Sampling Description:

Starting in 1990, thaw depth has been measured in a small watershed (Tussock watershed, TW) containing an intermittent stream just south of Toolik Lake.  Measurements are made at least twice during the summer season, and surveys are consistently made each year on 2 July and 11 August  (plus or minus 1 day).  The UTM grid (stakes are in a grid at every 100 meters) are used to locate the starting points, and a tape measure is used to mark points every 25 m in between the UTM stakes.  The  thaw sampling grid covers the gently sloping watershed of moist, non-acidic tussock tundra vegetation dominated by Eriophorum vaginatum.  At each of 96 sites on the grid a ruled stainless steel rod was inserted in non-tussock microhabitat (that is, not on top of a tussock but in the inter-tussock space between tussocks) until the frozen layer was reached, and the distance was measured to the top of the upper soil organic mat (beneath the uppermost moss layer if present).  Two measurement were made at each point from 1990-1999, and three measurements were made at each point from 2000 on.  Measurements are made at each site (point on the grid) within a 100 cm radius of each location point on the grid.   The measurements for all sites on the grid are averaged to arrive at a single number (plus error) for each date in each year.

Field and Lab Methods and Protocols

http://arc-lter.ecosystems.mbl.edu/landwater/lw_protocols