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/m2. 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: 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: 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: 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/dm2 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/dm2. 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/dm2 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/m2 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 Aspen Bark chlorophyll Bark photosynthesis Chlorophyll Pigment absorption Populus tremuloides TE08_Bark_Chem.doc 03/03/99