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BASIN TCP Stable Isotope Composition of CO2 in Terrestrial Ecosystems
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Revision date: February 10, 2010

Summary:

This data set reports stable isotope ratio data of CO2 (13C/12C and 18O/16O) associated with photosynthetic and respiratory exchanges across the biosphere-atmosphere boundary. Measurements were made at selected AmeriFlux sites: Harvard Forest, Howland Forest, Rannells Flint Hills Prairie, Niwot Ridge Forest, and the Wind River Canopy Crane Site, which span the dominant ecosystem types of the United States. These data were collected periodically from 2001 through 2004 and are available as an ASCII comma separated file.

The goal of this Terrestrial Carbon Processes (TCP) project  is to better capture isotopic effects of ecosystem-atmosphere interaction at diurnal, seasonal and interannual time scales by long-term monitoring 13C of CO2 exchange with the atmosphere at weekly intervals. Photosynthesis and respiration in terrestrial ecosystems have opposite effects on diurnal and seasonal patterns on atmospheric CO2 concentration and isotope ratios. This isotopic variation contains information about the functioning of different terrestrial ecosystems.

Specifically, this research addresses the following fundamental questions to meet the need to have a stronger characterization of the isotopic composition of CO2 in terrestrial biosphere-atmosphere exchange identified by the U.S. Carbon Cycle Science Plan (CCWG, 1999):

This TCP project contributes to The Biosphere - Atmosphere Stable Isotope Network (BASIN) (http://basinisotopes.org), an umbrella program aimed at improving our understanding of carbon and water cycle processes at the ecosystem, regional, and global scales. Data sharing and integration will allow for cross-site comparisons and provide an opportunity to assess any continental or global effects.

Additional information about AmeriFlux and the measurement sites can be obtained from the program web site at http://ameriflux.lbl.gov/SitePages/Home.aspx.

Site Supplemental Information

A table of measurement sites cross referenced to FLUXNET sites and linked to the FLUXNET web site with supplemental information is included in Section 5.

Acknowledgement: The Terrestrial Carbon Processes (TCP) Program research performed by the Ehlringer Lab at the University of Utah, James Ehlringer, Director, was supported by the Office of Science (BER), U.S. Department of Energy, under Grant No. DE-FG03-00ER63012.

Data Citation:

Cite this data set as follows:

 Ehleringer, J.R. and C.T. Lai. 2010. BASIN TCP Stable Isotope Composition of CO2 in Terrestrial Ecosystems. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, U.S.A. doi: 10.3334/ORNLDAAC/963

Table of Contents:

1. Data Set Overview:

This data set reports stable isotope ratio data of CO2 (13C/12C and 18O/16O) associated with photosynthetic and respiratory exchanges across the biosphere-atmosphere boundary. Measurements were made at selected AmeriFlux sites: Harvard Forest, Howland Forest, Rannells Flint Hills Prairie, Niwot Ridge Forest, and Wind River Canopy Crane Site, which span the dominant ecosystem types of the United States. These data were collected periodically from 2001 through 2004 and are available as an ASCII comma separated file.

2. Data Characteristics:

These data were collected periodically from 2001 through 2004 and are available as an ASCII comma separated file.


Data file description :  TCP_2001_2004_20091117.csv

Column Heading Units or format Description Method
TCP_site character Sampling site name  
TCP_location character Sampling location within site  
Date_sampled mm/dd/yyyy Date sample collected  
Time_sampled hh:mm Time sample collected.  Missing code = -9999.  
Time_zone character Local standard time zone  
TCP_Contact character Sampling and analysis information contact  
Sample_type character Sampled medium is air.
When TCP_source = 2001-2004: daytime, nighttime, or tank air may be specified.
When TCP_source= TCP_2004: only air is specified.
Sample_type  =  "tank air" indicates a  calibration run and data values should not be combined with ambient samples.
Sample_ID character Data provider designation.    Missing code = "Not provided"  
Flask_position numeric Sampling Strategies: Intial approach -
Flask 1: control flask
Flask 2-3: mid-afternoon samples from level 3 (top of the canopy)
Flask 4-15: nightime samples beginning an hour after sunset from level 1 and 2 (inside the canopy)

Beginning in July 2003, four flasks are collected in the mid-afternoon. See Lai et al. (2003; 2004) for more information on sampling strategy.     Missing code = -999.
Flasks were collected by an automated sampling system (Schauer et al. 2003).
Height meters Sampling height in meters.    Missing code = -999.  
CO2_air ppm CO2 concentration in flask sample.WMO scale.  Missing code = -999.99 Measured with a bellow/IRGA system (Bowling et al. 2001).
del_13C_CO2 per mil Isotopic ratio of 13C/12C in carbon dioxide. Pee Dee Belemnite (PDB) standard. Missing code = -999.99 Flasks were analyzed for isotope ratios at the Stable Isotope Ratio Facility for Environmental Research (SIRFER) at the University of Utah using a continuous-flow isotope ratio mass spectrometer system (Precon attached to a Delta S, San Jose , CA.)
del_13_standard character VPDB scale  
del_18O_CO2 per mil Isotopie ratio of 18O/16O in carbon dioxide. Standard Mean Ocean Water (SMOW) standard.
Missing code = -999.99
Flasks were analyzed for isotope ratios at the Stable Isotope Ratio Facility for Environmental Research (SIRFER) at the University of Utah using a continuous-flow isotope ratio mass spectrometer system (Precon attached to a Delta S, San Jose , CA.)
del_18O_std character VSMOW scale  
TCP_source character Marker for data provider source  
Orig_TCP_data_file character Original data file name as received from provider. Numerous data files were combined  by the Data Center into this single file and checked for consistency.
Notes character Supplemental sampling and analysis information  If the Notesvalue is "bad point" or "questionable" then related data values have been set to missing.
Ecosystem character Data provider designation  
Species character Data provider designation.  
Data_source1 character Data provider information.  
Data_source2 character Data provider information.  

Example data records:

TCP_site,TCP_location,Date_sampled,Time_sampled,Time_zone,TCP_Contact,Sample_type,Sample_ID,Flask_position,Height,
CO2_air,del_13C_CO2,del_13C_std,del_18O_CO2,del_18O_std,TCP_source,Orig_TCP_data_file,Notes,Ecosystem,Species,
Data_source1,Data_source2

character,character,mm/dd/yyyy,hh:mm,character,character,character,character,numeric,meters,
ppm,per mil,character,per mil,character,character,character,character,character,character,
character,character
...

Harvard Forest,EMS Annex Walk-Up Tower (130m SW of the EMS eddy flux tower),23/08/2001,20:52,EST,
"Chun Ta Lai, Jim Ehleringer",tank air,A131 (15),15,-999,396.00,-30.18,PDB,2.29,SMOW,2001-2004,
01_08_HV_auto_2.xls,,broadleaf forest,"Quercus velutina, Acer rubrum",DOE/TCP project - Stable Isotope Analyses at the Harvard Forest

Harvard Forest,EMS Annex Walk-Up Tower (130m SW of the EMS eddy flux tower),23/08/2001,15:24,EST,
"Chun Ta Lai, Jim Ehleringer",daytime air,5E (1),1,22.4,370.40,-8.19,PDB,40.62,SMOW,2001-2004,
01_08_HV_auto_2.xls,,broadleaf forest,"Quercus velutina, Acer rubrum",DOE/TCP project - Stable Isotope Analyses at the Harvard Forest
...
Wind River,Crane,10/09/2004,19:42,PST,"Chun Ta Lai, Jim Ehleringer",air,AAA4.5,5,0.5,
494.55,-12.83,PDB,39.06,SMOW,TCP_2004,040915_WR_auto_1.xls,,conifer forest,Pseudotsuga menziesii,
DOE/TCP project,

Wind River,Crane,10/09/2004,19:47,PST,"Chun Ta Lai, Jim Ehleringer",air,A20.6,6,30,
413.02,-10.21,PDB,40.43,SMOW,TCP_2004,040915_WR_auto_1.xls,,conifer forest,Pseudotsuga menziesii,
DOE/TCP project,

Please note that line breaks were added to improve readability and are not in the data file.

Site boundaries: (All latitude and longitude given in decimal degrees)

Site (Region) Westernmost Longitude Easternmost Longitude Northernmost Latitude Southernmost Latitude Geodetic Datum
Howland Forest (Main Tower), ME USA -68.740278 -68.740278 45.2040700 45.2040700 World Geodetic System, 1984 (WGS-84)
Harvard Forest EMS Tower (HFR1), MA USA -72.171478 -72.171478 42.5377556 42.5377556 World Geodetic System, 1984 (WGS-84)
Niwot Ridge (LTER NWT1), CO USA -105.546403 -105.546403 40.0328778 40.0328778 World Geodetic System, 1984 (WGS-84)
Niwot Ridge (LTER NWT2), CO USA -105.546944 -105.546944 40.0325000 40.0325000 World Geodetic System, 1984 (WGS-84)
Rannells Ranch (ungrazed), KS USA -96.523000 -96.523000 39.1390000 39.1390000 World Geodetic System, 1984 (WGS-84)
Wind River Crane Site, WA USA -121.9519111 -121.9519111 45.8204889 45.8204889 World Geodetic System, 1984 (WGS-84)

Time period:

3. Data Application and Derivation:

Stable isotope ratios of CO2 are recognized as a key element in improving our interpretations of the carbon cycle at the ecosystem, regional, and global scales. The 13C and 18O analyses of CO2 have been an element of the NOAA Cooperative Air Sampling Network - global flask network (http://www.esrl.noaa.gov/gmd/ccgg/flask.html) for over a decade, where these data are essential in partitioning fluxes within the global carbon cycle. The global flask network is an international effort which includes regular discrete samples from the 4 NOAA ESRL/GMD baseline observatories, cooperative fixed sites, and commercial ships. Air samples are collected approximately weekly from a globally distributed network of sites.

Stable isotope analyses are now becoming integrated into regional and ecosystem carbon cycle studies. In part this lag has been because terrestrial surfaces can have large diurnal, vertical, and seasonal impacts on CO2 concentration and isotope ratios. Much of this variation is filtered out in a flask network that is largely focused at marine sampling sites. The U.S. Carbon Cycle Science Plan (1999) recognizes the need to expand atmospheric monitoring over terrestrial surfaces and the need to have a stronger characterization of the isotopic composition of CO2 in terrestrial biosphere-atmosphere exchange. In that regard, the Terrestrial Carbon Processes (TCP) Program specifically identifies the need to "... obtain isotopic data that pinpoints source and seasonality of CO2 fluxes". This project directly addresses the isotope ratio needs identified by both the U.S. Carbon Cycle Science Plan and the TCP Program.

4. Quality Assessment:

Measurement values flagged as questionable or bad by the data provider were set to missing, but the Note indicating a problem may remain. Quality assurance of the samples collected manually and by the automated sampling system are discussed in Schauer et al. (2003).

5. Data Acquisition Materials and Methods:

Flasks were collected by an automated sampling system (Schauer et al. 2003) for analyses of concentration, 13C and 18O ratios of carbon dioxide at AmeriFlux sites, including Wind River Canopy Crane Research Facility, Washington, Rannells Flint Hills Prairie, Kansas, Harvard Forest, Massachusetts, and Howland Forest, Maine.

Flasks were analyzed for isotope ratios at the Stable Isotope Ratio Facility for Environmental Research (SIRFER) at the University of Utah using a continuous-flow isotope ratio mass spectrometer system (Precon attached to a Delta S, San Jose, CA). Concentrations of carbon dioxide were measured with a bellow/IRGA system (Bowling et al. 2001). Beginning in April 2004, both concentration and isotope ratios were measured by an automated GC-IRMS system (Schauer et al. 2004).

Site with Supplemental Information

TCP site names cross referenced to FLUXNET site names and linked to FLUXNET web site with supplemental information.

TCP Site TCP Location FLUX_site_name IGBP_class Latitude Longitude Elev State FLUX_ network FLUX_site_link
Wind RiverCraneWind River Crane Site Evergreen needleleaf forest 45.8204889 -121.95191 355 WA AmeriFlux http://www.fluxnet.ornl.gov/site/1103
Wind RiverYoung Stand  Evergreen needleleaf forest       WA    
Niwot RidgeEastNiwot Ridge Forest-Colorado  (LTER NWT1) Evergreen needleleaf forest 40.0328778 -105.5464 -999CO AmeriFlux http://www.fluxnet.ornl.gov/site/997
Niwot RidgeWestNiwot Ridge Forest (2)-Colorado  (LTER NWT2) Evergreen needleleaf forest 40.0325 -105.54694 -999CO Unaffiliated http://www.fluxnet.ornl.gov/site/998
Rannells Flint Hills PrairieUngrazed Site Rannells Ranch (ungrazed) Grasslands 39.13900 -96.52300 -999KS Unaffiliated http://www.fluxnet.ornl.gov/site/920
Howland ForestMain TowerHowland Forest Main Tower Mixed forest 45.20407 -68.740278 60ME AmeriFlux http://www.fluxnet.ornl.gov/site/890
Harvard ForestEMS Annex Walk-Up Tower
EMS (130m SW of the eddy flux tower)
Harvard Forest EMS Tower (HFR1) Mixed forest 42.5377556 -72.171478 340MA AmeriFlux http://www.fluxnet.ornl.gov/site/886

6. Data Access:

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC)  [http://daac.ornl.gov].

Data Archive Center:

Contact for Data Center Access Information:

E-mail: uso@daac.ornl.gov
Telephone: +1 (865) 241-3952

7. References:

Bowling DR, Cook CS, Ehleringer JR (2001) Technique to measure CO2 mixing ratio in small flasks with a bellows/IRGA system. Agricultural and Forest Meteorology, 109, 61-65. doi:10.1016/S0168-1923(01)00252-0

CCWG, 1999.  A U.S. Carbon Cycle Science Plan.  Sarmiento, J.L. and S.C. Wofsy (eds.). Carbon and Climate Working Group, University Corporation for Atmospheric Research, Washington, DC, USA, 69 pp.

Lai CT, Schauer AJ, Owensby C, Ham JM, and Ehleringer JR (2003) Isotopic Air Sampling in a Tallgrass Prairie to Partition Net Ecosystem CO2 Exchange, Journal of Geophysical Research, 108, D18(4566), doi:10.1029/2002JD003369.

Lai C-T, Ehleringer JR, Tans PP, Wofsy SC, Urbanski SP, Hollinger DY (2004) Estimating photosynthetic 13C discrimination in terrestrial CO2 exchange from canopy to regional scales, Global Biogeochemical Cycles, 18, GB1041, doi:10.1029/2003GB002148.

Schauer AJ, Lai C-T, Bowling DR, and Ehleringer JR (2003) An automated sampler for collection of atmospheric trace gas samples for stable isotope analyses. Agricultural and Forest Meteorology, 118, 113-124. doi:10.1016/S0168-1923(03)00065-0

Schauer AJ, Cook C, Lott M, Ehleringer JR (2004) An automated system for stable isotope and concentration analyses of CO2 from small atmospheric samples, submitted to Rapid Communications in Mass Spectrometry.