BOREAS TF-09 SSA-OBS Branch Level Flux Data

Summary

The BOREAS TF-09 team collected data which describe carbon dioxide and
water vapor fluxes from foliage at the BOREAS SSA-OBS site from 07-April
through 23-November-1996. The data are available in tabular ASCII files.

Table of Contents

1\. Data Set/Model 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/Model

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-09 SSA-OBS Branch Level Flux Data

1.2 Data Set Introduction

A system of large cuvettes was used to measure whole branch CO2 and H2O
vapor exchange of four black spruce (Picea mariana \[Mill\] BSP)
branches at the BOReal Ecosystem-Atmosphere Study (BOREAS) Southern
Study Area (SSA) Old Black Spruce (OBS) site.

1.3 Objective/Purpose

The objective of this study was to measure and model the CO2 exchanges
of boreal black spruce forest branches over the course of an entire
growing season. These measurements will be used to parameterise models
and to assist scaling up procedures from leaf level to stand level (eddy
covariance) measurements.

1.4 Summary of Parameters and Variables

Measurements include CO2 and H2O fluxes, photosynthetic photon flux
density (PPFD), air and leaf temperatures, relative humidity, air
humidity deficit, and CO2 concentration.

1.5 Discussion

The branch bags consisted of two 5-mm-thick acrylic end pieces, oval in
shape (600-mm major axis, 300 mm minor axis, 0.14-m2 area), separated by
five thin (5 mm diameter) stainless steel rods. One end was made such
that it could slide up or down the rods in order to adjust the bag
length to suit the individual branch. An ovaloid shape was chosen to
minimize dead volume within the bag, to minimize the bag\'s surface area
to volume ratio (minimizing any adsorption/desorption effects), to
minimize attenuation of incoming light, and for aesthetic reasons. The
bag itself was effected by covering the structure with polypropylene
film (ICI Propafilm, 34-mm thickness, ICI PLC, London) and sealing along
the edge of the end piece with silicone sealant. The bottom of the bag
was left unsealed to allow placement of the bag upon the branch;
afterward, it and the branch entry point were sealed in a similar
fashion. A 12-volt electric fan (RS 583-050, RS Components Ltd.,
Northants) was mounted at the trunk end of each bag, and blew air at a
high flow rate (40 dm3 s-1, approximately 18 to 26 air changes min-1)
through the bag via large shrouded inlet and outlet ports. When a gas
exchange measurement was to be made, the ventilation fan was switched
off, thin flap valves dropped over the inlet and outlet and were shut
tight with small electromagnets, and an internal circulating fan was
switched on. Air was circulated (5 dm3 min-1) at all times between all
bags and the box containing the infrared gas analyzer (IRGA) and control
system through loops of tubing (5-mm i.d. Dekabon, Furon, Gembioux,
Belgium), and at measurement time a small amount of air (0.2 dm3 min-1)
was diverted from the appropriate loop to the IRGA (LI-6262, LI-COR
Inc., Lincoln, NE) operating in absolute mode. Within each bag, relative
humidity and air temperature were measured (Vaisala HMB 30A, Vaisala
(UK) Ltd., Cambridge), as was leaf temperature (thin Cu-Con thermocouple
referenced to the air temperature sensor) and, for a period, bag
internal vs. external temperature (Cu-Con thermocouple). Light incident
upon each branch was measured with a Macam light sensor (Macam SD101QV,
Macam, Livingstone) mounted directly onto the branch, midway along its
length. Sensor outputs were recorded through a Campbell AM416
multiplexer to a Campbell CR21X data logger (Campbell Scientific Ltd.,
Shepshed, Leics.), which also initiated the measurement sequence.

Each bag was closed for 5 minutes in turn, during which time the sensors
were read every 20 seconds; thus, each bag was measured every 20
minutes. Gas exchange was calculated from the slope of the regression of
gas concentration upon time (excluding the readings from the initial 40
s for CO2 and the initial 80 s for H2O vapor in order to ensure that the
IRGA was entirely flushed of the previous sample) and the volume of the
system (106.3, 134.3, 91.9, and 106.3 dm3 for bags 1 to 4,
respectively). The air sample bleed to the IRGA during the measurement
period was negligible (\~1 dm3) compared to the bag volume and was
ignored in calculations. All bags were leak tested by shading the branch
to its light compensation point, blowing into the bag to create a high
internal/external concentration differential, closing the inlet and
outlet ports, and monitoring bag concentration over a period of time.

1.6 Related Data Sets

BOREAS TF-09 SSA-OBS Tower Flux, Meteorological, and Soil Temperature
Data

BOREAS TE-11 SSA-OJP Branch Level Flux Data

BOREAS TE-12 Leaf Photosynthesis Data

BOREAS TE-10 Leaf Photosynthesis Data

2\. Investigator(s)

2.1 Investigator(s) Name and Title

Mr. Mark B. Rayment & Prof. Paul G. Jarvis

Institute of Ecology and Resource Management

University of Edinburgh

UK

2.2 Title of Investigation

The CO2 Exchanges of Boreal Black Spruce Forest

2.3 Contact Information

Contact 1

\-\-\-\-\-\-\-\--

Mr. Mark B. Rayment

Institute of Ecology and Resource Management

University of Edinburgh

Edinburgh

UK

+131 650 5423

+131 662 0478 (fax)

M.Rayment@ed.ac.uk

Contact 2

\-\-\-\-\-\-\-\-\-\-\-\--

K. Fred Huemmrich

University of Maryland

NASA GSFC

Greenbelt, MD

\(301\) 286-4862

\(301\) 286-0239 (fax)

Karl.Huemmrich@gsfc.nasa.gov

3\. Theory of Measurements

The net carbon uptake of a tree depends on the assimilation of carbon
dioxide by photosynthesis in the leaves and the carbon dioxide emissions
resulting from respiratory processes in the leaves and woody tissues of
the tree. Transpiration of water occurs mainly from the foliage.
Enclosures surrounding branches remain open for the majority of the time
and are periodically closed, at which time the rate of change of gas
concentration allows calculation of an integrated measure of the net
exchange of gases between the branch and the atmosphere.

4\. Equipment

4.1 Sensor/Instrument Description

4.1.1 Collection Environment

Measurements were collected from early April through late November;
temperatures ranged from below freezing to over 30 °C during that
period.

4.1.2 Source/Platform

The branch bags surrounded individual spruce branches. The bags were
supported in position by elastic ropes attached to the trunk above the
bag and, where necessary, to a support projecting from the canopy access
tower. This arrangement allowed the bags to move freely as the trees and
branches moved with the wind. Each of the bags was positioned on a
south-facing branch to minimize shading by the tower. The bags could be
reached from the canopy access tower, made of 5- by 9-foot scaffolding.

Instruments:

Gas concentration: IRGA LI-6262 (LI-COR Inc., Lincoln, NE) operating in
absolute mode.

Relative humidity and air temperature: Vaisala HMB 30A (Vaisala (UK)
Ltd., Cambridge).

Leaf temperature: thin Cu-Con thermocouple referenced to the air
temperature sensor.

Incident PPFD: Macam SD101QV light sensor mounted directly onto the
branch, midway along its length.

Logger: Campbell AM416 multiplexer and Campbell CR21X data logger.

Tubing: 5-mm i.d. Dekabon.

4.1.3 Source/Platform Mission Objectives

The objective was to measure branch scale CO2 and water vapor fluxes and
related environmental variables in black spruce at the southern edge of
the boreal forest.

4.1.4 Key Variables

CO2 and water vapor fluxes.

Supporting meteorological variables: PPFD, air temperature, leaf
temperature, CO2, water vapor concentration.

4.1.5 Principles of Operation

The LI-COR LI-6262 IRGA is a closed-path instrument with reference and
sample cells with an infrared source at one end and a detector at the
other. Different gases absorb infrared of different frequencies, and
filters are used to select a narrow band that corresponds to an
absorption band of the gas of interest. The LI-6262 measures CO2 and H2O
concentrations. A gas of known concentration is passed through a
reference cell, and the gas whose concentration is to be measured is
passed through the sample cell. The amount of infrared reaching the
detector in each cell is a function of the gas concentration in the
cell. The difference in voltage produced by the detectors of the
reference and sample cells is then a function of the difference in
concentration of the gas in the cells. Other sensors were common
meteorological sensors used in a standard fashion. For principles of
operations of these sensors, please see a relevant textbook; e.g.,
Pearcy et al. (1991).

4.1.6 Sensor/Instrument Measurement Geometry

Two branch bags were installed on each of two trees at the SSA-OBS site
in early April 1996. Two bags were positioned in the upper canopy (at
7.85 m above the ground for branch number 1 and 8.25 m for branch number
3) and two in the lower canopy (at 5.22 m for branch number 2 and 5.48m
for branch number 4); the trees\' DBH were 10 cm and 9 cm. The bags were
supported in position by elastic ropes attached to the trunk above the
bag and, where necessary, to a support projecting from the canopy access
tower. This arrangement allowed the bags to move freely as the trees and
branches moved with the wind. Each of the bags was positioned on a
south-facing branch to minimize shading by the tower. Humidity, air and
leaf temperatures, and PPFD were measured within the bag, close to or in
contact with the leaves. Gas concentration was measured on a sample of
air circulated between the bag and the IRGA. The IRGA was positioned in
an insulated box mounted on the canopy access tower.

4.1.7 Manufacturer of Instrument

Licor LI-6262

P.O. Box 4425/4421,

Superior Street,

Lincoln, NE 68504

USA

Vaisala HMB 30A

Vaisala (UK) Ltd.,

Cambridge

UK

Macam SD101QV light sensor

Macam

Livingstone

UK

Campbell AM416 multiplexer and Campbell CR21X data logger

Campbell Scientific

P. O. Box 551,

Logan, UT 84321

USA

Dekabon tubing

J. P. Deane & Co. Ltd.,

91, Ormonde Crescent,

Glasgow G44 3SW

UK

4.2 Calibration

4.2.1 Specifications

LI-6262:

The output linearization of this instrument was calibrated by the
manufacturer and was last performed in July 1993. The field calibration
fixes the lower and upper ends of the linearization function and is
carried out by passing CO2 and water vapor free air through the
reference cell (the instrument is used in the absolute mode) and setting
the CO2 and water vapor channels to zero. The upper point is set by
passing dry air of known CO2 or of known water vapor concentration
through the sample cell and adjusting the appropriate channel to read
the correct value. CO2 standard gases were cross-referenced to the
BOREAS primary standards, and a LI-COR LI-610 dewpoint generator was
used to produce air of known water vapor density.

The Vaisala temperature and humidity probes either were bought new or
were returned to the manufacturer for calibration immediately prior to
installation.

The Macam PPFD sensors were purchased new immediately prior to
installation, and the manufacture\'s calibration factors were used.

All bags were leak tested by shading the branch to its light
compensation point, blowing into the bag to create a high
internal/external concentration differential, closing the inlet and
outlet ports and monitoring bag concentration over a period of time.

The LI-6262 was usually calibrated every 4 to 7 days. Typical CO2 drift
was 1-ppm drift in span and offset. Typical drift for the water vapor
was 0.1 kPa in span and offset.

4.2.1.1 Tolerance

None.

4.2.2 Frequency of Calibrations

The LI-6262 was usually calibrated every 4 to 7 days.

4.2.3. Other Calibration Information

None.

5\. Data Acquisition Methods

When a gas exchange measurement was to be made, the ventilation fan was
switched off, thin flap valves dropped over the inlet and outlet and
were shut tight with small electromagnets, and an internal circulating
fan was switched on. Air was circulated (5 dm3 min-1) at all times
between all bags and the box containing the IRGA and control system
through loops of tubing, and at measurement time a small amount of air
(0.2 dm3 min-1) was diverted from the appropriate loop to the IRGA
operating in absolute mode. Within each bag, relative humidity and air
temperature were measured, as was leaf temperature and, for a period,
bag internal vs. external temperature. Light incident upon each branch
was measured with a Macam light sensor mounted directly onto the branch,
midway along its length.

Each bag was closed for 5 minutes in turn, during which time the sensors
were read every 20 seconds; thus, each bag was measured every 20
minutes. Gas exchange was calculated from the slope of the regression of
gas concentration upon time (excluding the readings from the initial 40
s for CO2 and the initial 80 s for H2O vapor in order to ensure that the
IRGA was entirely flushed of the previous sample) and the volume of the
system (106.3, 134.3, 91.9, and 106.3 dm3 for bags 1 to 4,
respectively). The air sample bleed to the IRGA during the measurement
period was negligible (\~1 dm3) compared to the bag volume and was
ignored in calculations.

A Campbell Scientific 21x data logger was used to log the data together

with a Campbell AM416 multiplexer. The raw signal from each sensor was

converted into the appropriate units in the data logger program. The
data logger also initiated the measurement sequence.

6\. Observations

6.1 Data Notes

Values given are on a PROJECTED leaf area basis; that is, values should
be adjusted by a shape factor to express rates on a total surface or
hemisurface area basis. For black spruce, hemisurface area was last
reported to be 1.27 x projected area; i.e., these rates would be divided
by 1.27 to given rates on a hemisurface area basis.

6.2 Field Notes

None given.

7\. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

All data were collected at the BOREAS SSA-OBS site. North American Datum
1983 (NAD83) coordinates for this site are latitude 53.98717° N,
longitude 105.11779° W, and elevation of 628.94 m.

Branches had total projected needle areas of 3115, 2014, 1657, and 2342
cm2, for chambers one through 4, respectively.

7.1.2 Spatial Coverage Map

None.

7.1.3 Spatial Resolution

The values are point measurements from trees near the locations given in
Section 7.1.1.

7.1.4 Projection

None.

7.1.5 Grid Description

None.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

The data were collected from 06-April to 22-November-1996. Data were
collected continuously with gaps between 18- and 26-June and 03- and
07-July.

7.2.2 Temporal Coverage Map

All data were collected at the BOREAS SSA-OBS site.

7.2.3 Temporal Resolution

Each observation took 5 minutes to complete data collection cycled
through each of the four bags so that observations of any given bag
occur every 20 minutes.

7.3 Data Characteristics

Data characteristics are defined in the companion data definition file
(tf9brflx.def).

7.4 Sample Data Record

Sample data format shown in the companion data definition file
(tf9brflx.def).

8\. Data Organization

8.1 Data Granularity

All of the SSA-OBS Branch Level Flux Data are contained in one dataset.

8.2 Data Format

The data files contain 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 (tf9brflx.def).

9\. Data Manipulations

9.1 Formulae

None.

9.1.1 Derivation Techniques and Algorithms

None.

9.2 Data Processing Sequence

A linear fit was made between the gas concentrations and time; data were
rejected if the sum of the squares of the residuals was less than 0.9
and the calculated flux was non zero.

9.2.1 Processing Steps

BORIS staff processed these data by:

1\) Reviewing the initial data files and loading them online for BOREAS
team access.

2\) Designing relational data base tables to inventory and store the
data.

3\) Loading the data into the relational data base tables.

4\) Working with the team to document the data set.

5\) Extracting the data into logical files.

9.2.2 Processing Changes

None.

9.3 Calculations

Flux calculations:

flux = (concentration change \* molar volume)/(time interval \* leaf
area)

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

Major sources of error include sensor drift, measurement of branch bag
volume, and measurement of leaf area.

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 to check for spikes, values that are four standard
deviations from the mean, long periods of constant values, and missing
data.

11 Notes

11.1 Limitations of the Data

Potential users of these data should be aware of the limitations of gas
exchange as a means of investigating photosynthesis and of the
implications of these measurements having been made on entire, enclosed
branches.

11.2 Known Problems with the Data

All known bad data have been removed from the files.

11.3 Usage Guidance

Potential users of these data should be aware of the limitations of gas
exchange as a means of investigating photosynthesis and of the
implications of these measurements having been made on entire, enclosed
branches. They should also be aware that these data have been submitted
to BORIS out of courtesy rather than contractual obligation and should
therefore seek the permission of the investigators before publishing
analyses derived from them. These data remain the property of the
University of Edinburgh and of the UK Natural Environment Research
Council.

11.4 Other Relevant Information

None.

12\. Application of the Data Set

This data set is useful for the examination of effects of environmental
variables on photosynthesis and transpiration at the scale of individual
branches.

13\. Future Modifications and Plans

Although these data represent the most recent data set, believed to be
error

free, some data might, in the future, be found to be in error.

14\. Software

14.1 Software Description

Logger program written with Campbell PC208. Flux and humidity-based
calculations and initial screening of the data were carried out with a
program written in Microsoft Visual Basic. Final data screening was
carried out in SAS.

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

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

The data are available as tabular American Standard Code for Information
Interchange (ASCII) text files.

17\. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

None

17.2 Journal Articles and Study Reports

Pearcy, R.W., J. Ehleringer, H. A. Mooney, and P. W. Rundel. 1991. Plant
Physiological Ecology: Field methods and instrumentation. Chapman and
Hall, London and New York.

Rayment, M.B. 1998. Ph.D. Thesis. University of Edinburgh.

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., 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

DBH - Diameter at Breast Height

EOS - Earth Observing System

EOSDIS - EOS Data and Information System

GSFC - Goddard Space Flight Center

IRGA - Infra-Red Gas Analyzer

NASA - National Aeronautics and Space Administration

NSA - Northern Study Area

ORNL - Oak Ridge National Laboratory

OBS - Old Black Spruce

PANP - Prince Albert National Park

PPFD - Photosynthetic Photon Flux Density

SSA - Southern Study Area

TF - Tower Flux

URL - Uniform Resource Locator

20\. Document Information

20.1 Document Revision Date

Written: 25-Jun-1997

Revised: 06-Oct-1998

20.2 Document Review Date(s)

BORIS Review: 23-Jul-1998

Science Review:

20.3 Document ID

20.4 Citation

M.B.Rayment and P.G.Jarvis, Institute of Ecology and Resource
Management,

Edinburgh University.

Users of these data should be aware that these data have been submitted
to BORIS out of courtesy rather than contractual obligation and should
therefore seek the permission of the investigators before publishing
analyses derived from them. These data remain the property of the
University of Edinburgh and of the UK Natural Environment Research
Council.

20.5 Document Curator

20.6 Document URL

Keywords

BLACK SPRUCE

PICEA MARIANA

PHOTOSYNTHESIS

RESPIRATION

TRANSPIRATION