BOREAS TF-11 SSA Fen Soil Surface CO2 Flux Data Summary The BOREAS TF-11 team gathered a variety of data to complement their tower flux measurements collected at the SSA Fen site. These data are soil surface CO2 flux data at the SSA Fen site from 27-May-1994 to 23-Sep-1994 and from 13-May- 1995 to 3-Oct-1995. A portable gas exchange system was used to make these measurements. 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 1.1 Data Set Identification BOREAS TF-11 SSA Fen Soil Surface CO2 Flux Data 1.2 Data Set Introduction The Tower Flux-11 (TF-11) team collected soil surface CO2 flux data at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern Study Area (SSA) Fen site in 1994 and 1995. A portable gas exchange system was used to make these measurements. 1.3 Objectives/Purpose The objective of these measurements was to evaluate the soil surface CO2 flux and characterize its response to controlling variables (e.g., temperature, water content, water table depth). 1.4 Summary of Parameters Each data record includes the date and time of measurements, surface CO2 flux, and environmental conditions (air temperature, soil temperature, CO2 concentration, relative humidity, and air vapor pressure). 1.5 Discussion The overall project goal was to investigate the surface-atmosphere exchange of carbon dioxide and methane, and the associated energy fluxes, at the SSA Fen site. The exchange of CO2 at the soil surface is an important component of the overall surface-atmosphere CO2 exchange. It is related to soil (peat) decomposition processes, long-term carbon storage and, perhaps more indirectly, canopy photosynthesis. 1.6 Related Data Sets BOREAS TF-11 SSA Fen Tower Flux and Meteorological Data BOREAS TF-11 SSA Fen Leaf Gas Exchange Data BOREAS TF-11 SSA Fen 1995 Leaf Area Index Data BOREAS TF-11 SSA Fen 1996 Water Surface Film Capping Data 2. Investigator(s) 2.1 Investigator(s) Names and Titles Dr. Timothy J. Arkebauer, Associate Professor Department of Agronomy University of Nebraska-Lincoln Dr. Shashi B. Verma, Professor Department of Agricultural Meteorology University of Nebraska-Lincoln 2.2 Title of Investigation Field Micrometeorological Measurements, Process-Level Studies and Modeling of Methane and Carbon Dioxide Fluxes in a Boreal Wetland Ecosystem 2.3 Contact Information Contact 1 ----------- Dr. Timothy J. Arkebauer Department of Agronomy University of Nebraska Lincoln NE (402) 472-2847 Contact 2 ----------- David Knapp Raytheon ITSS NASA GSFC Greenbelt, MD (301) 286-1424 (301) 286-0239 (fax) David.Knapp@gsfc.nasa.gov 3. Theory of Measurements Surface CO2 flux measurements were made by using an LI-6200 system in the closed-circuit mode. An LI-6000-09 Soil Respiration Chamber was used with the system. The CO2 flux is calculated via the change in CO2 concentration in the sample chamber with time. Further details can be found in the LI-6200 Technical Reference Manual (LI-COR, Inc., 1990). Additional information on the general theory related to gas exchange measurements can be found in Ball (1987). 4. Equipment 4.1 Instrument Description The measurements were made with an LI-6200 Portable Photosynthesis System outfitted with an LI-6000-09 Soil Respiration Chamber. The chamber volume is approximately 1-liter, and it covers 83 cm2 of the soil surface. 4.1.1 Collection Environment All measurements were made under ambient environmental conditions in the field at the SSA Fen site. 4.1.2 Source/Platform Measurements were made from platforms or boardwalks raised approximately 0.2 m above the fen surface. 4.1.3 Source/Platform Mission Objectives None given. 4.1.4 Key Variables Soil surface CO2 flux, soil temperature, air temperature, air vapor pressure, air CO2 concentration, distance between soil surface and water table. 4.1.5 Principles of Operation The LI-6200 was operated in the closed mode. Surface CO2 fluxes were determined from the time rate of change of CO2 concentration in the LI-6000-09 chamber. CO2 concentrations are measured with an infrared gas analyzer (IRGA). A pump circulates the air from the respiration chamber, through the analyzer, and back into the chamber. Water vapor concentrations in the sample chamber are determined by a Vaisala humidity chip and a thermistor sensing the air temperature. Soil temperatures are determined by a thermocouple pair that measures the temperature difference between the air thermistor and a thermocouple inserted 10 cm below the soil surface. Additional information is found in the LI-COR LI-6200 Technical Reference manual, the LI-COR LI-6000-09 Soil Respiration Chamber instruction manual, and Norman et al. (1992). 4.1.6 Sensor/Instrument Measurement Geometry The measurements were made with an LI-6200 Portable Photosynthesis System outfitted with an LI-6000-09 Soil Respiration Chamber. The chamber volume is approximately 1-liter, and it covers 83 cm2 of the soil surface. 4.1.7 Manufacturer of Instrument 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 given. 4.2.2 Frequency of Calibration Annual calibration of the IRGAs, the humidity chips, the flow meters, and the quantum sensors were done by the manufacturer. Daily calibration of the zero and span of the IRGAs was done 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 The surface CO2 fluxes were measured at 48 collar locations (see Section 7.1.1). These collars were positioned in early May each year and were not moved during the growing season. When the water table covered a collar, the measurement was made at the water surface above the collar. For each surface flux determination, the LI-6000-09 chamber was first positioned atop the polyvinylchloride (PVC) collar such that a good seal was obtained. A tripod was used to hold the chamber in position. Fluxes were determined from the change of CO2 concentration inside the closed system. Care was taken to determine fluxes when the CO2 concentration in the chamber was near ambient (ca. 350 ppm); at times this meant drawing down the system CO2 concentration by using the LI-6200 soda lime scrubber. Once the chamber was in place, individual measurements took about 1-minute to complete. A negative surface CO2 flux (e.g., soil respiration) indicates that the net flux of CO2 is from the soil into the atmosphere. 6. Observations 6.1 Data Notes None given. 6.2 Field Notes A limited set of field notes and observations is available by request from T.J. Arkebauer (see Section 2.3). 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The SSA Fen is a “patterned” fen with a heterogenous surface. Areas of open water alternate with 2- to 20-cm-tall hummocks composed of more or less consolidated vegetation. Larger features include strings, where the peat surface is about 20-50 cm above the water table, and flarks, which are more extensive areas of open water. We attempted to characterize the variability in the surface CO2 flux associated with these microtopographic features as well as to obtain estimates of the surface CO2 flux in the vicinity of the micrometeorological tower. In mid-August 1993, two permanent boardwalks were laid out about 200 m north and south of the main (eddy correlation) boardwalk. Twelve measurement platforms were erected along each boardwalk to allow us access to the fen surface without standing on it. Six of these platforms (N1, N2, S1, S2, S5, and S6) were located on obvious (i.e., large) strings. (Note that these larger strings were, for the most part, absent from the “micrometeorological footprint” sensed by the eddy correlation sensors.) All the 1994 and 1995 surface flux data were obtained adjacent to these platforms. Platforms N3, N4, N5, N6, S3, and S4 were judged to be most representative of the micrometeorological tower footprint. These six platforms were all located in extensive areas of Betula pumila. The surface here consisted of sedge (Carex sp.) hummocks interspersed with open water where Menyanthes trifoliata was common. At the beginning of each season, 48 PVC collars (about 10 cm in diameter and 10 cm long) were placed near the 12 access platforms (four at each platform). Each of the four were positioned so that one collar was in a low spot, one was on a high spot, and two were in between. As the water table position changed during the season, the collars were alternately inundated and exposed. The SSA Fen tower was located at the following North American Datum of 1983 (NAD83) coordinates: Latitude Longitude BOREAS_X BOREAS_Y UTM Northing UTM Easting ------------------------------------------------------------------------- 53.80206N 104.61798W 419.527 330.991 5961566.6 525159.8 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution Each measurement represents the flux at a 10 cm diameter area near the SSA Fen tower site. 7.1.4 Projection These data were collected at point locations. 7.1.5 Grid Description None. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Measurements were made from 27-May-1994 to 23-Sep-1994 and from 13-May-1995 to 3-Oct-1995. 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution Measurements were taken at multiple times during the growing seasons. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf11soil.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf11soil.def). 8. Data Organization 8.1 Data Granularity All of the SSA Fen Soil Surface CO2 Flux Data are contained in one data set. 8.2 Data Format The data file contains 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 format shown in the companion data definition file (tf11soil.def). 9. Data Manipulations 9.1 Formulae Formulae for calculating the CO2 flux rates are given in the LI-6200 Technical Reference Manual. 9.1.1 Derivation Techniques/Algorithms None given. 9.2 Data Processing Sequence 9.2.1 Processing Steps 1. Data were received by BORIS from TF-11. 2. BORIS standardized the units and loaded data into the data base. 3. BORIS extracted data from database into ASCII files. 9.2.2 Processing Changes None. 9.3 Calculations None. 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 Calibration drift: The flow meter zero and IRGA CO2 zero exhibited occasional drifts. The zeros were set periodically throughout the day. 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 BORIS loaded the data into the data base and checked for any inconsistencies during loading. 11. Notes 11.1 Limitations of the Data None given. 11.2 Known Problems With The Data There were problems with the soil thermocouple probes used in 1994. All 1994 soil temperatures are indicated as missing values. The difficult-to-interpret 1994 soil temperatures may be available by special request from T.J. Arkebauer. 11.3 Usage Guidance The normal caveat of 'use at your own risk' applies. Correspondence with T.J. Arkebauer is encouraged when questions arise. A negative surface CO2 flux (e.g., soil respiration) indicates that the net flux of CO2 is from the soil into the atmosphere. 11.4 Other Relevant Information Dr. Evan C. Jolitz was responsible for much of the day-to-day coordination of the field measurements. Mr. Shawn Stevens and Mr. Tommi Peltovuori assisted in data collection in 1994. Their assistance is greatly appreciated. We also thank LI-COR, Inc., for their generous contribution of various prototypes of the LI-6000-09 respiration chambers. 12. Application of the Data Set These data can be used to better understand the soil CO2 flux at a typical fen in the boreal forest. 13. Future Modifications and Plans None. 14. Software 14.1 Software Description None given. 14.2 Software Access None given. 15. Data Access 15.1 Contact for Data Center/Data Access Information These BOREAS data are available from the Earth Observing System Data and Information System (EOS-DIS) 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 15.2 Procedures for Obtaining Data BOREAS data may be obtained through the ORNL DAAC World Wide Web site at http://www-eosdis.ornl.gov/ or users may place requests for data by telephone, electronic mail, or fax. 15.3 Output Products and Availability Requested data can be provided electronically on the ORNL DAAC's anonymous FTP site or on various media including, CD-ROMs, 8-MM tapes, or diskettes. The complete set of BOREAS data CD-ROMs, entitled "Collected Data of the Boreal Ecosystem-Atmosphere Study", edited by Newcomer, J., et al., NASA, 1999, are also available. 16. Output Products and Availability 16.1 Tape Products None. 16.2 Film Products None. 16.3 Other Products These data are available on the BOREAS CD-ROM series. 17. References 17.1 Platform/Sensor/Data Processing Documentation LI-6200 Technical Reference Manual. March 1990. LI-COR, Inc., Lincoln NE, USA. LI-6000-09 Instruction Manual, November 1993. LI-COR, Inc., Lincoln NE, USA. 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. Norman, J.M., R. Garcia, and S.B. Verma. 1992. Soil surface CO2 fluxes and the carbon budget of a grassland. Journal of Geophysical Research 97(D17): 18,845- 18,853. Sellers, P. and F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN-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. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, and K.F. Huemmrich. 1997. Boreal Ecosystem-Atmosphere Study: 1996 Operations. NASA BOREAS Report (OPS DOC 96). 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.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 CD-ROM - Compact Disk-Read-Only-Memory DAAC - Distributed Active Archive Center DOY - Day of the Year EOS - Earth Observing System EOSDIS - EOS Data and Information System GMT - Greenwich Mean Time GSFC - Goddard Space Flight Center IFC - Intensive Field Campaign IRGA - Infrared Gas Analyzer NAD83 - North American Datum of 1983 NASA - National Aeronautics and Space Administration ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park PPMV - Parts Per Million by Volume PVC - Polyvinylchloride SSA - Southern Study Area TF - Tower Flux URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 30-Jun-1997 Last Revised: 10-May-1999 20.2 Document Review Date(s) BORIS Review: 19-Apr-1999 Science Review: 20.4 Requested Form of Acknowledgment T.J. Arkebauer and E.C. Jolitz 20.5 Document Curator 20.6 Document URL Keywords: SOIL CO2 FLUX CARBON DIOXIDE TF11_Soil_Surf_CO2.doc 06/09/99