Lavrentiya

Created: 2014-01-24 14:05:29
Modified: 2014-01-24 14:07:16

SITE DESCRIPTION

The Lavrentiya site (R27) was initiated in 2000 near the settlement of Lavrentiya, on the Bering Strait coast (65°36' N, 171°03' W). The site’s low, gently sloping (5–10°) ridges and hills, interspersed with stream valleys and small shallow lakes, are characteristic of post-glacial relief in this area. The distinguishing physiographic features are the low hilly relief formed through erosion of Mesozoic block structures by glacial, fluvial and marine processes. The CALM sample grid is located on a gentle mountain slope with northeast exposure (3°N and 1°E) at 70 m a.s.l. between a low massif and a marine terrace. Microrelief on the Gleyic-Histic Cryosol soils is poorly developed. The predominant plant communities are wet sedge Salix mossy tundra. At the peak of vegetative growth the projective cover on the CALM grid of Salix species averaged 32%, sedges 35%, other vascular species 6%, mosses (including Sphagnum spp.) 66%, and lichens 3%.

The local climate and atmospheric motion are highly seasonal and have a strong maritime influence. Strong offshore winds bring cool and cloudy weather and frequent fogs during the warm season. The oceanic climate has high humidity and a small range of diurnal and monthly air temperatures. The closest permanent weather station is at the settlement of Uelen (66°10' N, 169°50' W). Long-term observations at Uelen yield a mean annual air temperature of –7.8°C, and mean monthly temperatures of +5.3°C and –20.3°C for the warmest (July) and coldest (February) months, respectively.  In general, summer temperatures are considerably lower than in the Anadyr’ region, whereas winter air temperatures are higher, resulting in similar annual averages. Due to the severe climate conditions, the area is part of the continuous permafrost zone. Permafrost occurs throughout the area to depths of 200–400 m, and has average annual temperatures of –5 to –7°% at a depth of 12 m (Zamolodchikov et al., 2004).

SAMPLING DESIGN AND METHOD:

1-ha grid consists of a square array of surveyed permanent stakes separated by 10 m, yielding an 11 × 11 array of sampling nodes on each grid. Thaw depth and snow sampling was conducted twice by manual probing at each stake. The two values for each sampling point are averaged, yielding a maximum of 121 data points per grid per probing date. The active layer was not measured at locations where grid points intersect rocks or deep water.