BOREAS TE-09 In Situ Diurnal Gas Exchange of NSA Boreal Forest Stands

Summary

The purpose of the BOREAS TE-09 study was threefold: 1) to provide in situ gas 
exchange data that will be used to validate models of  photosynthetic  responses 
to light, temperature, and carbon dioxide (CO2); 2) to compare the 
photosynthetic responses of different tree crown levels (upper and lower); and 
3) to characterize the diurnal water potential curves for these sites to get an 
indication of the extent to which soil moisture supply to leaves might be 
limiting photosynthesis.

The gas exchange data of the BOREAS NSA were collected to characterize diurnal 
gas exchange and water potential of two canopy levels of five boreal canopy 
cover types: young jack pine, old jack pine, old aspen, lowland old black 
spruce, and upland black spruce. These data were collected between 27-May-1994 
and 17-Sep-1994.  The data are provided 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 TE-09 In Situ Diurnal Gas Exchange of NSA Boreal Forest Stands

1.2 Data Set Introduction

The gas exchange data of the BOReal Ecosystem-Atmosphere Study (BOREAS) Northern 
Study Area (NSA) were collected to characterize diurnal gas exchange and water 
potential of two canopy levels of five boreal canopy cover types:
young and old jack pine (Pinus banksiana Lamb.), old aspen
(Populus tremuloides Michx.), and lowland and upland black spruce (Picea mariana 
(Mill) B.S.P.).  These data were collected between 27-May-1994 and 17-Sep-1994.

1.3 Objective/Purpose

The purpose of this study was threefold:  1) to provide in situ gas exchange 
data that will be used to validate models of  photosynthetic  responses to 
light, temperature, and carbon dioxide (CO2); 2) to compare the photosynthetic 
responses of different tree crown levels (upper and lower), and 3) to 
characterize the diurnal water potential curves for these sites to get an 
indication of the extent to which soil moisture supply to leaves might be 
limiting photosynthesis.

1.4 Summary of Parameters

Net photosynthesis, stomatal conductance to water vapor, stomatal conductance to 
CO2 , transpiration, water use efficiency, mesophyll conductance, 
photosynthetically active radiation (PAR), air and leaf temperature, CO2 
concentration, relative humidity, vapor pressure, vapour pressure deficit (VPD), 
barometric pressure, and water potential.

1.5 Discussion

The gas exchange data of the BOREAS NSA were collected to characterize diurnal 
gas exchange and water potential of two canopy levels of five boreal canopy 
cover types: young and old jack pine, old aspen, lowland old upland black 
spruce. These data were collected between 27-May-1994 and 17-Sept-1994.

1.6 Related Data Sets

BOREAS TE-09 PAR and Leaf Nitrogen Data for BOREAS NSA Species
BOREAS TE-09 NSA Photosynthetic Capacity and Foliage Nitrogen Data
BOREAS TE-09 NSA Leaf Chlorophyll Density
BOREAS TE-09 NSA Photosynthetic Response Data

2. Investigator(s)

2.1 Investigator(s) Name and Title

Hank Margolis, Ph.D.
Universite Laval 
Faculte de foresterie et geomatique 
Pavillon Abitibi-Price  

2.2 Title of Investigation

Relationship between measures of absorbed and reflected radiation and the 
photosynthetic capacity of boreal forest canopies and understories.

2.3 Contact Information


Marie R. Coyea, Ph.D.
Universite Laval
Faculte de foresterie et geomatique
Pavillon Abitibi-Price 
Sainte-Foy, Quebec Canada
(418)656-2131
marie.coyea@sbf.ulaval.ca

3. Theory of Measurements

The gas exchange measurements were made with a closed portable photosynthetic 
system (LiCOR LI-6200). As described in the LI-6200 Primer Manual, it contains 
three major components: a leaf chamber, within that temperature and humidity 
measurements are made; the LI-6250, an infrared gas analyzer (IRGA) which 
measures CO2 concentration and flow rate; and a control console.  Air 
temperature, leaf temperature, and relative humidity are measured in the leaf 
chamber.  The pump in the LI-6250 circulates air from the chamber to the 
analyzer, where CO2 concentration is measured, and returns it to the chamber.  
The air flow through the LI-6250 can be diverted through soda lime to remove CO2 
for purposes of calibration.

The flow valve is used to force some fraction of the flow through a tube of 
desiccant, which dries the air.  This proportional control feature is used to 
help maintain a steady humidity in the chamber during a measurement.  The flow 
rate of the air going through the desiccant is measured by a flow meter.  

The IRGA can be used for absolute or differential measurement of CO2.  As used 
with the LI-6200, however, it is configured for absolute measurements.

The methodology for measuring leaf area is described in Appendix K of the 
Experiment Plan, Version 3.0.  Aspen foliage is expressed as hemisurface area 
leaf area, while conifer foliage is expressed as total surface area leaf area.

The optical image analysis system (Decagon AgVision System) is an image analysis 
system that works by first looking at an object through a video camera, then 
processing the image into discrete numerical information with a digitizer and 
microcomputer, and finally displaying the image or other information on a 
monitor for examination.

For the measurement of Y (please note that in the text below, "Y" is the Greek 
symbol psi that is generally used for water potential) response at high (less 
negative) Y, the cut end of the stem was connected to a water reservoir.  For 
lower (more negative) Y,  the branches were taken out of water and the cut 
surface of the stem was dried and sealed with silicone grease.  The branches 
were then exposed to light and permitted to transpire freely in an open space 
where the air was stirred continuously using an electric fan.  Sealing the cut 
surface of the branch allowed the branch to maintain a negative pressure inside 
the xylem while transpiration continued.  A pair of branches was chosen randomly 
at various times for gas exchange measurement at 20 C.  The transpiration rate 
of the branch being measured was kept very low by maintaining a high humidity in 
the cuvette (VPD < 0.8 kPa).  It took from 3 to 6 hours for branches to reach 
their minimum Y.  Immediately after the gas exchange measurement, the stem of 
the branch was cut and the water potential was measured with a pressure chamber 
(Model 610, PMS Instrument Inc., Corvallis, OR, USA).  By controlling the time 
interval between measurements, a range of water potentials was achieved for 
black spruce and jack pine during both Intensive Field Campaign (IFC)-2 and IFC-
3.

4. Equipment

4.1 Sensor/Instrument Description

LI-6200 portable gas exchange system (LI-COR), pressure chamber (PMS Instrument 
Co.), drying oven, optical image analysis system (Decagon Devices Inc., Pullman, 
WA), top loading weighing balance, IBM or compatible computer.

4.1.1 Collection Environment

Gas exchange and water potential measurements were measured by persons on the 
upper and lower levels of canopy access towers.  In the YJP stand, only 3 m 
ladders only were necessary. Leaf area measurements were determined in the lab.

4.1.2 Source/Platform

Gas exchange and water potential measurements were measured by persons on the 
upper and lower levels of canopy access towers.  In the YJP stand, only 3-m 
ladders were necessary. Leaf area measurements were determined in the lab.

4.1.3 Source/Platform Mission Objectives

The purpose of this study was threefold as outlined in the BOREAS Experiment 
Plan, Version 3.0, Appendix N, page N-34):

1) To describe the diurnal patterns of stomatal conductance, photosynthesis, and 
leaf water potential of the principal forest types present at the BOREAS NSA and 
to determine the precise nature of the environmental controls on these 
variables. 

2) To understand how these physiological properties and their environmental 
controls are influenced by canopy position and period of the growing season.  

3) To use these data for partial model validation with a model parameterized 
from laboratory data to be compared eventually to flux tower data from the NSA.

4.1.4 Key Variables

Diurnal water potential and net photosynthesis.

4.1.5 Principles of Operation

Gas exchange measurements were taken with a LI-COR 6200 system. Generally, a 
branch (bearing leaves) section was placed into the cuvette for three 20 second 
measurements.  The same branch section was measured periodically throughout the 
day (approximately once every hour).  At the end of the day, these branch 
sections were harvested and stored in a freezer until leaf area was determined.  

The volume displacement method (Appendix K of BOREAS Experiment Plan, version 
3.0) was used to measure leaf area of conifer needles.  The optical image 
analysis system was used to measure needle lengths and aspen projected leaf 
areas.

Water potential measurements were simultaneously taken with a pressure chamber 
on randomly selected branch sections at the same canopy level as the 
photosynthetic measurements. These samples were not kept for any further 
analyses.

4.1.6 Sensor/Instrument Measurement Geometry

Measurements were taken at two canopy levels: top and bottom.  The heights of 
these samples varied according to the location of the canopy access tower; 
however, they reflected the average canopy as described in Section 2.2.3.1 of 
the BOREAS Experiment Plan, Version 3.0.  Because the canopy access towers moved 
between IFC periods, the canopy levels were not always exactly the same.  For 
example, the measurements at the old aspen stand ranged from approximately 13-15 
m for the upper canopy and 9-11 m for the lower canopy.

4.1.7 Manufacturer of Sensor/Instrument

LI-6200 portable gas exchange system
LI-COR
P.O.Box 4425,
4421 Superior St., 
Lincoln, NE 68504
(800) 447-3576   

Pressure Chamber, Model 610
PMS Instrument Co.
480 SW Airport Avenue
Corvallis, OR 97333
503-752-7926

Leaf area measurement system/optical image analysis system (AgVision,
Monochrome system, root and leaf analysis)
Decagon Devices, Inc.
P.O. Box 835
Pullman, WA99163
(800) 755-2751


IBM DX2/486 Computer
IBM, Inc.

4.2 Calibration

The LI-COR LI-6200 was sent to the manufacturer for calibration and general 
maintenance in February 1994 before field work began (big mistake, see Section 
10.1).  The LI-6200 was examined daily for page parameters, operating 
parameters, and clock setting; quantum sensor calculation constant; CO2 analyzer 
calculation list; flow meter calculation list; relative humidity sensor 
calculation list; and analyzer reference. 

Each sensor was checked daily and periodically to make sure it was responding as 
expected: quantum sensor; air and leaf temperature match; IRGA temperature; flow 
meter; CO2 concentration; and relative humidity. The zero and span for the CO2 
analyzer were set daily. The flow meter was zeroed frequently. 

The LI-6250 CO2 gas analyzer was calibrated daily according to instrument 
specifications (CO2 levels), while system tests (e.g., leak tests, boundary 
layer resistance, soda lime test, and desiccant (k) test) were conducted 
periodically throughout each sampling day.  Approximately every half hour, the 
desiccant tube was shaken. 

Daily, the chambers were cleaned and the batteries recharged.  The foam pads in 
the chamber were changed after frequent usage and any noticeable damage.

The optical image analysis system was calibrated according to instrument 
specifications each time the system was opened or after it was left for a period 
of time.  A fine ruler and flat disks of known area were used in the 
calibration.  

The pressure chamber was inspected at the manufacturer's facility prior to field 
use. Safety checks were conducted from time to time throughout the sampling 
period.

4.2.1 Specifications

The weighing balance was accurate to within 0.0001 g.
The leaf area system was accurate to within 1%.
The gas exchange system was accurate to 1 ppm CO2.

The shape factor used for black spruce was 4, in accordance with the BOREAS 
Experiment Plan, Appendix K, Version 3.0. Based on observations of two cross-
sections of two needles per fascicle for five fascicles for six jack pine trees 
from Thompson, Manitoba, an average shape factor of 4.59 (+/- 0.07) was 
calculated.

4.2.1.1 Tolerance

The acceptable range for net photosynthetic measurements is not available at
this revision.

4.2.2 Frequency of Calibration

The LI-COR LI-6200 was sent to the manufacturer for calibration and general 
maintenance in February 1994 before field work began (big mistake, see Section 
10.1).  The LI-6200 was examined daily for page parameters, operating 
parameters, and clock setting; quantum sensor calculation constant; CO2 analyzer 
calculation list; flow meter calculation list; relative humidity sensor 
calculation list; and analyzer reference. 

Each sensor was checked daily and periodically to make sure it was responding as 
expected: quantum sensor; air and leaf temperature match; IRGA temperature; flow 
meter; CO2 concentration; and relative humidity. The zero and SPAN for the CO2 
analyzer were set daily. The flow meter was zeroed frequently. 

The LI-6250 CO2 gas analyzer was calibrated daily according to instrument 
specifications (CO2 levels), while system tests (e.g., leak tests, boundary 
layer resistance, soda lime test, and desiccant (k) test) were conducted 
periodically throughout each sampling day.  Approximately every half hour, the 
desiccant tube was shaken. 

Daily, the chambers were cleaned and the batteries recharged.  The foam pads in 
the chamber were changed after frequent usage and any noticeable damage.

The optical image analysis system was calibrated according to instrument 
specifications each time the system was opened or after it was left for a period 
of time.  A fine ruler and flat disks of known area were used in the 
calibration.  

The pressure chamber was inspected at the manufacturer's facility prior to field 
use. Safety checks were conducted from time to time throughout the sampling 
period.


4.2.3 Other Calibration Information

During IFC-1, the LI-6200 system had problems caused by the manufacturer's 
calibration.  For the days when this equipment problem  occurred, the data could 
not be treated and thus will not be stored in the BOREAS Information System 
(BORIS).  Furthermore, the radio handsets that were distributed to the field 
groups caused some failure in instrument functioning.  Either the instrument 
completely shut down or the periodic calibrations detected the influence of the 
handsets. These data have been cleaned and removed from the data set available 
in BORIS.

5. Data Acquisition Methods

Gas exchange and water potential measurements took place in five stands during 
daylight hours.  Prior to each measurement period, instruments were calibrated 
and placed onsite (for example, on canopy access towers) for measurement.  Five 
branches from randomly selected trees at a given canopy level were identified 
and prepared by exposing only a desirable amount of foliage for gas exchange 
measurement. Net photosynthesis was measured on these branches with a LI-COR LI-
6200 system. Ambient conditions were also obtained once or twice within the 
measurement period of the five samples. 

Once a canopy level was completed, another was started, which normally was 
within a half hour. Several cycles of measurement (upper and lower canopy) could 
be completed during a day.  During the first IFC only, samples were harvested 
after four to five cycles and another five were selected. This was done to 
ensure that the measurement technique did not affect the sample by inducing high 
respiration rates from damaged tissue, for example.

A branch (bearing leaves) section was placed into the cuvette for three 20-
second measurements. This period varied in the first IFC, when investigators 
were trying to find an ideal measurement period for the species being measured. 
Three 30-second measurements, or three 60-second intervals, were found to be too 
long. Two 20- or 30-second intervals did not always provide enough data to 
determine whether data errors existed. The same branch section was measured 
periodically throughout the  day (approximately once every hour). At the end of 
the day, these branch sections were harvested and stored in a freezer until leaf 
area was determined.  

The projected leaf areas of fresh aspen leaves that were harvested following the 
gas exchange measurements were measured using an optical image analysis system. 
Projected leaf area is essentially equivalent to half the area of the surface of 
the leaf (HASL) for flat leaves. Leaf area of each fresh conifer sample was 
measured using the volume displacement method as described in Appendix K of the 
BOREAS Experiment Plan (Version 3.0). Because precision work was required, the 
needles were removed from the shoot and the volume of the woody portion of the 
shoot was measured by submerging it in the liquid-filled container on the 
balance.  The needle volume was the difference between the total volume and the 
woody volume.  The length of all needles in the sample and the shoot silhouette 
were measured using the optical image analysis system.  The shape factors for 
black spruce and jack pine respectively were 4.00 and 4.59.

The silhouette area of conifer samples was measured by age class.  (In the first 
IFC, however, there was only one age class.)  A conifer shoot was first 
snipped/clipped into two age classes.  These two age classes included (1) 1994 
needles and (2) anything produced in 1993 and earlier.  Each shoot section was 
then randomly thrown under the camera lens and a silhouette measurement was 
taken.  These samples were then processed under the normal procedures for 
measuring leaf area (volume displacement).


6. Observations

6.1 Data Notes

6.2 Field Notes

During IFC-1 only, canopy gas exchange measurements were made only in the upper 
canopy with the exception of 27-May in the YJP stand.  On this particular day, 
gas exchange measurements were made on three branches per tree, for five trees 
for three canopy levels. (The data set will reflect this difference in 
numbering.) Water potential measurements were made on 1-Jun and for subsequent 
days. Identification errors have been corrected in the data set and are too 
detailed to 
list here.

7. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

The data were collected from five principal sites in the NSA of Manitoba.  The 
NSA is approximately 100 km wide by 80 km and is located 735 km north of 
Winnipeg.  The principal sites in this study were:

NSA-YJP flux tower site:
Lat/Long: 55.89575 N, 98.28706 W 
UTM Zone 14, N:6194706.9 E:544583.9 

NSA-OJP flux tower site:
Lat/Long: 55.842 N, 98.62396 W  
UTM Zone 14, N:6198176.3 E:523496.2 

NSA-OA canopy access tower site (auxiliary site number T2Q6A, BOREAS Experiment 
Plan, Version 3.0):
Lat/Long: 55.88691 N, 98.67479 W
UTM Zone 14, N: 6193540.7 E: 520342

NSA-OBS flux tower site:
Lat/Long: 55.88007 N, 98.48139 W
UTM Zone 14, N:6192853.4 E:532444.5

NSA-UBS canopy access tower site (auxiliary site number T6R5S, BOREAS Experiment 
Plan, Version 3.0):  
Lat/Long: 55.90802 N, 98.51865 W
UTM Zone 14, N: 6195947 E:530092

Measurements were taken on the canopy access towers or, in the case of the YJP 
site, within 1 km of the flux tower.

7.1.2 Spatial Coverage Map

Not available.

7.1.3 Spatial Resolution

The data represent point source 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

Data acquisition took place during the three IFCs, which lasted from 24-May-1994 
to 19-Sept-1994.

7.2.2 Temporal Coverage Map

Not available.

7.2.3 Temporal Resolution

During the first IFC, because of problems with the LI-6200, usable data were 
obtained only for four sampling days: YJP, 17-May; OJP, 30-May, and 01-June; and 
OBS, 05-Jun.

During the second IFC, usable data were obtained for seven sampling days: YJP, 
August 1; OJP 27-Jul, 09-Aug; OASP, 29-Jul, 08-Aug; OBS, 05-Aug; and UBS, 03-
Aug.

During the third IFC, usable data were obtained for eight sampling days: YJP, 
01- and 10-Sept; OJP, 31-Aug, 09-Sep; OASP, 03-Sept and 16-Sept; OBS, 
07-Sept; and UBS, 17-Sep.


7.3 Data Characteristics                                                        
                                                                                
Data characteristics are defined in the companion data file (te09gxda.def).
                                                                     
7.4 Sample Data Record

Sample data format shown in the companion data definition file (te09gxda.def).

8. Data Organization

8.1 Data Granularity

All of the In Situ Diurnal Gas Exchange of NSA Boreal Forest Stands Data are 
contained in one dataset.

8.2 Data Format(s)

The data files contain numerical and character fields of varying length 
separated by commas. The character fields are enclosed with  a single apostrophe 
marks. There are no spaces between the fields.  Sample data records are shown in 
the companion data definition files (te09gxda.def).

9. Data Manipulations

9.1 Formulae

During the data processing, the following formulae were used: 

a) water use efficiency (WUE)=(photosynthesis (mol m-2 s-1) /transpiration(mmol 
m-2 s-1))

b) mesophyll conductance (GM)=( (photosynthesis (mol m-2 s-1) /Intercellular 
CO2 concentration (ppm)) x 1000) 

(Fites and Teskey, 1988. Can. J. For. Res. 18:150-157).

c) Ci/Ca: CINT: Intercellular CO2 concentration (ppm) / CO2 concentration (ppm))

9.1.1 Derivation Techniques and Algorithms

None at this time.

9.2 Data Processing Sequence

9.2.1 Processing Steps

Data were stored in the LI-6200 system during the measurement day.  Data were 
then downloaded/transferred from the system to an IBM or IBM compatible 
computer.

When the true leaf areas for each sample were available, these values were 
entered into the LICOR programming software, and all gas exchange parameters 
subsequently were recomputed.

Raw data for each day of data were printed and examined for anomalies in each 
line of data.  Subsequently any data corresponding to each line of data that 
showed an anomaly were removed.  For example, a branch was normally placed in 
the cuvette for three repetitions of 20 seconds. If in one (or more) of these 
repetitions, a parameter output was more than 25% out of range, then the entire 
line of data was removed, leaving only the data corresponding to the 'clean' 
repetitions.

Data were recomputed using the LI-COR software if any other errors in default 
parameters were detected.  For example, on occasion, the ratio of the stomatal 
conductance of one side of the leaf to the other (STMRAT) was erroneously 
entered in the field. 

Using Excel (Version 5.0 for IBM), a program was written to process each cleaned 
data set.  This program did the following:

1) Calculated new parameters that were not part of the LI-COR software system.  
These parameters included water use efficiency, mesophyll conductance, and Ci:Ca 
ratios. 
2) Permitted the user to average the data depending on whether the data had been 
recomputed or not.
3) Permitted the user to average the data depending on whether there were two or 
three repetitions of data, taking into account missing data.
4) Formatted the data into column format. 

Once the data were in a cleaned, column format, water potential values for each 
time period were entered into the data set.  Data in imperial units were 
converted to standard metric units.

9.2.2 Processing Changes

See Section 9.2.1.

9.3 Calculations

During the data processing, the following formulae were used: 

a) water use efficiency (WUE)=(photosynthesis (mol m-2 s-1) /transpiration(mol 
m-2 s-1))

b) mesophyll conductance (GM)=( (photosynthesis (mol m-2 s-1) /Intercellular 
CO2 concentration (ppm)) x 1000 )

(Fites and Teskey, 1988. Can. J. For. Res. 18:150-157).

c) Ci/Ca: CINT: Intercellular CO2 concentration (ppm) / CO2 concentration (ppm)


9.3.1 Special Corrections/Adjustments

Raw data for each day of data were printed and examined for anomalies in each 
line of data.  Subsequently, any data corresponding to each line of data that 
showed an anomaly were removed.  For example, a branch was normally placed in 
the cuvette for three repetitions of 20 seconds. If in one (or more) of these 
repetitions, a parameter output was more than 25% out of range, then the entire 
line of data was removed, leaving only the data corresponding to the 'clean' 
repetitions.

Data were recomputed using the LI-COR software if any other errors in default 
parameters were detected.  For example, on occasion, the ratio of the stomatal 
conductance of one side of the leaf to the other (STMRAT) was erroneously 
entered in the field. 

Using the software Excel (Version 5.0 for IBM), a program was written to process 
each cleaned data set.  This program did the following:

1) Calculated new parameters that were not part of the LI-COR software system.  
These parameters included water use efficiency, mesophyll conductance, and Ci:Ca 
ratios. 
2) Permitted the user to average the data depending on whether the data had been 
recomputed or not.
3) Permitted the user to average the data depending on whether there were two or 
three repetitions of data, taking into account missing data.
4) Formatted the data into column format. 

Once the data were in a cleaned, column format, water potential values for each 
time period were entered into the data set.  Data in imperial units were 
converted to standard metric units.

9.3.2 Calculated Variables

water use efficiency (WUE)
mesophyll conductance (GM)
intercellular CO2 concentration(ppm)

9.4 Graphs and Plots

None submitted.

10. Errors

10.1 Sources of Error

During IFC-1, the LI-6200 system had problems caused by the manufacturer's 
calibration. For days when this equipment problem  occurred, the data could not 
be treated and thus will not be stored in BORIS.  Furthermore, the radio 
handsets that were distributed to the field groups caused some failure in 
instrument functioning.  Either the instrument completely shut down or the 
periodic calibrations detected the handset influence. These data have been 
cleaned and removed from the data set available in BORIS.

All erroneous default parameters were adjusted.

Anomalies in each line of data were removed.  For example, a branch was normally 
placed in the cuvette for three repetitions of 20 seconds.  If in one (or more) 
of these repetitions, a parameter output was more than 25% out of range, then 
the entire line of data was removed, leaving only the data corresponding to the 
'clean' repetitions.  Most often these anomalies could not be explained.  
However, a sudden burst in light during the measurement or a poor electrical 
signal could cause these kinds of errors.   These out-of-range errors were 
detected and removed.

See Section 9.2.1. for additional details.

10.2 Quality Assessment


10.2.1 Data Validation by Source

All known errors were removed.

10.2.2 Confidence Level/Accuracy Judgment

All known errors were removed, yielding a high degree of confidence in this data 
set.

10.2.3 Measurement Error for Parameters

No measurement errors are known at this time

10.2.4 Additional Quality Assessments

Data were compared to results observed in the laboratory, and results are within 
a 
realistic range.

10.2.5 Data Verification by Data Center

Data was examined for general consistency and clarity.

11. Notes

11.1 Limitations of the Data

None given.

11.2 Known Problems with the Data

All known problems have been removed; see Section 10.1.

11.3 Usage Guidance

Use data columns as presented.

11.4 Other Relevant Information

Not available at this time.

12. Application of the Data Set

These data can be used to characterize the diurnal water potential curves for 
these sites to obtain an indication to what  extent soil moisture supply to 
leaves might be limiting photosynthesis.

13. Future Modifications and Plans

This is the final version of data.

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)
beth@ltpmail.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.  Discussions with either Marie Coyea or Hank Margolis before using this 
data are essential.

15.4 Data Center Status/Plans

The TE-09 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 ASCII files.

17. References

Fites, J.A. and R. O. Teskey.  1988. CO2 and water vapour exchange of Pinus in 
relation to stomatal behavior: test of an optimization hypothesis. Can. J. For. 
Res. 18:150-157

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Decagon Devices Inc. 1990 AgVision monochrochrom system, root and leaf analysis, 
operators manual. Pullman, WA.

LI-COR,Inc. 1990. LI-COR 6200 Condensed Reference.  Software Revision 2.00 
(August 1990).  Lincoln, NE.

LI-COR, Inc. 1990. The LI-COR 6200 Primer: An introduction to operating the LI-
6200 portable photosynthesis system. (May 1990) Lincoln, NE.

LI-COR, Inc. 1990. LI-COR 6200 Technical reference. (March 1990). Lincoln, NE.

LI-COR, Inc. 1993. LI-COR 6200 software.  Lincoln, NE.

17.2 Journal Articles and Study Reports

Coyea, M.R., Q-L. Dang,  H. Margolis, M. Sy, and G. J. Collatz.  1996.  Canopy 
profiles of PAR, nitrogen, and photosynthetic capacity:implications for scaling 
from leaf to canopy. North American Forest Biology Workshop.  June 16-20 1996.  
Poster presented.

Dang, Q-L., H. Margolis, M.R. Coyea, M. Sy, G.J. Collatz and De Yue.  1995.  
Environmental controls on photosynthesis and stomatal conductance of boreal 
forest tree species.  Ecological Society of America.  July 31-August 4, 1995.  
Snowbird, UT.

Dang, Q-L., H. Margolis, M. Sy, M.R. Coyea, and G. J. Collatz. 1996.  Profiles 
of photosynthetically active radiation, nitrogen, and photosynthetic capacity in 
the boreal forest:  implications for scaling from leaf to canopy.  Ecological 
Society of America.  August 10-14, 1996.  Providence RI.  

Dang, Q-L., H. Margolis, M. Sy, M.R. Coyea, and G.J. Collatz. 1996.  Water 
potential and vapor pressure difference as environmental controls on branch-
level gas exchange of boreal tree species in northern Manitoba.  North American 
Forest Biology Workshop.  June 16-20, 1996. 

Dang, Q.L., H. Margolis, M.R. Coyea, M. Sy, and G. J. Collatz,.  1996.  
Regulation of branch-level gas exchange of boreal trees: role of shoot water 
potential and vapor pressure difference.  Tree Phys.  In press.

Dang, Q.L., H. Margolis, M. Sy, M.R. Coyea, G.J. Collatz, and C. L. Walthall.  
1996.  Profiles of PAR, nitrogen, and photosynthetic capacity in the boreal 
forest:  Implications for scaling from leaf to canopy.  J. of Geophys. Res. In 
press.

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., and F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in 
press).

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. 

17.3 Archive/DBMS Usage Documentation

None.

18. Glossary of Terms

None.

19. List of Acronyms 
    BOREAS  - BOReal Ecosystem-Atmosphere Study
    BORIS   - BOREAS Information System
    DAAC    - Distributed Active Archive Center
    EOS     - Earth Observing System
    EOSDIS  - EOS Data and Information System
    FPAR    - Fraction of PAR
    GSFC    - Goddard Space Flight Center
    HASL    - Half the Area of the Surface of the Leaf
    IFC     - Intensive Field Campaign
    IRGA    - Infrared Gas Analyzer
    NASA    - National Aeronautics and Space Administration
    NSA     - Northern Study Area
    OA      - Old Aspen 
    OBS     - Old Black Spruce
    OJP     - Old Jack Pine 
    PANP    - Prince Albert National Park
    PAR     - Photosynthetically Active Radiation
    PI      - Principal Investigator
    Ps      - Photosynthesis
    ORNL    - Oak Ridge National Laboratory
    UBS     - Upland Black Spruce 
    URL     - Uniform Resource Locator
    VPD     - Vapor Pressure Deficit
    YA      - Young Aspen
    YJP     - Young Jack Pine 


20. Document Information

20.1 Document Revision Date 

Written: 27-Feb-1997
Last Updated:  08-May-1998

20.2 Document Review Date(s) 
     BORIS Review: 26-Feb-1998
     Science Review:06-Feb-1998 

20.3 Document ID 

20.4 Citation 

The diurnal gas exchange and water potential measurements were collected for 
BOREAS by the TE-09 research team from Universite Laval, Quebec, Canada, under 
the direction of H. Margolis.  The dedicated efforts of Marie R. Coyea, Mikailou 
Sy, Raynald Paquin, Simon Arbour, Munyonge Abwe Wa Masabo, and Tshinkenke Vinlha 
in collecting and preparing these data is particularly appreciated.

20.5 Document Curator 

20.6 Document URL 

WATER POTENTIAL
PHOTOSYNTHETIC RATE
STOMATAL CONDUCT H20
STOMATAL CONDUCT CO2
INTERCELLULAR CO2 CONCENTRATION
TRANSPIRATION RATE
WATER USE EFFICIENCY
MESOPHYL CONDUCTANCE
INTERCELLULAR CO2 RATIO
PPFD
CO2 CONCENTRATION
LEAF AREA
LEAF BOUND LAYER CONDUCTANCE
STOMATAL CONDUCTANCE


TE09_Gas_Exchange
Page 18 of 1
05/26/98