Created: 2014-02-03 13:18:58
Modified: 2015-11-10 10:02:53
DESCRIPTION OF AREA CONTAINING SITE:
U11B 1-ha grid located within the lower part of U11A 1 km grid. Site description: Gentle (1 degree) north facing basin deposit with strangmoor, wetland hummocks, palsas; wet acidic tundra. Vegetation communities: (1) Raised microsites in basin including hummocks and palsas: Wet Carex rotundata, C. rariflora, Betula nana, Salix fuscescens, Sphagnum lenense graminoid, dwarf-shrub tundra. (2) Footslope of west-facing hill: Moist Betula nana, Eriophorum vaginatum, Sphagnum spp. dwarf-shrub, tussock-graminoid tundra. (3) Lower microsites in basin including interhummock areas with standing water: Wet Eriophorum scheuchzeri, Carex rotundata, Sphagnum orientale, Drepanocladus revolvens graminoid tundra. (4) Marginal area of the basin with few shrubs: Wet Carex rotundata, Salix fuscescens, Sphagnum lenense graminoid, moss tundra. (5) Beaded pond of Imnavait Creek: Aquatic Sparganium hyperboreum, Hippuris vulgaris forb marsh. Cover of top 5 species: Sphagnum lenense (13%), Carex rotundata (8%), Sphagnum warnstorfii (7%), Betula nana (6%), Sphagnum orientale (6%).
Mean vegetation height: 2.2 +/- 3.2 cm
Mean live moss layer thickness: 2.0 +/- 1.0 cm
Organic layer thickness: 34 + 1.7 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.
Additional climate snow and hydrologic data are also available at http://www.uaf.edu/water/projects/NorthSlope/imnavait/imnavait.html
CALM USA George Washington University
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