BOREAS TF-11 Decomposition Data over the SSA-Fen Summary: The BOREAS TF-11 team collected several data sets in their efforts to fully describe the flux and site characteristics at the SSA-Fen site. This data set contains decomposition rates of a standard substrate (wheat straw) across treatments. The measurements were conducted as part of a 2x2 factorial experiment in which we added carbon (300 g m-2 as wheat straw) and nitrogen (6 g m-2 as urea) to four replicate locations in the vicinity of the TF-11 tower. The data are stored in tabular ASCII files. Table of Contents * 1 Data Set Overview * 2 Investigator(s) * 3 Theory of Measurements * 4 Equipment * 5 Data Acquisition Methods * 6 Observations * 7 Data Description * 8 Data Organization * 9 Data Manipulations * 10 Errors * 11 Notes * 12 Application of the Data Set * 13 Future Modifications and Plans * 14 Software * 15 Data Access * 16 Output Products and Availability * 17 References * 18 Glossary of Terms * 19 List of Acronyms * 20 Document Information 1. Data Set Overview 1.1 Data Set Identification SSA fen (TF-11) decomposition rates of a standard litter (wheat straw), including C, H, and N concentrations (tf11dcmp.txt) 1.2 Data Set Introduction This data set contains decomposition rates of a standard substrate (wheat straw) across treatments. The measurements were conducted as part of a 2x2 factorial experiment in which we added carbon (300 g m-2 as wheat straw) and nitrogen (6 g m-2 as urea) to four replicate locations in the vicinity of the TF-11 tower. 1.3 Objective/Purpose Much of the area within the boreal forest biome is comprised of wetlands, in which large carbon stores and high water tables drive fundamentally different atmospheric interactions than occur under the other forest types studied by BOREAS. One key difference is in the form carbon is emitted following soil microbial respiration--in wetlands, much of it is emitted as methane. Wetlands are the dominant influence of boreal forests on atmospheric methane. This study was undertaken in order to assess responses of methane emissions in northern wetlands to potential changes in plant productivity, nitrogen availability or both. Whiting and Chanton (1993) recently observed that methane emissions from wetlands across the globe are well related to net primary productivity. This may be for a variety of reasons, including enhanced plant transport, increased methanogenic substrates from root exudates, increased litter input cascading to enhanced substrate availability for methanogenesis, or enhanced C and N mineralization of decomposing residues. Previous work by us (Valentine et al. 1994) and others has shown that substrate availability is a key constraint on methane production in wetlands. The present study was an effort to test whether substrate manipulation results from laboratory studies could be mirrored under field conditions. 1.4 Summary of Parameters We report the mass loss of a standard plant material (wheat straw) over the course of ~50 days as a function of treatment and location. We also report the initial and final concentrations of carbon and nitrogen (mass basis). 1.5 Discussion These data were collected from a set of small locations within the fen, and therefore no one location represented the entire study site. In fact, the fen in which this work was conducted was characterized by a large scale gradient of vegetation, microtopography, and hydrology such that the study site itself is only representative of the portion of the fen in which it was located (i.e. the lower 1/3). 1.6 Related Data Sets BOREAS TE-06 Biomass Estimate Data BOREAS TE-18 Biomass Density Image of the SSA BOREAS TGB-03 Plant Species Composition Data over the NSA Fen 2. Investigator(s) 2.1 Investigator(s) Name and Title Contact 1 --------- David Valentine Department of Forest Sciences University of Alaska Fairbanks, AK (907) 474-7614 (907) 474-6184 (fax) ffdwv@aurora.alaska.edu Contact 2 --------- Sara Conrad Raytheon STX Corporation NASA/GSFC Greenbelt, MD (301) 286-2624 (301) 286-0239 (fax) Sara.Conrad@gsfc.nasa.gov 2.2 Title of Investigation Influence of substrate characteristics and other environmental factors on methane emissions from the BOREAS Southern Study Area fen site. III. Standard litter decomposition. 2.3 Contact Information Contact 1 David Valentine Department of Forest Sciences University of Alaska Fairbanks, AK (907) 474-7614 (907) 474-6184 (fax) ffdwv@aurora.alaska.edu Contact 2 --------- Sara Conrad Not applicableSA/GSFC Greenbelt, MD (301) 286-2624 (301) 286-0239 (fax) Sara.Conrad@gsfc.nasa.gov 3. Theory of Measurements Litter bags were constructed from fiberglass screen to hold ~3g of plant material. Once filled with wheat straw and weighed, they were placed within each of the treatment/location replicates and allowed to remain for ~50 days. They were then collected and re-weighed, and the fraction of the original weight remaining is reported in the accompanying file. 4. Equipment: 4.1 Sensor/Instrument Description Not applicable 4.1.1 Collection Environment The litter bags were set out around the end of July (21 July or 2 August), then retrieved on 17 September. Half the bags were placed on the surface of the peat, half were inserted 0.1 m below the surface. 4.1.2 Source/Platform Not applicable 4.1.3 Source/Platform Mission Objectives Recent papers (e.g. Whiting and Chanton 1993) have suggested that CH4 emissions are positively related to plant productivity. One possible mechanism by which enhanced NPP or other factors may result in higher CH4 emissions is through enhanced decomposition rates, perhaps indexing a more rapid substrate supply rate from fermentative processes. We therefore wanted to evaluate whether enhanced litter decomposition rates (ie, mass loss) covaried with CH4 emissions rates or varied as a function of our C and N additions. 4.1.4 Key Variables Name Unit Description FRAC Not applicable Fraction of wheat straw mass remaining C Not applicable C fraction of wheat straw H Not applicable H fraction of wheat straw N Not applicable N fraction of wheat straw 4.1.5 Principles of Operation Not applicable 4.1.6 Sensor/Instrument Measurement Geometry Not applicable 4.1.7 Manufacturer of Sensor/Instrument Not applicable 4.2 Calibration 4.2.1 Specifications 4.2.1.1 Tolerance Not applicable 4.2.2 Frequency of Calibration Not applicable 4.2.3 Other Calibration Information Not applicable 5. Data Acquisition Methods Approximately 3 g of wheat straw was sealed into each fiberglass mesh screen. Oven dry equivalent weights for each were determined based on additional subsamples. Two replicate bags for each treatment/platform combination were either laid on the surface or inserted 0.1 m into the peat near the end of July, then collected in mid-September. Each bag was oven-dried at 30 C for 48 h, then weighed. Subsamples were ground and analyzed using a Leco CHN analyzer for C, H, and N concentrations. Subsamples from the initial (undecomposed) wheat straw were similarly analyzed for C, H, and N concentrations: C_ADDED,N_ADDED,DURATION, REPLICATE_ID,LITTER_MASS_FRACTION,C_CONC,H_CONC,N_CONC Initial, 0,0,0,0,0,1,.446,.061,.005 6. Observations 6.1 Data Notes Vegetative growth lifted some of the bags off the peat surface during the decomposition period, and the resultant drying likely retarded those. 6.2 Field Notes None. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage All measurements were made along two transects identified by their location relative to the TF-11 micrometeorology tower: a north transect (NA and NB platforms) and a south transect (SA and SB platforms). All measurements were made within 70 m of the TF-ll tower whose North American Datum of 1983 (NAD83) coordinates are 53.80206°N, 104.61798°W. 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution The data are from point measurements at the given locations. 7.1.4 Projection Not applicable 7.1.5 Grid Description Not applicable 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Litter bags were placed either on 21 July 1994 (north transect) or 2 August 1994 (south transect). All bags were collected on 17 September 1994. 7.2.2 Temporal Coverage Map None. 7.2.3 Temporal Resolution Ideally, the litter bags would have been placed at the beginning of the growing season. Owing to a mis-communication from the PI to the field crew, the bags were not placed until much later than optimal. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tf11dcom.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tf11dcom.def). 8. Data Organization 8.1 Data Granularity All of the Decomposition Data over the SSA-Fen 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 single apostrophe marks. There are no spaces between the fields. Sample data records are shown in the companion data definition file (tf11dcom.def). 9. Data Manipulations 9.1 Formulae Not applicable 9.1.1 Derivation Techniques and Algorithms None. 9.2 Data Processing Sequence 9.2.1 Processing Steps None. 9.2.2 Processing Changes None. 9.3 Calculations 9.3.1 Special Corrections/Adjustments None. 9.3.2 Calculated Variables Not applicable 9.4 Graphs and Plots None. 10. Errors 10.1 Sources of Error The most obvious source of error was the tendency for the litter bags to be lifted above the peat surface by vegetative growth, potentially retarding decomposition through excessive drying. Other sources of error include solubilization of straw constituents resulting in overstatement of decomposition rate, exclusion of soil fauna by the bag screen itself, and moss or other growth in the bag causing a mass gain during the period. 10.2 Quality Assessment 10.2.1 Data Validation by Source Not applicable 10.2.2 Confidence Level/Accuracy Judgement Except for the bags that gained weight during the decomposition period, these data appear fairly robust. The afforementioned gainers should be deleted prior to analysis. 10.2.3 Measurement Error for Parameters Not applicable 10.2.4 Additional Quality Assessments None given. 10.2.5 Data Verification by Data Center Data were examined for general consistency and clarity. 11. Notes 11.1 Limitations of the Data See sections 9.1 and 10.1 11.2 Known Problems with the Data None given. 11.3 Usage Guidance See sections 9.1 and 10.1 11.4 Other Relevant Information None given. 12. Application of the Data Set Several avenues are being pursued in publications now being produced to answer the following questions: 1. How do CH4 flux measurements compare by technique used in measurement? 2. How and why do CH4 flux measurements vary through time and across the landscape? 3. Does plant productivity limit CH4 emissions? 13. Future Modifications and Plans None. 14. Software 14.1 Software Description We used only commercially available software, mostly the Quattro Pro spreadsheet. 14.2 Software Access Not applicable. 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 Comma delimited ASCII text files. 17. References 17.1 Platform/Sensor/Instrument/Data Processing Documentation None. 17.2 Journal Articles and Study Reports Klinger, L.F., P.R. Zimmerman, J.P. Greenberg, L.E. Heidt, and A.B. Guenther. 1994. Carbon trace gas fluxes along a successional gradient in the Hudson Bay lowland. J. Geophys. Res. 99:1469-1494. 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. 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. Whiting G.J., Chanton J.P. 1993. Primary production control of methane emission from wetlands. Nature 364:794-5. 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 GSFC - Goddard Space Flight Center NASA - National Aeronautics and Space Administration ORNL - Oak Ridge National Laboratory URL - Uniform Resource Locator SSA - BOREAS Southern Study Area 20. Document Information 20.1 Document Revision Date Written: 29-Jan-1997 Last Updated: 08-Oct-1998 20.2 Document Review Date(s) BORIS Review: 08-Oct-1998 Science Review: 20.3 Document 20.4 Citation Valentine, D.W. 1996. Influence of substrate characteristics and other environmental factors on methane emissions from the BOREAS Southern Study Area fen site. III. Standard litter decomposition. 20.5 Document Curator 20.6 Document URL TF11_Decomp.doc 10/09/98