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