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