BOREAS TF-03 Automated Chamber CO2 Flux Data from the NSA-OBS Summary: The BOREAS TF-03 and TGB-01 teams collected automated CO2 chamber flux data in their efforts to fully describe the CO2flux at the NSA-OBS site. This data set contains fluxes of CO2 at the NSA-OBS site measured using automated chambers. In addition to reporting the CO2flux, it reports chamber air temperature, moss temperature, and light levels during each measurement. The data set covers the period from 23-Sep-1995 through 26-Oct-1995 and from 28-May-1996 through 21-Oct- 1996. 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 TF-03 Automated Chamber CO2 Flux Data from the NSA-OBS 1.2 Data Set Introduction This data set contains fluxes of carbon dioxide (CO2) at the BOReal Ecosystem- Atmosphere Study (BOREAS) Northern Study Area (NSA) Old Black Spruce (OBS) site measured using automated chambers. In addition to reporting the CO2 flux, it reports chamber air temperature, moss temperature, and light levels during each measurement. The data set covers the period from 23-Sep-1995 through 26-Oct- 1995 and from 28-May-1996 through 21-Oct-1996. The data are stored in tabular American Standard Code for Information Interchange (ASCII) files. 1.3 Objective/Purpose Black spruce forests with a continuous carpet of feather moss in shaded dry areas and sphagnum moss in open wet areas dominate much of the North American boreal zone. The exchange of CO2 between these forests and the atmosphere is complex, with important contributions by five physiological processes: black spruce photosynthesis, black spruce respiration, moss photosynthesis, moss respiration, and heterotrophic respiration. Information on the rates of and controls on each of these processes is needed to improve understanding of the current and future carbon balance of boreal forests. An automated, multiplexing gas-exchange system was used to make continuous, unattended measurements of the net exchange of CO2 at the moss surface at the NSA-OBS site. 1.4 Summary of Parameters The primary focus is on the net fluxes of CO2 measured. The data set also includes chamber air temperature, moss temperature, and light levels during each measurement. 1.5 Discussion Measurements were made at the NSA-OBS site. The system operated continuously and was visited every 2 weeks. The site was heterogeneous with large changes in vegetation over small gradients in elevation. Upland areas were dominated by dense, 10-m-tall, 120-year-old black spruce, with a minor shrub layer and continuous feather moss. Lower areas were dominated by sparse, 1- to 6-m-tall spruce and continuous sphagnum moss. For 1994, chambers 1-3 were placed in an upland area of well-developed feather moss, while chambers 8-10 were placed in a lower area dominated by sphagnum moss. The other chambers were placed at intermediate or lichen-covered locations. 1.6 Related Data Sets BOREAS TGB-01/TGB-03 CH4 Chamber Flux Data over the NSA Fen BOREAS TGB-03 Plant Species Composition Data over the NSA Fen BOREAS TGB-01/TGB-03 NEE Data over the NSA Fen BOREAS TGB-03 CH4 and CO2 Chamber Flux Data over NSA Upland Sites BOREAS TGB-01 NSA CH4 and CO2 Chamber Flux Data BOREAS TGB-01 CH4 Concentration and Flux Data from NSA Tower Sites BOREAS TGB-01 NSA SF6 Chamber Flux Data 2. Investigator(s) 2.1 Investigator(s) Name and Title Dr. Michael L. Goulden University of California Dr. Patrick M. Crill Research Associate Professor University of New Hampshire 2.2 Title of Investigation Automated Measurements of CO2 Exchange at the Moss Surface of a Black Spruce Forest. 2.3 Contact Information Contact 1 Dr. Michael L. Goulden Earth System Science Physical Sciences Research Facility University of California Irvine, CA (714) 824-1983 (office) (714) 824-8794 (department) (714) 824-3256 (fax) mgoulden@uci.edu Contact 2 Dr. Patrick M. Crill Institute for the Study of Earth, Oceans, and Space Complex Systems Research Center University of New Hampshire Durham, NH (603) 862-3519 (603) 862-0188 (fax) patrick.crill@unh.edu Contact 3 Sara Conrad Raytheon ITSS NASA GSFC Greenbelt, MD (301) 286-2624 (301) 286-0239 (fax) Sara.Conrad@gsfc.nasa.gov 3. Theory of Measurements Net exchange of CO2 above the moss surface reflects the sum of moss photosynthesis and moss, root, and heterotrophic respiration during daylight, and moss, root, and heterotrophic respiration at night. Long-term in situ measurements of CO2 exchange over diel courses should allow partial separation of these processes and permit an analysis of the associated environmental controls. However, investigations of this type have been limited by the difficulty of obtaining reliable field measurements in remote, inclement regions. 4. Equipment 4.1 Sensor/Instrument Description 4.1.1 Collection Environment Data were collected under all environmental conditions. 4.1.2 Source/Platform Ground. 4.1.3 Source/Platform Mission Objectives Support investigators and chambers. 4.1.4 Key Variables CO2 flux. 4.1.5 Principles of Operation Data were recorded and the system was managed with a datalogger. The raw CO2 and H2O signals were sampled every 2 seconds and averaged every minute. The other signals were sampled every 2 seconds and averaged every 9 minutes. 4.1.6 Sensor/Instrument Measurement Geometry Not applicable. 4.1.7 Manufacturer of Sensor/Instrument The chambers were 38 x 38.5 x 25 cm boxes built of clear lexan and aluminum angle. Thermocouple Omega Engineering Stamford, CT Datalogger Campbell Scientific Logan, UT Infrared gas analyzer (IRGA) IRGA, Model 6262 LI-COR, Inc Lincoln, NE 4.2 Calibration 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration Each chamber was calibrated at least once a day by standard addition. Every 21 hours, the system added 0.08 cm3/sec of 10% CO2 to the return flow throughout a 3-hour circuit. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods Measurements were made at the NSA-OBS site. The system operated continuously and was visited every 2 weeks. The site was heterogeneous with large changes in vegetation over small gradients in elevation. Upland areas were dominated by dense, 10-m-tall, 120-year-old black spruce, with a minor shrub layer and continuous feather moss. Lower areas were dominated by sparse, 1- to 6-m-tall spruce and continuous sphagnum moss. For 1994, chambers 1-3 were placed in an upland area of well-developed feather moss, while chambers 8-10 were placed in a lower area dominated by sphagnum moss. The other chambers were placed at intermediate or lichen-covered locations. Measurements of CO2 exchange above moss surfaces are sensitive to errors that are not usually encountered when working above bare soil. Moss is extremely porous, creating uncertainty in chamber volume and also increasing the risk of mass flow. Transient changes in moss physiology and in the direction of CO2 movement may confound dark respiration measurements made by shading during daytime. Because the physiological activity of moss is sensitive to water content, chambers that remain in place for extended periods must not alter evaporation or precipitation. Finally, the CO2 exchange above moss is complex, and therefore many measurements may be required to separate the environmental controls on photosynthesis and respiration. As a result of these and other uncertainties, discrepancies among methods used to measure moss-surface exchange in BOREAS have been large, and it is unclear which, if any, chamber design provides accurate results. The Tower Flux (TF)-03 team designed an automated gas-exchange system to circumvent most of these problems. The system sequentially sampled 10 clear, closed-type chambers, completing a circuit every 3 hours. Power consumption was less than 300 W at 115 VAC. The system was shipped and operated in three weather-tight boxes that sat on the forest floor within 15 m of the chambers. The tubing and mixing volume were flushed and allowed to equilibrate during the first 8 minutes of each run. The selected chamber was then closed slowly, and the change in CO2 monitored for the next 10 minutes. Chamber closure had no discernible effect on the temperature within a chamber during the fall of 1995. Subsequent measurements in midsummer 1996 revealed some warming (1-2 8C), which occasionally resulted in condensation on the walls of chambers exposed to direct sun. Air was drawn from the chamber throughout the run and passed through a CO2 and H2O IRGA operated in absolute mode. The flow through the IRGA was controlled at 80 cm3/second. The pressure of the sample flow was measured with a pressure transducer immediately after it had exited the IRGA and was assumed equal to the pressure in the sample cell. Soil temperature at 5 cm beneath the moss surface and air temperature were measured in each chamber with type-T thermocouples. Horizontal photosynthetically active photon flux density (PPFD) was measured at each chamber with a gallium arsenide phosphide photodiode. Data were recorded and the system managed with a datalogger. The raw CO2 and H2O signals were sampled every 2 seconds and averaged every minute. The other signals were sampled every 2 seconds and averaged every 9 minutes. The solenoids used for chamber selection, chamber closure, and calibration were controlled with a pair of 16-channel control modules. The set points for the mass flow controllers were provided by a four-channel analog output module. The signals from the thermocouples and light sensors were multiplexed with a thermally insulated 32-channel multiplexer. The data were transferred to a storage module every 3 hours and subsequently transferred to a computer every 2 weeks. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage All measurements were made at the NSA-OBS site. The North American Datum of 1983 (NAD83) coordinates at the site are 55.8798° N, 98.4848° W. 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution These are point measurements made 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 The data set covers the period from 23-Sep-1995 through 26-Oct-1995 and from 28- May-1996 through 21-Oct-1996. 7.2.2 Temporal Coverage Map Not available. 7.2.3 Temporal Resolution The CO2 and H2O signals were sampled every 2 seconds and averaged every minute. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf3acc02.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf3acc02.def). 8. Data Organization 8.1 Data Granularity All of the CO2 flux data are in one file. 8.2 Data Format(s) The data files contain American Standard Code for Information Interchange (ASCII) 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 (tf3acc02.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms None given. 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 None given. 9.3.2 Calculated Variables None given. 9.4 Graphs and Plots None given. 10. Errors 10.1 Sources of Error Measurements of CO2 exchange above moss surfaces are sensitive to errors that are not usually encountered when working above bare soil. Moss is extremely porous, creating uncertainty in chamber volume and also increasing the risk of mass flow. Transient changes in moss physiology and in the direction of CO2 movement may confound dark respiration measurements made by shading during daytime. Because the physiological activity of moss is sensitive to water content, chambers that remain in place for extended periods must not alter evaporation or precipitation. Finally, the CO2 exchange above moss is complex, and therefore many measurements may be required to separate the environmental controls on photosynthesis and respiration. As a result of these and other uncertainties, discrepancies among methods used to measure moss-surface exchange in BOREAS have been large, and it is unclear which, if any, chamber design provides accurate results. 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 for general consistency and clarity. 11. Notes 11.1 Limitations of the Data None given. 11.2 Known Problems with the Data See Section 10.1. 11.3 Usage Guidance See Section 10.1. 11.4 Other Relevant Information None given. 12. Application of the Data Set None given. 13. Future Modifications and Plans None given. 14. Software 14.1 Software Description None given. 14.2 Software Access Not applicable. 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 Comma-delimited ASCII text files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None given. 17.2 Journal Articles and Study Reports 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. 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 (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 EOS - Earth Observing System EOSDIS - EOS Data and Information System GSFC - Goddard Space Flight Center IRGA - Infrared Gas Analyzer NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration NSA - Northern Study Area OBS - Old Black Spruce ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Pike PPFD - Photosynthetically Active Photon Flux Density SSA - Southern Study Area TF - Tower Flux TGB - Trace Gas Biochemistry URL - Uniform Resource Locator SSA - Southern Study Area 20. Document Information 20.1 Document Revision Date Written: 08-Oct-1998 Last Updated: 14-Dec-1998 20.2 Document Review Date(s) BORIS Review: 15-Oct-1998 Science Review: 20.3 Document ID 20.4 Citation Goulden, M.L. and Crill, P.M. 1997. Automated measurements of CO2 exchange at the moss surface of a black spruce forest. Tree Physiology. 17:537-542. 20.5 Document Curator 20.6 Document URL Keywords: Carbon Dioxide flux PPFD Feather Moss Sphagnum Moss Black Spruce TF03_Automated.doc 01/13/99