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The re-use of scientific data has the potential to greatly increase communication, collaboration and synthesis within and among disciplines, and thus is fostered, supported and encouraged. Permission to use this dataset is granted to the Data User free of charge subject to the following terms:

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2 ) Redistribution. The data are provided for use by the Data User. The metadata and this license must accompany all copies made and be available to all users of this Data Set. The Data User will not redistribute the original Data Set beyond this collaboration sphere.
3 ) Citation. It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly cite the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set. Citation should take the following general form: Creator, Year of Data Publication, Title of Dataset, Publisher, Dataset identifier. For example:

Shaver, G. 1989. Above ground biomass in acidic tussock tundra experimental site, 1989, Arctic LTER, Toolik, Alaska. Arctic LTER, Marine Biological Lab, Woods Hole, Ma 02543. 1989gsttbm http://ecosystems.mbl.edu/arc/terrest/biomass/index.shtml 

4 ) Acknowledgement. The Data User should acknowledge any institutional support or specific funding awards referenced in the metadata accompanying this dataset in any publications where the Data Set contributed significantly to its content. Acknowledgements should identify the supporting party, the party that received the support, and any identifying information such as grant numbers. For example:

Data sets were provided by the Arctic LTER. This material is based upon work supported by the National Science Foundation under Grants #DEB-981022, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493.

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Dataset URLs:METADATA: HTML, Rich Text, XML(EML compliant)
DATA: Comma Delimited, Excel file with Metadata and data
Dataset ID:2003-2009flux.07
Dataset Title:ITEX circumarctic CO2 flux survey data from Toolik, Alaska; Abisko, Sweden; Svalbard, Norway; Zackenberg, Northeast Greenland; Anaktuvuk River Burn, Alaska and Barrow, Alaska 2003-2009.
Investigator 1: 
First Name:Gus
Last Name:Shaver
Organization:The Ecosystems Center
Address line 2:Marine Biological Laboratory
Address line 3:7 MBL St.
City:Woods Hole
State:MA
Zip Code:2543
Country:USA
Investigator 2: 
First Name:Mark
Last Name:van Wijk
Organization:
Address line 2:
Address line 3:
City:
State:
Zip Code:
Country:
Investigator 3: 
First Name:Lorna
Last Name:Street
Investigator 4: 
First Name:Brooke
Last Name:Kaye
Investigator 5: 
First Name:Jim
Last Name:Laundre
Investigator 6: 
First Name:Mathew
Last Name:Williams
Investigator 7: 
First Name:Cath
Last Name:Thompson
Investigator 8: 
First Name:Carrie
Last Name:McCalley
Investigator 9: 
First Name:Beth
Last Name:Bernhardt
Investigator 10: 
First Name:Bob
Last Name:Douma
Investigator 11: 
First Name:Celine
Last Name:Ronfort
Investigator 12: 
First Name:Kerry
Last Name:Dinsmore
Investigator 13: 
First Name:Robert
Last Name:Bell
Investigator 14: 
First Name:Peter
Last Name:van Buuren
Investigator 15: 
First Name:Craig
Last Name:Menzies
Investigator 16: 
First Name:Jen
Last Name:Peters
Investigator 17: 
First Name:Scott
Last Name:Graham
Associate Investigators:
Keywords:ITEX flux survey, carbon dioxide exchange, light response curves, NDVI, ecosystem respiration, primary productivity
Abstract:Ecosystem CO2 flux light response curves were measured on 1m x 1m plots across the arctic. This file contains the CO2 and H2O flux measurements and NDVI data for each plot. Survey plots were located in the Toolik Lake LTER fertilization experiment in Alaska; at Imnavait Creek, Alaska; at Paddus, Latnjajaure and the Stepps site near Abisko in northern Sweden; at various sites in Adventdalen, Svalbard; in the Zackenberg valley, Northeast Greenland; at BEO near Barrow, Alaska and at the Anaktuvuk River Burn in Alaska. Measurements were made during the growing seasons 2003 to 2009.

For questions about the Metadata and data contact the Investigators.
For information about this web site contact:
Arctic LTER Information Manager
The Ecosystems Center
Marine Biological Lab
7 MBL St
Woods Hole, MA 02543
Phone (508) 289 7496
Email: arc_im@mbl.edu
Online URL: http://ecosystems.mbl.edu/ARC/
DATA FILE INFORMATION:
Data File URL http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-arc.1606&urlTail=terrest/tracegas/data/2003-2009gsflux.csv
Data File Name 2003-2009gsflux.dat
Beginning Date 7/5/2003
End Date 8/17/2009
Number of Data Records 5001
Other Files to Reference
Availability Status type 1
Quality Control Information
Maintenance Description
Log of Changes: Version 1: Checked file and created eml and html files. Feb 2006 Jiml Version 2: Added Zackenberg 2006 flux data and updated metadat.txt with new site description, methods, references, files to reference etc. Added a new identifier column called "plot size" because 2006 data include measurements made on 0.3m x 0.3m plots. Added new column with uncorrected LiCor 6200 flux data from 2006 and 2004. Changed date in file name from 2005 to 2006. Oct 2006 LStreet
Version 3: Added LTERNET Data Access server proxy for Excel and comma delimited data files.
Version 4: Updated LTERNET Data Access server proxy link for Excel and comma delimited data files. Changed from knb to das in url.
Version 5: Added Toolik and Barrow 2009 data. Changed file name from 2006 to 2009. Added comments column.
Version6: Corrected units on: NEPumolCm2s, H2Ofluxmmolm2s,ReumolCm2s, GEPumolCm2s, uncorrected NEP. Were microMolePer mole; should have been micromolePerMeterSquaredPerSecond. Wrong units on PARumolm2s and PARrange shoul dhave been micromolePerMeterSquaredPerSecond. Changed missing values to "." instead of a blank cell. Jim L 5Oct2011
Version 7: Updated eml to version 2.1.0 Jim L 24jan12
 
RESEARCH LOCATION:                    
Location Name Toolik Field Station Imnavait Creek Abisko Stepps Abisko Paddus Abisko Latnjajare Adventdalen Svalbard, Norway Zackenberg Greenland Barrow Alaska Anaktuvuk River Burn  
Geographic Description Toolik Lake (68 degrees 38N, 149 degrees 34W) Imnavait Creek (68 degrees 37N, 149 degrees 18W) Alaska, U.S. "Stepps" site (68 degrees 18N, 18 degrees 51E) near Abisko, Sweden. Paddus (68 degrees 19N, 18 degrees 51E) near Abisko, Sweden. Latnjajaure (68 degrees 21N, 18 degrees 30E) near Abisko, Sweden. Adventdalen (78 degrees 13N, 15 degrees 38E) Svalbard, Norway. Zackenberg research area zone 1a (7428 N, 2034 W), Northeast Greenland. Barrow ( 71 18' N, 156 36' W) Alaska, USA. Anaktuvuk River Burn (68 56-59' N, 150 12-16' W) Alaska, USA.  
Location Bounding Box                    
West Bounding Coordinate                    
East Bounding Coordinate                    
North Bounding Coordinate                    
South Bounding Coordinate                    
OR if single point location                    
Latitude 68.62405 68.6167 68.3 68.3167 68.35 78.2166666666667 74.4666666666667 71.31 68.9  
Longitude -149.61058 -149.31 18.85 18.85 18.5 15.6333333333333 -19.4333333333333 -156.6 -150.2  
Elevation                    
Link to Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map  
                     
 
TAXONOMIC COVERAGE:
Organisms studied
 
Methods:RESEARCH LOCATIONS:
Imnavait Creek, Alaska 2003: Measurements were made on 8 flux plots in different vegetation types along the topographic sequence of the west facing slope of Imnavait Creek catchment. A light response curve was measured on each plot several times during early July and several times during late July/early August.

Imnavait Creek, Alaska 2004: Measurements were made on 15 plots along the topographic sequence of the west facing slope of Imnavait Creek catchment, in the same area as 2003. A light response curve was measured on each plot once in late June/early July and once in August.

Toolik Lake, Alaska 2004. Measurements were made on a total of 20 flux plots in treatment (N +P) and control blocks of the LTER fertilization experiment at Toolik Lake, including the moist acidic tussock, non-acidic tussock, non acidic non-tussock, inlet wet sedge and heath sites. Light curves were measured on each plot once in late June/early July and once in August.

Abisko, Sweden 2004. Measurements were made on 11 plots at the "Stepps" site, each measured once in July and once in August. Measurements were made on 13 plots at Paddus and 12 plots at Latnjajaure, once in July and August.

Abisko, Sweden 2005. 15 plots were located at the "Stepps" site, measurements were made on 3 occasions through June/ early July and once in mid August. During the 3rd phase of measurements in June we conducted a diurnal series on five of the plots, measuring a light curve once every 4 hrs for 28 hrs.

Svalbard 2005. Measurements were made on 41 plots at various sites in Adventdalen, one light curve was measured on each plot during July.

Zackenberg 2006. Data were collected on 35 1 x 1m plots and 25 0.3 x 0.3m plots across a range of vegetation types. 13 of the 0.3 x 0.3m plots were located within 1m x 1m plots (identified by plot name with suffix "b1, b2 or b3"), the remainder were independent of the 1 x 1m plots (B14-25). A light curve was measured on each plot once, all measurements were made from 8 July through 1 Aug 2006.

Toolik, Alaska 2009: Data were collected on nine 1m x 1m flux plots, three in each vegetation type. Vegetation types included moist acidic tundra (MAT), dry heath (HTH) and wet sedge (WSG). Each plot was measured at approximately 2 weeks intervals from mid-June to mid-August 2009.

Anaktuvuk River Burn, Alaska 2009: Data was collected on five 0.7m x 0.7m flux plots along a burn severity gradient during mid-June 2009.

Barrow, Alaska 2009: Data was collected on thirteen 0.7m 0.7m flux plots along a moisture gradient during late-July to early-August 2009.


EXPERIMENTAL DESIGN AND METHODS:
CO2 and H2O fluxes were measured using a Licor 6400 photosynthesis system (Li- Inc., Lincoln, Nebraska, USA) connected to a plexiglass chamber. For most sites, the chamber used measured 1m x 1m x 0.25m. Because of the limited accessibility of some sites, a smaller chamber was occasionally utilized: at Zackenberg in 2006 a 0.3 x 0.3 x 0.15m chamber was used on 25 plots and at Barrow and Anaktuvuk River Burn sites in 2009 a 0.7 x 0.7 x 0.25m chamber was used on a total of 18 plots. In Alaska in late season 2004 we measured CO2 and H2O fluxes using a LiCor 6200 photosynthesis system (note: the Licor 6200 does not measure air pressure, estimates from Toolik weather station data are used, with correction for altitude at Imnavait). We also used a LiCor 6200 at Zackenberg, from 25th July onwards - this instrument was borrowed from Susanne Konig in the Copenhagen University group. Measurements made with 6200 system are corrected for effects of water vapor flux using protocols recommended by Hooper et al. 2002. Uncorrected flux values from the 6200 are also given in a separate column.

We fitted the 1m x 1 m chamber over a square aluminum base supported several centimeters above the ground surface by hollow steel legs driven down to the permafrost. An airtight seal was created between base and chamber by lining adjoining surfaces with rubber gasket. We sealed the base to the tundra by weighting an attached plastic skirt with heavy chains; where possible we pushed the chains firmly down into the moss layer to create a good seal. We screwed the LiCor custom chamber head attachment over holes drilled into the plexiglass chamber, again sealing with rubber gasket. The air in the chamber was mixed using four small fans powered by a 12v battery.

The 0.3m x 0.3m chamber was set up identically to the 1m x 1m chamber, using a smaller aluminum frame. This was also sealed to the ground with a plastic skirt and chain. Often it was possible to make the frame level without using legs. We used only one 12V fan to mix air in the chamber, the chamber head was attached exactly in the same way as for the 1m x 1m chamber.

The 0.7m x 0.7m chamber was set up identically to the 1m x 1m chamber, again using a smaller aluminum frame. This was also sealed to the ground with a plastic skirt and chain. We used four 12V fans to mix air in the chamber and the chamber head was attached exactly in the same way as for the 1m x 1m chamber.

At each plot (all chamber sizes) we took measurements to create a light response curve: 2-3 measurements were made at ambient light conditions, followed by 2 flux measurements at each of 3 successive shading levels, with finally 3 measurements under complete darkness. We shaded the chamber by layering 3 fine mesh net cloths, with a tarpaulin to block all light from the chamber. Flux measurements under complete darkness represent ecosystem respiration. At each light level a flux measurement lasted 45 - 60 secs in total, CO2 and H2O concentrations in the chamber being recorded by the Licor every 2-3 secs. After each measurement we lifted the chamber until CO2 and H2O concentrations had stabilized at ambient levels.

After each light curve we determined chamber volume by taking depth measurements from the top of the chamber base to the ground. For the 1m x 1m base 36 depth measurements were made at regular 20cm intervals by setting a 1m x1m plastic frame with a 20cm x 20cm string grid on top of the base. For the 0.3m x 0.3m chamber 9 depth measurements were taken, one at each corner, one at the mid point of each side, and one in the middle of the plot. For the 0.7m x 0.7m chamber, a string grid with smaller intervals was utilized. The volume determined by these depth measurements (chamber surface area*average depth) was added to the volume of the chamber itself. The surface area of the inside of the 1 m x 1 m chamber was 0.89m2. In 2009, the surface area of the inside of the chamber was 0.8836m2 for 1m bases and 0.4096m2 for all 0.7m bases.

For 2003-2006 data, NEP is usually calculated from the first 15-20secs of measurement. Where the data is scattered due to very small net changes in CO2 over time, the entire period of 45-60secs is used. If light levels change during a measurement only periods where the light is constant is used to calculate the flux. Often under shade or darkness the first few seconds of data are discarded as the CO2 concentration change over time is non linear, representing adaptation of the system to new conditions. For 2009 data, NEP is calculated from the entire measurement period. When abnormalities in CO2 slope were observed due to leaks or changes in light levels, certain portions of the measurement were discarded. CO2 slope was always taken from contiguous data points (i.e. points were never removed from the middle of the measurement period). Often under shade or darkness the first few seconds of data are discarded as the CO2 concentration change over time is non linear, representing adaptation of the system to new conditions.

For 2003-2006 data, H2O flux is also usually calculated from the first 15-20secs of the measurement period. However, where CO2 flux was calculated over the entire 60sec period, water flux is also calculated over the entire period. This should be considered as the build up of water vapor in the chamber almost always followed a curve which began to plateau towards the end of the 60secs. For a more reliable measure of evapotranspiration see water fluxes calculated at time t=0secs see 2003-2004waterflux.xls.
For 2009 data, H2O flux is calculated over the same time window as CO2. Further QC of H2O data would be beneficial before use as H20 over time is nonlinear in many cases. Also, H20 fluxes from nighttime diurnal measurements are suspect.

We measured NDVI on each flux plot using either a portable 2 channel field sensor (Skye Instruments) or Unispec spectral analyzer (PP Systems) or both:

Toolik 2003: Skye sensor
Toolik 2004: Unispec and Skye sensor
Abisko 2004: Unispec and Skye sensor (except Stepps site phase 2)
Abisko and Svalbard 2005: Unispec and Skye sensor (except June at Abisko)
Zackenberg 2006: Unispec
Toolik 2009: Unispec
Barrow 2009: Unispec

The unispec spectral analyzer measures reflected light intensity in 256 portions of the visible spectrum from ~300nm to ~1100nm. A foreoptic cable transmits light reflected from the target to the instrument, a measurement scan lasts for ~10ms. 9 scans were measured in a regular grid for each of the flux plots. In 2003-2006 measurements, the end of the fiber optic was kept 80 cm vertically above the ground surface resulting in a view of the vegetation of approx. 20cm diameter. In 2009 measurements, the end of the fiber optic was kept 1 m vertically above the ground surface resulting in a view of the vegetation of approx. 20cm diameter. For the 0.3m x 0.3m plots, 3 scans were taken from directly above the plot with a field of view of approximately 30cm diameter. The average of these three scans was then taken. Incident radiation was measured using a reference standard in order that reflectance from the vegetation could be calculated as a percentage of incoming solar radiation

The program Multispec5.1.5.exe was used to compile Unispec reflectance spectra from the raw target spectra.

The skye NDVI sensor measures total radiation reflected from the vegetation (without measuring incident radiation) in the wavebands 570nm-680nm and 725nm - 1100nm. NDVI is then calculated as below.

CALCULATIONS:
Fluxes are calculated from the slope of chamber CO2 (umol mol-1) [or H2O (mmol mol-1)] concentration against time.


NEP = (rho * vol * dC/dt)/ SA rho = (P_av * 1000)/(R* T)


where NEP = net CO2 flux [umol m-2 s-1]
rho = air density [mol/m3]
P_av = pressure [kPa]
R = ideal gas constant 8.314 [J mol K-1]
T = temperature [K] = Temp_av [0c] + 273.
vol = chamber volume [m3]
dC/dt = slope of chamber CO2 conc against time [umol mol-1 s-1]
SA = chamber surface area [m2] = 1

RE = NEP during dark measurement
GEP = RE - NEP

NDVI = (RII-RI)/ (RI + RII)

where RI = average reflectance from 570nm to 680nm
RII = average reflectance from 725nm to 1000nm.

COMMENTS: All times are given as local times. Shade level was not recorded in 2003. A negative net flux indicates uptake of carbon by the vegetation, a positive net flux indicates loss of carbon from vegetation to the atmosphere. Re and GEP are both given as positive numbers. Air temperature values from the 6400 were measured using a thermistor located inside the chamber head air space. Air temperature using the 6200 was measured using a thermocouple attached to the chamber head, and inserted inside the flux chamber.

FOR MORE INFORMATION CONTACT: Gus Shaver, The Ecosystems Center, Woods Hole, MA, 02543, USA

REFERENCE CITATIONS:
Douma, J.C., van Wijk, M.T., Lang, S.I., Shaver, G.R. (2007) The contribution of mosses to the carbon and water exchange of artic ecosystems: quantification and relationships with system properties. Plant, Cell and Environment 30: 1205-1215.

Hooper D.U., Cardon Z. G., Chapin III F. S. Durant, M. (2002) Corrected calculations for soil and ecosystem measurements of CO2 flux using the LI-COR 6200 portable photosynthesis system. Oecologia 132:111.

Shaver, G.R., Street, L.E., Rastetter, E.B., van Wijk, M.T., Williams, M. (2007) Functional convergence in regulation of net CO2 flux in heterogeneous tundra landscapes in Alaska and Sweden. Journal of Ecology 95:802-817.

Street, L.E., Shaver, G.R., Williams, M., van Wijk, M.T. (2007) What is the relationship between changes in canopy leaf area and changes in photosynthetic CO2 flux in arctic ecosystems? Journal of Ecology 95: 139-150.

Williams, M., Street, L.E., van Wijk, M.T., and Shaver, G.R. (2006) Identifying Differences in Carbon Exchange among Arctic Ecosystem Types. Ecosystems 9:288-304.

FORMAT OF DATA FILE: ASCII

NUMBER OF RECORDS: 5001

Data Table

Variable Name Variable Description Data Type Units DateTime Format Code Information Missing Value Code
YEAR Year measurement taken datetime   YYYY   .=Missing or Not Measured
DATE Date measurement taken datetime   DD-MMM-YY   .=Missing or Not Measured
SITE Abisko, Toolik, Svalbard, Zackenberg, AR Burn or Barrow text       .=Missing or Not Measured
GROUP Location of flux plots at each site text       .=Missing or Not Measured
PLOT Individual plot identifier text       .=Missing or Not Measured
TREAT Control or fertilised with N and P fertiliser text       .=Missing or Not Measured
PHASE Measurement series (round of measurement within each year) text       .=Missing or Not Measured
PLOT SIZE Plot size of 1m x 1m or 0.3m x 0.3m or 0.7 x 0.7m text       .=Missing or Not Measured
curve ID Light curve identifier text       .=Missing or Not Measured
OBSNUM Individual flux measurement identifier text       .=Missing or Not Measured
STARTTIME Start time of flux measurement in local time. datetime   hh:mm:ss   .=Missing or Not Measured
SHADELEVEL L=ambient light, S1=one shade cloth, S2=2 cloths, S3=3 cloths, D= dark text       .=Missing or Not Measured
PRESSUREkPa Barometric pressure number kilopascal     .=Missing or Not Measured
AIRTEMPC Air temperature number celsius     .=Missing or Not Measured
CO2ppm Average chamber CO2 concentration during measurment number partPerMillion     .=Missing or Not Measured
H2O Average chamber H2O concentration during measurment number millimolePerMole     .=Missing or Not Measured
PARumolm2s Incident photosynthetic active radiation number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
PARrange PAR range during flux measurement number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
NDVI Normalised difference vegetation index number dimensionless     .=Missing or Not Measured
NEPumolCm2s Net ecosystem productivity number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
H2Ofluxmmolm2s H20 flux number millimolePerMeterSquaredPerSecond     .=Missing or Not Measured
ReumolCm2s Ecosystem respiration number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
GEPumolCm2s Gross ecosystem productivity number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
uncorrected NEP Uncorrected Licor 6200 net CO2 flux number micromolePerMeterSquaredPerSecond     .=Missing or Not Measured
comments Notes about data text       .=Missing or Not Measured
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