Arctic LTER Database

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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 

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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 via LTER Data Poral
Dataset ID:2003-2009gscurveparameters.08
Dataset Title:Best fit parameters describing net CO2 flux light response curves measured during the ITEX CO2 flux survey 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
Zip Code:02543
Investigator 2: 
First Name:Mark
Last Name:van Wijk
Address line 2:
Address line 3:
Zip Code:
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
Address line 2:
Address line 3:
Zip Code:
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:carbon dioxide fluxes, light response curves, normalized difference vegetation index, primary production
Abstract:Ecosystem CO2 flux light response curves were measured on 1m x 1m plots ( some 0.3m x 0.3m plots in 2006 and some 0.7m x0.7m plots in 2009) across the arctic. This file contains the best fit parameters that describe these light response curves, together with corresponding NDVI data for each curve. 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
Online URL:
Data File URL
Data File Name 2003-2009gscurveparameters.dat
Beginning Date 7/5/2003
End Date 8/17/2009
Number of Data Records 446
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 curve parameters. Inserted new column for ôplot sizeö because 2006 data include measurements made on 0.3m x 0.3m plots. Changed time format for all data to e.g. 1124 not 11:24. 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.
Version 6: Updated metadata form to newer version (without site sheet). Missing values changed to #N/A. CH 25Jan2013 Updated to newer metadata with site sheet. CH March 2013.
Version 7 Changed Time to text since it has text code in it. Jim L 16May13
Version 8: Corrected Distrubution URL. It had xlsfiles in the path. Jim L 19Jun14
RESEARCH LOCATION:                    
Location Name LTER Moist Acidic Tussock Tundra Imnavait Creek Stepps site Paddus Latnjajaure Adventdalen Zackenberg research area zone 1a Barrow 2304 Tower  
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 (74║28ĺ N, 20║34ĺ 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 68.9966666666667  
Longitude -149.61058 -149.31 18.85 18.85 18.5 15.6333333333333 -19.4333333333333 -156.6 -150.2125  
Elevation 750 884 In Meters In Meters In Meters In Meters In Meters In Meters    
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  
Organisms studied
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 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 2009: Data was collected on five 0.7m x 0.7m flux plots along a burn severity gradient in mid-June 2009.

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

We measured net CO2 flux using a Licor 6400 photosynthesis system (Li-Cor Inc., Lincoln, Nebraska, USA) connected to a plexiglass chamber. For most sites, the chamber measured 1m x 1m x 0.25m, but a 0.3 x 0.3 x 0.15m was used in 2006 and a 0.7 x 0.7 x 0.25m was used in 2009 due to limited accessibility at these sites. In Alaska in late season 2004 and at Zackenberg from 25th July 2006 onwards, we used a LiCor 6200 photosynthesis system. Flux data from the LiCor 6200 were corrected for the effects of water vapor build-up according to Hooper et al 2002.

At each plot 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 and used 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 concentrations in the chamber being recorded by the Licor every 2-3 secs. Incident radiation, average temperature and NDVI were also measured on each plot for each light curve.

A saturating (Michaelis-Menton type) function is fitted to the measured data. Best fit parameters describing each light curve are calculated by minimizing the sum of squared errors between measured and modeled NEP values.

In 2003, all flux data from a plot on one day are grouped into one light curve.

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 (Unispec only at Stepps site phase 2)
Abisko and Svalbard: Unispec and Skye sensor (Unispec only during June at Abisko)
Zackenberg: 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. The end of the fiber optic was kept approximately 1m 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.

The light response curve is modeled as a rectangular hyperbola:

NEP = Re - [(Pmax*PAR)/(K + PAR)]

where Re = ecosystem respiration [Ámol C m-2 ground s-1]
Pmax = theoretical light saturated photosynthesis [Ámol C m-2 ground s-1]
K = half saturation constant [Ámol PAR m-2 ground s-1]

The initial slope of the light response curve (light use efficiency or E0) and the light compensation point (LCP) are calculated from these parameters as:

E0 = (Pmax/K)

LCP = (RE*K)/(Pmax-RE)

where Re = ecosystem respiration [Ámol C m-2 ground s-1]
Pmax = theoretical light saturated photosynthesis [Ámol C m-2 ground s-1]
K = half saturation constant [Ámol PAR m-2 ground s-1]
E0 = ecosystem light use efficiency [Ámol C Ámol-1 PAR]
LCP = ecosystem light compensation point [Ámol PAR m-2 ground s-1]


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

COMMENTS: all times are given as local times. Sorting variables and curve ID numbers match the flux data from which the curve is calculated, in the ITEX CO2 flux data file 2003-2009gsflux.dat

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

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 132:1ľ11

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.


Data Table

Variable Name Variable Description Data Type Units DateTime Format Code Information Missing Value Code
YEAR Year measurement taken datetime   YYYY    
DATE Date measurement taken datetime   DD-MMM-YY    
SITE Abisko, Imnavait, Toolik, Svalbard, Zackenberg, AR Burn or Barrow text        
GROUP Location of flux plots at each site text        
PLOT Individual plot identifier text        
TREAT Control or fertilised with N and P fertiliser text        
PHASE Measurement series (round of measurement within each year) text        
PLOT SIZE Plot size of 1m x 1m or 0.3m x 0.3m or 0.7 x 0.7m text        
CURVE ID Light curve identifier text        
TIME time the light curve was taken (avg indicates a combination of more than one curve in a day) text        
NDVI NDVI of flux plot number dimensionless     #N/A=Missing or Not Measured
Pmax light saturated photosynthesis parameter number micromolePerMeterSquaredPerSecond     #N/A=Missing or Not Measured
K half saturation constant number micromolePerMeterSquaredPerSecond     #N/A=Missing or Not Measured
Re ecosystem respiration number micromolePerMeterSquaredPerSecond     #N/A=Missing or Not Measured
Eo ecosystem initial light use efficiency number micromolePerMicromole     #N/A=Missing or Not Measured
LCP ecosystem light compensation point number micromolePerMeterSquaredPerSecond     #N/A=Missing or Not Measured
AIRTEMP average air temperature number celsius     #N/A=Missing or Not Measured
MAX PAR The maximum average PAR value under which a flux measurement is recorded for that curve. number micromolePerMeterSquaredPerSecond     #N/A=Missing or Not Measured
Comments explaination of why the curve lacks parameter values text