Created: 2014-02-03 13:02:19
Modified: 2014-02-03 13:05:39
DESCRIPTION OF AREA CONTAINING SITE:
U12B 1-ha grid located within the lower part of U12A 1-km grid. Site description: Gentle (3 degrees) north-facing slope, including water track and nonsorted circles ; moist acidic tundra and water-track complex. Vegetation communities: (1) Tussock tundra areas between nonsorted circles: Moist Eriophorum vaginatum, Betula nana, Hylocomium splendens tussock-graminoid, dwarf-shrub tundra. (2) Vegetatated non sorted circles: Dry Vaccinium vitis-idaea, Racomitrium lanuginosum, Cladina arbuscula prostrate-shrub, fruticos-lichen tundra. (3) Barren nonsorted circles: Dry Luzula arctica, Juncus, Antheliajuratzkana barren. (4) Water tracks: Wet Salix pulchra, Eriophorum angustifolium low-shrub tundra. (5) Shrubby water-track margins: Moist Betula nana, Rubus chamaemorus, Sphagnum girgohnsohnii dwarf-shrub tundra. (6) Water-track transitions: Wet Salix pulchra, Rubus chamaemorus, Sphagnum sp. dwarf-shrub tundra. Cover of topS species: Eriophorum vaginatum (16%), Vaccinium vitis-idaea (12%), Betula nana (10%), Hylocomium splendens (9%), Ledum decumbens (7%).
Mean vegetation height: 5.8 +/- 7.7 cm
Mean live moss layer thickness: 1.8 +/- 1.0 cm
Organic layer thickness: 15 + 1.0 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 the 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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