Flux Data are contained in one dataset. 8.2 Data Format The data files contain numerical and character fields of varying length separated by commas. The character fields are enclosed with single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition file (tf9brflx.def). 9. Data Manipulations 9.1 Formulae None. 9.1.1 Derivation Techniques and Algorithms None. 9.2 Data Processing Sequence A linear fit was made between the gas concentrations and time; data were rejected if the sum of the squares of the residuals was less than 0.9 and the calculated flux was non zero. 9.2.1 Processing Steps BORIS staff processed these data by: 1) Reviewing the initial data files and loading them online for BOREAS team access. 2) Designing relational data base tables to inventory and store the data. 3) Loading the data into the relational data base tables. 4) Working with the team to document the data set. 5) Extracting the data into logical files. 9.2.2 Processing Changes None. 9.3 Calculations Flux calculations: flux = (concentration change * molar volume)/(time interval * leaf area) 9.3.1 Special Corrections/Adjustments None. 9.3.2 Calculated Variables None. 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error Major sources of error include sensor drift, measurement of branch bag volume, and measurement of leaf area. 10.2 Quality Assessment 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 to check for spikes, values that are four standard deviations from the mean, long periods of constant values, and missing data. 11 Notes 11.1 Limitations of the Data Potential users of these data should be aware of the limitations of gas exchange as a means of investigating photosynthesis and of the implications of these measurements having been made on entire, enclosed branches. 11.2 Known Problems with the Data All known bad data have been removed from the files. 11.3 Usage Guidance Potential users of these data should be aware of the limitations of gas exchange as a means of investigating photosynthesis and of the implications of these measurements having been made on entire, enclosed branches. They should also be aware that these data have been submitted to BORIS out of courtesy rather than contractual obligation and should therefore seek the permission of the investigators before publishing analyses derived from them. These data remain the property of the University of Edinburgh and of the UK Natural Environment Research Council. 11.4 Other Relevant Information None. 12. Application of the Data Set This data set is useful for the examination of effects of environmental variables on photosynthesis and transpiration at the scale of individual branches. 13. Future Modifications and Plans Although these data represent the most recent data set, believed to be error free, some data might, in the future, be found to be in error. 14. Software 14.1 Software Description Logger program written with Campbell PC208. Flux and humidity-based calculations and initial screening of the data were carried out with a program written in Microsoft Visual Basic. Final data screening was carried out in SAS. 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 These 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 The data are available as tabular American Standard Code for Information Interchange (ASCII) text files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None 17.2 Journal Articles and Study Reports Pearcy, R.W., J. Ehleringer, H. A. Mooney, and P. W. Rundel. 1991. Plant Physiological Ecology: Field methods and instrumentation. Chapman and Hall, London and New York. Rayment, M.B. 1998. Ph.D. Thesis. University of Edinburgh. 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 (OPS DOC 94). Sellers, P., 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 (OPS DOC 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. Journal of Geophysical Research 102 (D24): 28,731-28,770. 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 DAAC - Distributed Active Archive Center DBH - Diameter at Breast Height EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center IRGA - Infra-Red Gas Analyzer NASA - National Aeronautics and Space Administration NSA - Northern Study Area ORNL - Oak Ridge National Laboratory OBS - Old Black Spruce PANP - Prince Albert National Park PPFD - Photosynthetic Photon Flux Density SSA - Southern Study Area TF - Tower Flux URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 25-Jun-1997 Revised: 06-Oct-1998 20.2 Document Review Date(s) BORIS Review: 23-Jul-1998 Science Review: 20.3 Document ID 20.4 Citation M.B.Rayment and P.G.Jarvis, Institute of Ecology and Resource Management, Edinburgh University. Users of these data should be aware that these data have been submitted to BORIS out of courtesy rather than contractual obligation and should therefore seek the permission of the investigators before publishing analyses derived from them. These data remain the property of the University of Edinburgh and of the UK Natural Environment Research Council. 20.5 Document Curator 20.6 Document URL Keywords BLACK SPRUCE PICEA MARIANA PHOTOSYNTHESIS RESPIRATION TRANSPIRATION TF09_BranchBag.doc 10/09/98