RESEARCH LOCATIONS:
Imnavait Creek, Alaska 2003: Measurements were made on 8 1m x 1m flux plots in different vegetation types along the topographic sequence of the west facing slope of Imnavait Creek catchment.

Imnavait Creek, Alaska 2004: Measurements were made on 15 1m x 1m plots along the topographic sequence of the west facing slope of Imnavait Creek catchment, in the same area as 2003.

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.

Abisko, Sweden 2004: 11 plots were located at the Stepps site, 13 plots at Paddus and 12 plots at Latnjajaure in a range of vegetation types.

Abisko, Sweden 2005: Measurements were made on 15 plots at the Stepps site.

Svalbard 2005: Measurements were made on 41 plots at various sites in Adventdalen.

Zackenberg 2006: Measurements were made on 35 1m x 1m plots and 25 0.3m x 0.3m plots at various sites within 2km of the ZERO research station - in research zone 1a.

Toolik 2009: Data were collected on nine 1m x 1m 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 plots along a burn severity gradient during mid-June 2009.

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

EXPERIMENTAL DESIGN AND METHODS:
We measured soil characteristics every time CO2 flux measurements were made on a plot. Sorting variables correspond to those in other ITEX flux survey files. The following data are available at the following sites:

Toolik 2003 - thaw depth
Toolik 2004 - thaw depth, VWC, soil temperature at 5cm
Abisko 2004 - VWC, soil temperature at 5cm and 10cm
Abisko 2005 - VWC, soil temperature at 5cm and 10cm
Svalbard 2005 - VWC, soil temperature at 5cm and 10cm
Zackenberg 2006 - VWC, soil temperature at 5cm and 10cm
Toolik 2009- Surface temp, VWC, soil temperature at 5cm and 10cm, depth of thaw for some plots only
Barrow 2009- Surface temp, VWC, soil temperature at 5cm and 10cm, depth of thaw for some plots only
AR Burn 2009- Surface temp, VWC, soil temperature at 5cm and 10cm

We measured soil temperature at 5cm and 10cm below the soil surface 5 times per plot (3 times for 0.3m x 0.3m plots), using traceable soil temperature probes (Fischer Scientific). Where possible we also took 5 soil VWC (%) measurements (1-3 for 0.3m x 0.3m plots) and 5 thaw depth measurements. VWC was measured using a Hydrosense Water Content Sensor (TDR probe) with 20cm tines (Campbell Scientific). The TDR probe was inserted into the soil to the full depth of 20cm whenever possible. If not the tines were inserted at an angle; the approximate depth reached is indicated in the notes column.

We measured thaw depth using a graduated steel rod pushed down through the soil to the top of the permafrost. At times it was evident from the abruptness of change in penetrability that it was rock and not permafrost underlying the thawed soil, this is indicated in the notes column. If the soil was too rocky to penetrate to take temperature measurements this is also indicated in the notes column.

Calculations:
The TDR probe is calibrated at manufacture for use in agricultural soils; for tundra soils meter readings were corrected using the equation:

actual VWC (%) = 0.5952*(meter reading) + 7.684
R2 = 0.8649

(J Powers, unpublished data, 2003)

COMMENTS:

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

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

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

See Methods