BOREAS TGB-12 Soil Carbon Data over the NSA Summary: The BOREAS TGB-12 team made measurements of soil carbon inventories, carbon concentration in soil gases, and rates of soil respiration at several sites to estimate the rates of carbon accumulation and turnover in each of the major vegetation types. TGB-12 data sets include soil properties at tower and selected auxiliary sites in the BOREAS NSA and data on the seasonal variations in the radiocarbon content of CO2 in the soil atmosphere at NSA tower sites. The sampling strategies for soils were designed to take advantage of local fire chronosequences, so that the accumulation of C in areas of moss regrowth could be determined. These data are used to calculate the inventory of C and N in moss and mineral soil layers at NSA sites and to determine the rates of input and turnover (using both accumulation since the last stand-killing fire and radiocarbon data). This data set includes physical parameters needed to determine carbon and nitrogen inventory in soils. The data were collected discontinuously from August 1993 to July 1996. 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 BOREAS TGB-12 Soil Carbon Data over the NSA 1.2 Data Set Introduction The data presented here include physical parameters needed to determine carbon and nitrogen inventory in soils (bulk density, %C (both as organic C and CaCO3), %N, C/N ratio in organic matter) as well as 14C measurements of organic matter. Soil moisture data (good only for the day of collection) and brief descriptions of soil horizons are also included. 1.3 Objective/Purpose The objectives of the research were: 1) To estimate rates of carbon input, turnover, and accumulation in the soils of each of the major vegetation types at the BOREAS study sites. The primary tool will be measures of 14C content in soils, litter, soil atmospheres, measurements of CO2 emissions from the soil. 2) To relate our estimates of dynamics of soil carbon to ecosystem models of the carbon cycle, to other measures of C cycling dynamics, to regional models of soil carbon accumulation, and to spatial and temporal models of soil moisture and drainage. 1.4 Summary of Parameters The key parameters include brief description of the sample/horizon (e.g. brown decomposed moss, clay), soil pH, soil moisture, bulk density, organic carbon and nitrogen content, inorganic carbon content, and radiocarbon (14C) content. 1.5 Discussion Carbon inventories and 14C give information are needed to determine C storage, as well as to determine the accumulation rate of C (in non-steady state systems) or the turnover rate of C (in systems where C turnover rate is less than soil or disturbance age). These data are checked using the isotopic composition of respired CO2 (which will reflect the 14C content of root respiration and decomposing organic matter), and by a knowledge of soil C inputs and losses. See section 3 (below) for details. 1.6 Related Data Sets BOREAS TGB-12 Radon222 Soil Data over the NSA BOREAS TGB-12 Soil Carbon Isotope Data over the NSA BOREAS TGB-01 Soil CH4 and CO2 Profile Data over the NSA BOREAS TGB-03 Soil CO2 and CH4 Profile Data over the NSA 2. Investigator(s) 2.1 Investigator(s) Name and Title Susan Trumbore Department of Earth System Science UC Irvine Jennifer Harden US Geological Survey Menlo Park, CA Eric Sundquist US Geological Survey Woods Hole, MA 2.2 Title of Investigation Input, Accumulation and Turnover of Carbon in Boreal Forest Soils 2.3 Contact Information Contact 1 Susan Trumbore Earth System Science University of California Irvine Irvine, CA Contact 2 Jennifer Harden US Geological Survey Menlo Park, CA 415-329-4949(Harden) 415-329-4940 (O'Neill) 415-329-4936 (Fax) harden@usgs.gov Contact 3 Eric Sundquist US Geological Survey Woods Hole, MA (508)457-2397 sundquist@nobska.wr.usgs.gov Contact 4 Greg Winston US Geological Survey Woods Hole, MA (508)457-2397 Contact 5 Sara Conrad Raytheon STX Corporation NASA Goddard Greenbelt, MD (301) 286-2624 (301) 286-0239 (FAX) Sara.Golightly@gsfc.nasa.gov 3. Theory of Measurements Soil moisture and soil C and N inventory are relatively common and straightforward measurements to make and will not be discussed in detail here. 14C is produced in the stratosphere by the 14N (n,p) 14C reaction. The 14C atom is oxidized rapidly to 14CO, which has a lifetime of months before it is oxidized to 14CO2. Most 14C production occurs in the stratosphere, but the long lifetime of CO2 enables 14CO2 to become well mixed throughout the troposphere. The steady state 14C content of the atmosphere is determined by the exchange of carbon in CO2 with that in ocean and biospheric reservoirs. Because of the relatively rapid cycling of carbon between the atmosphere and living biomass, most plants maintain a 14C specific activity (or 14C/12C ratio corrected for mass-dependent isotope fractionation effects) that equals that of atmospheric CO2. Similarly, animals reflect the 14C/12C of the plants (or animals) they consume. Upon the death of an organism, the 14C in its tissues is no longer replenished, and decays with a half life of 5730 years. If the tissue remains intact and isolated from exchange, the 14C/12C ratio may be used to indicate the time since the death of the organism. This is the basis for radiocarbon dating. Calculation of a radiocarbon age requires the assumption that the 14C content of the carbon originally fixed in plant tissues equaled that of the atmospheric CO2 in 1950 (0.95 times the activity of oxalic acid, or Modern). In fact, the 14C content of the atmosphere has varied with time because of changes in the production rate of 14C (cosmic ray flux and magnetic field variations) and because of changes in the distribution of carbon among ocean, biosphere and atmospheric reservoirs. These variations, deduced from the 14C content of cellulose of known age taken from the annual growth rings of trees, are generally less than 10% over the past 7,000 years. More recent changes in the 14C content of atmospheric CO2 have resulted from dilution by 14C-free fossil-fuel-derived carbon and by the production of 14C during atmospheric testing of thermonuclear weapons (bomb 14C). The latter effect dominates other natural and fossil fuel effects, as the atmospheric burden of 14C was approximately doubled in the few years preceding the implementation of the Nuclear Test Ban Treaty in 1964. This isotopic spike in the global carbon system provides a means for radiocarbon to be a useful tracer of carbon cycle processes on time scales of decades. We express 14C data in the geochemical D notation, the deviation in parts per thousand (per mil) from an absolute standard (95 times the activity of NBS oxalic acid measured in 1950). In this notation, zero equals the 14C content of 1895 wood, positive values indicate the presence of 'bomb' radiocarbon, and negative values indicate the predominance of C fixed from the atmosphere more than several hundred years ago. One important correction made in calculating the D14C value is the 13C concentration is needed to account for isotopic fractionation effects. For example, consider that the d13C difference between atmospheric CO2 and carbon fixed during photosynthesis by C3 plants is approximately 20â. Since the mass difference between 12 and 14 is twice that between 12 and 13, the fractionation of 14C will be roughly twice that of 13C. The 14C contents of a tree and the CO2 that it is fixing through photosynthesis will differ by approximately 40%. To account for fractionation effects, the sample (with d13C of d) and standard are corrected to a constant 13C content. The standard oxalic acid is corrected in the same way, to -19 per mil (see references in section 19 for more detail). For seeds and deciduous leaves that represent a single year's growth, the 14C content of recent samples may be used to determine the age of a sample to within a year or two. The 14C content of the sample is compared to the 14C record of atmospheric C in the Northern Hemisphere (see Burcholadze reference, in section 19 for an example). Evergreen needles, that may average several years' growth, will be less easily interpreted. For samples prior to 1960, radiocarbon ages in years may be calculated from the given Delta values as -8033*(ln(Delta*.995/1000 +1)). The conventional radiocarbon age must be converted to a calibrated age using the tree-ring based calibration curves that correct for known variations in atmospheric 14C over time. Both ages are usually rounded to the nearest decade or pentad. One application of radiocarbon to soil science lies is the 14C dating of charcoal and plant macrofossils to determine the accumulation rate of C in vertically aggrading soils (peat or moss). Unlike the closed systems represented by intact macrofossils, such as seeds or pollen, bulk Soil Organic Matter (SOM) is a heterogeneous reservoir with a variety of turnover times, to which carbon is continuously added (as new plant matter) and lost (as leached organic carbon or CO2). The radiocarbon content of SOM can not be interpreted as a 'date', but represents the average age of a carbon atom in this reservoir. The breakdown of C into faster and slower cycling pools may be determined by combining several approaches (see the articles in the reference list for more information). For soils that are accumulating organic matter, the Harden et al (1992) approach is used. The upward accumulation of carbon in feathermoss is modeled as a time sequence described by inputs and decomposition according to the following equation: dC/dt = I - kC (1) and Ct = I/k*(1- exp-k*t) (2) where C is carbon mass in units of mass per area, t is time, I is input rate in mass per area per year, and k is a decomposition coefficient in units of time-1. This approach assumes that decomposition is proportional to total mass. Two approaches were used: (1) measuring the dC/dt for mosses in stands of different ages of recovery since fire and fitting a curve of C and time with equation (2). At each identified post-burn site, transects were conducted across a variety of soil drainage classes to collect samples for inventories of biomass (trees and understory), accumulating slash, moss, and soil . (2) Using 14C to determine time to construct a curve of cumulative C inventory versus time at a single site (to which equation (2) is fit and I and k determined). In moss layers, we use the bomb-14C signal recorded in growing mosses (particularly Sphagnum); in humic and mineral soil layers, we use standard radiocarbon 'age' calculations. This approach assumes that time information, derived from macrofossils picked from the soil or moss sample, is representative of C dynamics for the bulk sample (not particularly true for feather mosses). 4. Equipment: 4.1 Sensor/Instrument Description Shovel, eyes, and sample bags Lab Equipment - Carlo Erba NA1500 carbon and nitrogen combustion analyzer; vacuum lines for purification of CO2 from combusted samples and graphite target preparation. Accelerator mass spectrometer used for 14C measurement is described in Southon et al., and Trumbore (in press) 4.1.1 Collection Environment Samples were collected under all environmental conditions. 4.1.2 Source/Platform Ground. 4.1.3 Source/Platform Mission Objectives None given. 4.1.4 Key Variables Soil temperature, sample depth, air temperature, site descriptions, del13C, del14C, CO2 Concentration, pH of the soil, volumetric and gravimetric soil, bulk density, and organic C and N. 4.1.5 Principles of Operation None given. 4.1.6 Sensor/Instrument Measurement Geometry None given. 4.1.7 Manufacturer of Sensor/Instrument None given. 4.2 Calibration 4.2.1 Specifications None given. 4.2.1.1 Tolerance None given. 4.2.2 Frequency of Calibration None given. 4.2.3 Other Calibration Information None given. 5. Data Acquisition Methods Special pits were equipped with thermistors (for monitoring soil temperature), Time Domain Reflectometry (TDR) probes (for monitoring soil water content), and soil gas probes (1/8" stainless steel tubing, perforated at one end and inserted 50 to 100 cm laterally into the soil pit wall, capped with 1/8" swagelock union fittings sealed with a septum). Further details are given in Winston et al. (submitted), and in section 4, below. Gas samples were obtained using gas-tight syringes, <10cc for soil CO2 (made using a Licor and the method of Davidson and Trumbore (1995) and CH4 measurements (made by FID gas chromatography). Soil samples are sieved (to <2mm) to remove rocks and large roots. We have quantified how much of this material was removed, and estimated the amount of C and N contained in the larger fractions. We report bulk density or carbon inventory data of the <2mm fraction, then add the >2mm portion back in to determine total bulk density and C inventory. In clay soils, this is a less important correction than in the sandy, gravelly soils (an example of where these data are needed is in the very gravelly soils found at the NSA YJP site). The samples are then homogenized, split, and in some cases ground to <100 mesh for chemical analyses. Laboratory measurements are described below: Bulk density. Bulk density is measured by determining the oven dry weight of a specific volume of soil. Field sampling utilized a 'box' of known area for collection of organic samples in upper soil horizons (such as mosses and litter layers). The area sampled was generally 12 cm x 12 cm. Samples of generally less than 7cm depth were taken. Note that the depths are not as well determined as the area, therefore areally expressed data (gC/cm2) should be used in these layers with more confidence than the bulk density data. In deeper soil layers, the bulk density data were measured using several small cores (roughly 3.5 cm diameter by 5 cm in length) that were pushed into the pit wall. %N, %C and %CaCO3. These measurements were performed with a commercial combustion analyzer (Carlo Erba NA1500). This instrument flash-combusts organic matter, oxides all C to CO2, and reduces all N to N2, then separates these gases chromatographically, and detects them with a thermal conductivity detector. The detector response for C and N is determined by combusting known quantities of C and N-containing pure compounds. Combusting empty capsules determine blanks, due to the presence of small amounts of C in the tin boats used to hold the sample (for C) or to small amounts of residual air (for N2). The combustion analyzer will oxidize both organic carbon and inorganic carbonates to CO2. The Lake Agassiz clays underlying many of the soils in the NSA contain significant amounts of inorganic CaCO3. To determine both CaCO3 and organic C content, each sample is analyzed twice: once for total carbon and once after it has been acidified to remove calcium carbonate. The %CaCO3 is then the Total %C minus the %C due to organics. Uncertainties are still being investigated for this equipment in the Irvine laboratory, but in general %C values are reproducible to +/- 0.05%C (organic) and %N. 14C. Carbon-14 is measured by Accelerator mass spectrometry of graphite targets prepared from CO2 (see one of several references, including Trumbore, 1995). Samples (of 1-2 mg carbon equivalent) are combusted in vacuum in quartz tubes with cupric oxide wire at 900 Celsius. The resulting CO2 is purified cryogenically, then reduced to graphite coating cobalt powder in a sealed Pyrex tube at 500-550 Celsius with zinc and titanium hydride powder. Accelerator mass spectrometry measurements were made at the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry. One sigma precision is usually +/- 8-10 per mil (.8-1.0 % Modern) and overall accuracy (based on repeated measurements of substandards prepared in the same way as samples) is 1.0 - 1.5% of Modern (10 - 15 per mil). We have noted what was measured for 14C, as specific fractions of the organic C are measured; these fractions include macrofossils (sphagnum leaves, fine root hairs, deciduous leaves, or charcoal), and chemically treated samples (residue after treatment with 0.5N HCl). 6. Observations 6.1 Data Notes None given. 6.2 Field Notes None given. 7. Data Description 7.1 Spatial Characteristics 7.1.1 Spatial Coverage The coordinate information for the various sampled sites is incomplete in the following lists. Where latitude and longitude coordinates exist, they are expressed in degrees and in reference to the North American Datum 1983 (NAD83). Sites with Coordinate Information ------------------------------------------------- Site Name/Label Latitude Longitude --------------- -------- ---------- GR1, Gillam Road 55.9055° N 97.7087° W GR2, Gillam Road 55.9082° N 97.7003° W GR3, Gillam Road: 55.906° N 97.7098° W GR4, Gillam Road: 55.9041° N 97.7063° W GR5, Gillam Road: 55.9055° N 97.7087° W Gillam Road Transect 55.9055° N 97.7087° W (The transect starts 100m SW of so82715C, where GR5 was sampled in detail and continues SW parallel to road with sampling approximately every 100m.) NSA-FEN: 55.91481° N 98.42072° W NSA-OBS: 55.88007° N 98.48139° W NSA-OBS: 55.88007° N 98.48139° W OJP1: 55.9287° N 98.6248° W OJP2: 55.9287° N 98.6248° W NSA-OJP: 55.92842° N 98.62396° W YJP1: 55.8952° N 98.28686° W NSA-YJP: 55.89575° N 98.28706° W FF1: 55.906° N 98.949° W SLJ1: 55.0667° N 98.5083° W Sites with No Coordinate Information Available ----------------------------------------------- Site Name/Label Location Description --------------- ------------------------ SLJ2 Transect, approximately 500m NNW of SLJ1 SLJ3 Transect, approximately 500m NNW of SLJ2 SLJ4 Transect, approximately 500m NNW of SLJ3 SLJ5 Transect, approximately 500m NNW of SLJ4 SLJ6 Transect, approximately 500m NNW of SLJ5 SLJ7 Transect, approximately 500m NNW of SLJ6 SLJ8 Transect, approximately 500m NNW of SLJ7 FFJ11 Footprint River, Footprint fire 1989 burn site, west side of Footprint River Bridge. FFJ12 Footprint River, Footprint River, 1989 burn, west side of Footprint River bridge, poorly drained site. SOAB1 No location information is available. SOBA0 Soab River 1956 burn, Site 0 on the transect; on the ridge of the SOAB 1956 burn. SOBA1 Soab River,1956 burn, South of Thompson on Hwy 391/6 just north of the Soab River on the west side of road. SOBA2 Soab River,1956 burn, 500m North of SOBA1 SOBA3 Soab River,1956 burn, 500m North of SOBA2 SOBA4 Soab River,1956 burn, 500m North of SOBA3 SOBA5 Soab River,1956 burn, 500m North of SOBA4 SOBA6 Soab River,1956 burn, 500m North of SOBA5 SOBA7 Soab River,1956 burn, 500m North of SOBA6 SOBA8 Soab River,1956 burn, 500m North of SOBA8 SOBA9 Soab River,1956 burn, 500m North of SOBA9 SOBA10 Soab River,1956 burn, 500m North of SOBA9 SOBA11 Soab River,1956 burn, 500m North of SOBA10 SOBA12 Soab River,1956 burn, South of Thompson just north of the Soab River. SOBA13 Soab River,1956 burn, South of Thompson just north of the Soab River on Hwy 391. SOBA14 Soab River,1956 burn, South of Thompson just north of the Soab River on Hwy 391. SOBH1 Soab River T3H No location information is available. FFJ1 Footprint fire 1989 burn site, far into Footprint burn, approximately 1Km north of FF1. FFJ2 near the Footprint RiverAlong the FFJ transect between FFJ1 and 3. YJPK1 Young Jack Pine, 1964 burn, Veldhuis Map name: Partridge soil; code pcp YJPK2 Young Jack Pine, 1964 burn, Veldhuis Map name: Partridge soil; code pcp BOG No location information available. OBS11 Old Black Spruce, Veldhuis Mapped name: Sipewisk. OBSF3 Old Black Spruce, End of TGB spur, 2.5 m east of small corral. OBSF4 Old Black Spruce, NW corner of boardwalk-TGB spur, 3m N and 3m W of intersection of spur and boardwalk. OBSP9 Old Black Spruce, Veldhuis mapped name: Nicohols Lake (NIC) OBS1 Old Black Spruce, Site is very wet, seasonally if not perennially somewhat frozen. Bear east on catwalk, south on first spur, east about 5m OBS2 near Old Black Spruce FW10 Gillam Road: 1992 burn, near 89/90 km marker on Gillam Road GRS1 Gillam Road: 1994 burn. GRC12 Gillam Road: unburned control for 1992 burn, near 89/90 km marker on Gillam Road, North side of road, across from 1992 burn. GRC13 Gillam Road: unburned control for 1992 burn, near 89/90 km marker on Gillam Road, North side of road, across from 1992 burn. GRJ11 Gillam Road: Cabin site, 1964 burn. Gillam Road: Near 89/90 marker on Gillam Road. FW3 Gillam Road: Near 89/90 marker on Gillam Road. FW9 Gillam Road: 1992 burn, near 89/90 km marker on Gillam Road 7.1.2 Spatial Coverage Map Not available. 7.1.3 Spatial Resolution None given. 7.1.4 Projection Not applicable. 7.1.5 Grid Description Not applicable. 7.2 Temporal Characteristics 7.2.1 Temporal Coverage Soil Carbon measurements were made from Aug 1993 to Jul 1996. 7.2.2 Temporal Coverage Map Not applicable. 7.2.3 Temporal Resolution The temporal resolution of the measurements was variable. 7.3 Data Characteristics Data characteristics are defined in the companion data definition file (tgb12scd.def). 7.4 Sample Data Record Sample data format shown in the companion data definition file (tgb12scd.def). 8. Data Organization 8.1 Data Granularity All of the BOREAS TGB-12 Soil Carbon Data over the NSA data are contained in one dataset. 8.2 Data Format(s) The 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 (tgb12scd.def). 9. Data Manipulations 9.1 Formulae 9.1.1 Derivation Techniques and Algorithms None. 9.2 Data Processing Sequence 9.2.1 Processing Steps None given. 9.2.2 Processing Changes None given. 9.3 Calculations 9.3.1 Special Corrections/Adjustments None given. 9.3.2 Calculated Variables None given. 9.4 Graphs and Plots None given. 10. Errors 10.1 Sources of Error None given. 10.2 Quality Assessment 10.2.1 Data Validation by Source None given. 10.2.2 Confidence Level/Accuracy Judgement 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 The data were examined for general consistency and clarity. 11. Notes 11.1 Limitations of the Data None given. 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 None given. 13. Future Modifications and Plans None given. 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) Elizabeth.Nelson@gsfc.nasa.gov 15.2 Data Center Identification See 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 TGB-12 soil carbon data are available from the EOSDIS ORNL DAAC (Earth Observing System Data and Information System) (Oak Ridge National Laboratory) (Distributed Active Archive Center). 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 17.1 Platform/Sensor/Instrument/Data Processing Documentation 17.2 Journal Articles and Study Reports Donahue, D. J., T. W. Linick and A. J. T. Jull, Isotope-ratio and background corrections for accelerator mass spectrometry radiocarbon measurements, Radiocarbon 32: 135-142 (1990). Goh, K. M., Carbon dating, chapter 8 (pp. 125 - 145), in, D. C. Coleman and B. Fry, Carbon isotope techniques, Academic Press, San Diego (1991) Sellers, P., F. Hall. 1994. Boreal Ecosystem-Atmosphere Study: Experiment Plan. Version 1994-3.0, NASA BOREAS Report (EXPLAN 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, K.F. Huemmrich. 1996. Boreal Ecosystem-Atmosphere Study: 1994 Operations. NASA BOREAS Report (OPS DOC 94). Sellers, P., F. Hall, 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 earlyresults from the 1994 field year. Bulletin of the American Meteorological Society. 76(9):1549-1577. Sellers, P., F. Hall. 1997. BOREAS Overview Paper. JGR Special Issue (in press). Southon, J., R., J. S. Vogel, S. E. Trumbore and others, Progress in AMS measurements at the LLNL spectrometer, Radiocarbon 34: 473 - 477 (1992). Stuiver, M. and H. Polach., Reporting of 14C data. Radiocarbon 19: 355-363 (1977). Taylor, R. E., A. Long, and R. Kra, eds., Radiocarbon after Four Decades: An interdisciplinary perspective, Springer-Verlag, NY,596 pp. (1992). Trumbore,S. E., Comparison of carbon dynamics in two soils using measurements of radiocarbon in pre-and post-bomb soils. Global Biogeochemical Cycles 7:275-290 (1993). 17.3 Archive/DBMS Usage Documentation 18. Glossary of Terms None given. 19. List of Acronyms AMS - Accelerator Mass Spectrometery 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 NSA - Northern Study Area ORNL - Oak Ridge National Laboratory PANP - Prince Albert National Park SSA - Southern Study Area URL - Uniform Resource Locator 20. Document Information 20.1 Document Revision Date Written: 24-Jul-1994 Last Updated: 04-Aug-1998 20.2 Document Review Date(s) BORIS Review: 25-Jul-1998 Science Review: 20.3 Document ID 20.4 Citation The TGB-12 team plans to publish the data in a USGS open file report. Please look for and reference the report or contact Susan Trumbore. 20.5 Document Curator 20.6 Document URL Keywords CO2, 14C, 13C, Soil Carbon, Organic Carbon, Inorganic Carbon TGB12_Soil_Carbon 08/20/98