BOREAS TE-08 Aspen Bark Chemistry Data

Summary

The BOREAS TE-08 team collected pigment density data from aspen bark and
leaves from four sites within the BOREAS SSA from 24-May-1994 to
16-Jun-1994 (IFC-1), 19-Jul-1994 to 08-Aug-1994 (IFC 2), and 30-Aug-1994
to 19-Sep-1994 (IFC-3). One to nine trees from each site were sampled
during the three IFCs. Each tree was sampled in five different locations
for bark pigment properties: basal stem section, which was any bark
sample taken below one-half the tree height; upper stem section, which
was any bark sample taken from the main stem above one-half the tree
height; bark taken from branches up to 3 years old; a 2-year old branch
segment; and a 1-year old branch segment. Additionally, a limited number
of leaves were collected. Bark samples were removed from the stem of the
tree, placed in ziplock bags, and transported to UNH, where they were
processed and analyzed by a spectrophotometer.

In each data file, samples are identified by Site, date, Tree#, and
Sample Location (see 1st paragraph above). Pigment density values are
normalized to mg/m^2^. Density values for the following pigments are
provided: Chl a, Chl b, Total Chl (Chl a+b), Carotenoids, Chl a to b
ratio, and the Total Chl to carotenoids ratio.

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-08 Aspen Bark Chemistry Data

1.2 Data Set Introduction

These data are pigment densities for aspen bark samples and aspen leaf
samples collected from four sites within the BOReal Ecosystem-Atmosphere
Study (BOREAS) Southern Study Area (SSA) during the three Intensive
Field Campaigns (IFCs) of 1994. Each tree was divided into five
different bark sampling locations: basal stem, upper stem, branch,
2-year old branches, and 1-year old branches. Additionally, several
leaves were also measured for pigment density for comparison to bark
data.

1.3 Objective/Purpose

The purpose of this work was to understand the potential influence of
aspen bark photosynthesis on bark spectra and on the carbon budget of
boreal aspen stands.

1.4 Summary of Parameters

Each data set contains the sample location, the chlorophyll (chl) A
density, chl B density, total chl density, carotenoid density, ratio of
chl A/chl B, and the ratio of total chl/carotenoid.

1.5 Discussion

The bark of aspen (Populus tremuloides) is green and photosynthetic. The
phenomenon of bark photosynthesis in aspen has been studied extensively;
it has been shown that bark photosynthesis can account for between 5-40%
of whole tree photosynthesis. BOREAS used remote sensing systems as a
primary means for data collection to better understand the
ecosystem-atmosphere interactions. Aspen is a dominant forest cover
type, especially in the SSA. Therefore, bark spectral properties could
significantly affect data collected and analyzed by remote sensing
instruments in BOREAS. The photosynthetic pigment content of the bark
affects the spectral properties, and the pigments densities were
quantified.

This study was undertaken to quantify the pigment and spectral
properties of aspen bark samples (spectral data are presented in
separate files with a separate documentation file). The results of this
study provide an initial understanding of the potential influence of
aspen bark photosynthesis on remotely collected data and carbon budget
for aspen stands. A more intensive study should be conducted to scale
lab-based spectral measurements to airborne and spaceborne platforms.
Additionally, direct measurements of bark photosynthesis would be
required to determine the significance to the boreal carbon budget.

The quality of the pigment data is believed to be good. Comparisons with
data reported by other researchers who have studied aspen bark
photosynthesis show similar results. Additionally, leaf pigment samples
correspond to measurements taken by other BOREAS researchers, showing
that the bark samples should be of good quality.

1.6 Related Data Sets

BOREAS TE-08 Aspen Bark Spectral Reflectance Data

BOREAS TE-09 NSA Leaf Chlorophyll Density

BOREAS TE-10 Leaf Chemistry Data

2\. Investigator(s)

2.1 Investigator(s) Name and Title

Dr. Slava Kharuk, Scientist

Dr. Barret N. Rock, Associate Professor

2.2 Title of Investigation

Aspen Bark Input in Tree-Atmosphere Interactions

2.3 Contact Information

[Contact 1:]{.underline}

Mr. Shannon Spencer

Complex Systems Research Center

University of New Hampshire

Durham, NH

\(603\) 862-1792

\(603\) 862-0188 fax

shannon.spencer@unh.edu

[Contact 2:]{.underline}

Dr. Barret N. Rock

Department of Natural Resources

Complex Systems Research Center

University of New Hampshire

Durham, NH

\(603\) 862-1792

barry.rock@unh.edu

[Contact 3]{.underline}:

Andrea Papagno

Raytheon ITSS

NASA GSFC

Greenbelt, MD

\(301\) 286-3134

\(301\) 286-2039 (fax)

Andrea.Papagno@gsfc.nasa.gov

3\. Theory of Measurements

Bark pigment characteristics, primarily chlorophylls a and b, are
important molecule complexes in the process of photosynthesis and carbon
assimilation. Therefore, in order to better understand the phenomenon of
bark photosynthesis and how it relates to the bark spectral properties,
pigment extractions were made of bark and leaf samples. These samples
were taken at the same time and place as spectral samples (see BOREAS
TE-08 Aspen Bark Spectral Reflectance Data).

4\. Equipment

4.1 Sensor/Instrument Description

A Beckman DU-7 spectrophotometer was used to make absorbance
measurements. Calibrated 1-cm quartz vials were used for measurements
within the spectrophotometer.

4.1.1 Collection Environment

Bark and leaf samples were collected from the field. Measurements took
place in laboratory conditions.

4.1.2 Source/Platform

None given.

4.1.3 Source/Platform Mission Objectives

None given.

4.1.4 Key Variables

Chl a, chl b, carotenoid densities.

4.1.5 Principles of Operation

Absorption due to light extinction (see Lichtenthaler, 1987; Gregory,
1989).

4.1.6 Sensor/Instrument Measurement Geometry

None given.

4.1.7 Manufacturer of Sensor/Instrument

Beckman Spectrophotometer, Model DU-7

Beckman Coulter, Inc.

4300 N. Harbor Boulevard

P.O. Box 3100

Fullerton, CA 92834-3100

\(800\) 742-2345

\(800\) 634-4366 (fax)

4.2 Calibration

4.2.1 Specifications

Absorption is calibrated based on use of a 100% dimethyl sulfoxide
(DMSO) blank in a standard 1 cm quartz cuvette.

4.2.1.1 Tolerance

None given.

4.2.2 Frequency of Calibration

A 100% DMSO blank was used for calibration once every 10 measurements.

4.2.3 Other Calibration Information

None.

5\. Data Acquisition Methods

Bark samples from different locations within the tree were collected and
analyzed to determine chl a, chl b, total chl (chl a+b), and carotenoid
concentrations. At the Paddockwood field site, within a day following
collection, bark and leaf samples were removed from the tree using a
cork borer of known diameter. Bark sections were peeled off the stem or
branch wood, placed in ziplock bags with wet napkins, and kept cool
until samples could be processed. These samples were then cut into
pieces and added to 4 ml DMSO in capped glass vials, a standard
procedure described by Lichtenthaler (1987) and Hixcox and Israelstam
(1979) for chlorophyll extraction. Samples were allowed to extract in
darkened conditions for 48 hours and were then kept frozen until
processing could take place at the University of New Hampshire (UNH).
Vials were kept frozen during transport to UNH and were measured within
1 week of arrival (except for IFC-1 samples; see Section 6.1).

At UNH, the extracted solutions were refrigerated for 30 minutes prior
to measurement. The spectrophotometer was calibrated using 100% DMSO in
a quartz cuvette. Four ml of extract were placed in a 1-cm quartz
cuvette, and absorption was measured at four different wavelength
positions. The sample was returned to the glass vial. The quartz cuvette
was rinsed between samples with 80% acetone and the spectrophotometer
was recalibrated every 10 samples. Extract solution absorbance was
measured with a Beckman DU-7 spectrophotometer at 470.0 nm, 646.8 nm,
663.2 nm, and 750.0 nm (Lichtenthaler, 1987; Spencer, 1996). The results
were printed and then entered into a spreadsheet. Absorbance values were
used to calculate pigment concentrations using standard extinction
equations reported by Lichtenthaler (1987) (see also Spencer, 1996).
Absorption at 750.0 nm (value at 750 should be made equal to zero and
the difference is applied to the other wavelengths) was used to
calibrate other absorbance values (Middleton, personal communication;
Spencer, 1996). Pigment concentration values were then normalized to
mg/dm^2^ using the known amount of extraction used and the original
surface area of the sample extracted.

6\. Observations

6.1 Data Notes

Samples from IFC-1 were measured shortly after returning from Canada.
However, data were erroneous because of a malfunctioning siphon that was
initially used to fill and rinse the cuvette with the sample solution.
This problem was noted and corrected. IFC-1 samples had been stored at 4
°C and were remeasured in early August 1994 following correction of the
problem.

The authors conducted some preliminary research on bark area leaf area
ratios that is not reported here. This information can be found in
Spencer, 1996.

6.2 Field Notes

Samples were collected at field sites, placed in ziplock bags, and kept
cool until processing. Extractions were conducted at the field lab and
were then frozen (about 4 °C) until they were measured with the
spectrophotometer at UNH.

7\. Data Description

7.1 Spatial Characteristics

7.1.1 Spatial Coverage

Four sites were sampled during the three 1994 IFCs. Not all sites were
sampled during each IFC because of destructive sampling logistics. Two
BOREAS tower sites were used: Old Aspen (SSA-9OA) and Young Aspen (YA).
Additionally, the originally identified BOREAS YA site was sampled
during all three IFCs and is identified in these data sets as the Young
Aspen-Auxiliary 04 site (YA-AUX04), and a non-BOREAS mixed aspen and
white spruce site is identified as YA-AUX07. One to five trees were
destructively harvested during each IFC.

The following is sample collection information at the four SSA
locations:

1\) SSA-9OA: One tree was harvested during IFC-2. Branch samples only
were collected during IFC-1, and no samples were collected from the
SSA-9OA during IFC-3 because of the logistics of destructive sampling.

2\) YA-AUX04: Three trees were destructively harvested during each of
the three IFCs.

3\) YA: Five trees were harvested during IFC 2 and 3.

4\) YA-AUX07: This is a non-BOREAS site that exists within the BOREAS
SSA and was established in order to harvest a second mature (\>60 yr.
old tree) aspen stand for TE-08 research. This site was a mixed site of
mature aspen overstory and white spruce understory. It was located on
the property of Snow Castle Lodge approximately 3 km N of the SSA-YA
site (see Spencer, 1996, for more details). One tree was harvested from
this site during IFC-3.

The SSA measurement sites and their associated North American Datum of
1983 (NAD83) coordinates are:

SSA-9OA, site id C3B7T, Lat/Long: 53.62889 N, 106.19779 W, Universal
Tranverse Mercator (UTM) Zone 13, N: 5,942,899.9 E: 420,790.5.

YA, site id D0H4T, Lat/Long: 53.65601 N, 105.32314 W, UTM Zone 13, N:
5,945,298.9 E: 478,644.1.

YA-AUX04, site id D6H4A, Lat/Long: 53.70828 N, 105.31546 W, UTM Zone 13,
N: 5,951,112.1 E: 479,177.5.

YA-AUX07, Located 3 km N of SSA-YA on the property of Snow Castle Lodge,
UTM Zone 13. This was a mixed site of mature aspen overstory (\>60 yrs)
and white spruce understory.

7.1.2 Spatial Coverage Map

Not available here. See Spencer, 1996.

7.1.3 Spatial Resolution

These data are point measurements at the given location.

7.1.4 Projection

None given.

7.1.5 Grid Description

None given.

7.2 Temporal Characteristics

7.2.1 Temporal Coverage

These data were collected from 24-May-1994 to 16-Jun-1994 (IFC-1),
19-Jul-1994 to 08-Aug-1994 (IFC-2), and 30-Aug-1994 to 19-Sep-1994
(IFC-3).

7.2.2 Temporal Coverage Map

None given.

7.2.3 Temporal Resolution

Each site was visited once.

7.3 Data Characteristics

Data characteristics are defined in the companion data definition file
(te08bchm.def).

7.4 Sample Data Record

Sample data format shown in the companion data definition file
(te08bchm.def).

8\. Data Organization

8.1 Data Granularity

All of the bark chemistry data are in one file.

8.2 Data Format(s)

The data files contain 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 records are shown in the companion data definition file
(te08bchm.def).

9\. Data Manipulations

9.1 Formulae

Absorption data were calibrated with absorption data from the 750 nm
band and were then input into the extinction equations listed in Section
9.1. These values were then normalized for the amount of solution used
and the surface area of the sample to arrive at a figure in mg/dm^2^.
See section 9.2.1 for further details.

Extinction coefficients are from Lichtenthaler (1987):

\[chl a\]=12.25A(663.2)-2.79A(646.8) (1)

\[chl b\]=21.50A(646.8)-5.10A(663.2) (2)

\[chl a+b\]=\[chl a\]+\[chl b\] (3)

\[carotenoids\]=(1000A(470)-1.82\[chl a\]-85.02\[chl b\])/198 (4)

where A(wavelength) is the absorption at the specified wavelength.

9.1.1 Derivation Techniques and Algorithms

Not applicable.

9.2 Data Processing Sequence

9.2.1 Processing Steps

1\) Absorption results were entered into a spreadsheet.

2\) Absorption at 750.0 nm (value at 750 was made equal to zero and the
difference was applied to the other wavelengths) was used to calibrate
other absorbance values (Middleton, personal communication; Spencer,
1996).

3\) Pigment concentration values were then normalized to mg/dm^2^ using
the known amount of extraction used and the original surface area of the
sample extracted.

4\) Absorbance values were used to calculate pigment concentrations
using standard extinction equations reported by Lichtenthaler (1987)
(see also Spencer, 1996).

5\) As part of its data integration efforts, BORIS staff converted the
pigment concentration values to mg/m^2^ to be compatible with other
similar measurements.

9.2.2 Processing Changes

None given.

9.3 Calculations

9.3.1 Special Corrections/Adjustments

Data were corrected with the measurement at 750 nm because of the purity
of the DMSO and the possibility for debris in the extract solution. The
value at 750 nm should be equal to zero for chlorophyll and pigment
absorption. If the absorption value at 750 nm was greater than 0.01, the
sample was rerun or discarded.

9.3.2 Calculated Variables

See Sections 9.1 and 9.3.1.

9.4 Graphs and Plots

None given.

10\. Errors

10.1 Sources of Error

Error could have been created by the calibration discussed in Section
9.3.1. The extraction solution should have been filtered to avoid this
problem. However, discussions with other BOREAS teams measuring
chlorophyll concentration showed TE-08's calibration method discussed in
Section 9.3.1 to be an acceptable practice.

10.2 Quality Assessment

Several tests were conducted to be sure that consistent, reliable data
were collected by the instrument. The tests included comparisons of
light absorption to a standard of 100% DMSO and comparisons of results
with those of TE-10. Our data appear to be consistent with TE-10's
results.

10.2.1 Data Validation by Source

10.2.2 Confidence Level/Accuracy Judgment

The data appear to be good. Leaf chlorophyll data were checked against
those of TE-10 and found to be not significantly different.

10.2.3 Measurement Error for Parameters

None given.

10.2.4 Additional Quality Assessments

All data were checked for potential problems and discarded if problems
were evident.

10.2.5 Data Verification by Data Center

Data were examined for general consistency and clarity.

11\. Notes

11.1 Limitations of the Data

These data are calculated on an area basis rather than a weight basis
because of the bark tissue heterogeneity.

11.2 Known Problems with the Data

None given.

11.3 Usage Guidance

None given.

11.4 Other Relevant Information

None given.

12\. Application of the Data Set

These data provide information on the chlorophyll density of aspen bark.
This information can be scaled up to the whole tree level to determine
the amount of whole tree chlorophyll found in the bark tissue. This
gives a preliminary indication as to the importance of bark
photosynthesis on a whole tree/stand level. More work should be done in
this area to determine bark photosynthesis significance to aspen carbon
dynamics. Gas exchange measurements should be conducted on aspen bark
during different times of the year. See Spencer, 1996, for more
discussion.

13\. Future Modifications and Plans

These data have been presented in more detail in Spencer, 1996.

14\. Software

14.1 Software Description

Quattro Pro 4.0 was used for most analyses and then Excel 5.0 was used
for the final and summative analyses. For a statistical package TE-08
used Stata Pro 4.0.

14.2 Software Access

None given.

15\. Data Access

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-08 bark chemistry 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 file.

17\. References

17.1 Platform/Sensor/Instrument/Data Processing Documentation

Beckman Spectrophotometer Manual, Beckman Spectrophotometer, Model DU-7,
Beckman Coulter, Inc.,Fullerton, CA 92834-3100.

17.2 Journal Articles and Study Reports

Gregory, R.P. 1989. Photosynthesis. Chapman and Hall. NY, NY. 160 pp.

Hixcox, J.D. and G.F. Israelstam. 1979. A method for the extraction of
chlorophyll from leaf tissue without maceration. Can. J. Bot.
57:1332-1334.

Lichtenthaler, H.K. 1987. Chlorophylla and carotenoids: pigments of

photosynthetic biomembranes. Methods in Enzymology. 148:349-382.

Rock, B.N. et al. High-spectral resolution field and laboratory optical
reflectance measurements of red spruce and eastern hemlock needles and
branches. 1994. Remote Sensing of Environment. 47:176-189.

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. Boreal Ecosystem-Atmosphere Study
(BOREAS): an overview and early results from the 1994 field year.
Bulletin of the American Meteorological Society. V76: 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. 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 (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.

Spencer, S.L. 1996. Anatomical, Pigment, and Spectral Evidence of
Cortical Photosynthesis in Populus tremuloides from the Canadian Boreal
Region. Master\'s Thesis, Dept. Nat. Res., University of New Hampshire,
186 pp.

Spencer, S.L. and B.N. Rock. 1996. Assessing aspen bark carbon
assimilation in the boreal region. In Proceedings of 22nd Conference on
Agricultural and Forest Meteorology with Symposium on Fire and Forest
Meteorology. 28 January-2 February, 1996, Atlanta, Georgia. American
Meteorological Society, pp:86-89.

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

CHL - Chlorophyll

CD-ROM - Compact Disk-Read-Only Memory

DAAC - Distributed Active Archive Center

DMSO - Dimethyl Sulfoxide

EOS - Earth Observing System

EOSDIS - EOS Data and Information System

FOV - Field-of-View

GSFC - Goddard Space Flight Center

HTML - HyperText Markup Language

IFC - Intensive Field Campaign

NAD83 - North American Datum of 1983

NASA - National Aeronautics and Space Administration

NOAA - National Oceanic and Atmospheric Administration

NSA - Northern Study Area

OA - Old Aspen

ORNL - Oak Ridge National Laboratory

PANP - Prince Albert National Park

SSA - Southern Study Area

TE - Terrestrial Ecology

UNH - University of New Hampshire

URL - Uniform Resource Locator

UTM - Universal Transverse Mercator

YA - Young Aspen

YA-AUX - Young Aspen-Auxilliary

20\. Document Information

20.1 Document Revision Date(s)

Written: 21-May-1997

Last Updated: 09-Feb-1999

20.2 Document Review Date(s)

BORIS Review: 25-Oct-1998

Science Review: 26-May-1998

20.3 Document ID

None.

20.4 Citation

Shannon L. Spencer and Barrett N. Rock, both of the Complex Systems
Research Center at UNH.

20.5 Document Curator

20.6 Document URL

[Keywords]{.underline}

Aspen

Bark chlorophyll

Bark photosynthesis

Chlorophyll

Pigment absorption

Populus tremuloides