Created: 2014-02-03 13:11:11
Modified: 2014-02-03 13:15:36
DESCRIPTION OF AREA CONTAINING SITE:
U11C 1-ha grid located within middle part of the U11A 1-km grid. It occupies Lower hilislope (15 degrees west-facing) above U11B 1-ha grid.
Site description: Lower hilislope (15 degrees west-facing) with water tracks, scattered glacial erratics and nonsorted circles, moist acidic tundra, shrublands in water tracks. Vegetation communities: Inter-water-track areas: (1) Moist Eriophorum vaginatum, Ledum decumbens, Vaccinium vitis-idaea, Sphagnum girgensohnii tussock-graminoid, dwarf-shrub tundra. (2) Water tracks: Wet Salix pulchra, Rubus chamaemorus, Sphagnum angustifolium low-shrub tundra, and moist Betula nana, Rubus chamaemorus, Sphagnum spp. dwarf-shrub tundra. Cover of top 5 species: Eriophorum vaginatum (12%), Betula nana (11%), Vaccinium vitis-idaea (9%), Carex bigelowii (8%), Ledum decumbens (6%).
Mean vegetation height: 3.6 +/- 3.6 cm
Mean live moss layer thickness: 2.5 +/- 1.1 cm
Organic layer thickness: 15 + 1.9 cm.
(Walker and Bockheim, 1995)
SAMPLING DESIGN AND METHOD:
Beginning in 1995, the active layer has been probed at least annually at the site. The procedure involves pushing a metal rod, calibrated in cm, to the point of refusal, interpreted in most cases to be the frost table. Thaw depth measurements at each site were obtained by probing at 5 m intervals along the plot’s two perpendicular and one diagonal transect, resulting in 71 points per plot per probing date.
In 1995 the site was instrumented with several OnsetTM portable data loggers connected to probe-type thermistors. Each logger/thermistor system has an effective temperature range of -50oC to +33oC and resolution of approximately 0.32oC. At each site, one thermistor was placed in a radiation shield approximately 2 m above the ground surface, and nine loggers were placed at the interface between mineral soil and organic material in various microtopographic positions within the site. Temperature measurements were collected at, 1 hr, and 2 hr intervals depending on season, and year. Details on methodology are provided in Klene et. al 2001.
CALM USA George Washington University
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