Circumpolar Arctic Bioclimate Subzone A

 

Subzone A. Isachsen, Ellef Ringnes Island, Canada. Photo D.A. Walker.
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Circumpolar Arctic Bioclimate Subzone A
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Subzone A Description

Subzone A includes mostly fog-shrouded islands within the permanent arctic ice pack where July mean temperatures are less than about 2-3 °C, such as Ellef Ringnes, Amund Ringnes, King Christian, northern Prince Patrick and nearby islands in the northwest corner of the Canadian Archipelago. It also includes the coastal fringe of northernmost Greenland and northern Ellesmere and northern Axel Heiberg Islands, the northeastern portion of Svalbard, Franz Josef Land, Severnaya Zemlya, the northern tips of the Taimyr Peninsula, and northern tip of Novaya Zemlya. The summer temperatures in these areas are near freezing all summer due to a combination of nearly continuous cloud and fog cover, which limits solar radiation, and the close proximity to the ice-covered ocean (Bay 1997, Razzhivin 1999). More continental inland areas of the larger islands are often considerably warmer. Permanent ice covers large areas of the land. Major parts of the nonglacial land surfaces are largely barren, often with <5% cover of vascular plants, however, meadow-like plant communities are not uncommon on mesic fine-grained soils, where there is sufficient moisture provided by the cold humid oceanic climate.

Woody plants are absent on zonal sites. Zonal sites are flat or gently sloping, moderately drained sites with fine-grained soils that are not influenced by extremes of soil moisture, snow, soil chemistry, or disturbance and which fully express the influence of the prevailing regional climate. Lichens, bryophytes, cyanobacteria, and scattered forbs (e.g., Papaver, Draba, Saxifraga, and Stellaria) are the dominant plants. Many of the forbs, lichens and mosses have a compact cushion growth form. In midsummer, the arctic poppy, Papaver radicatum, is the most conspicuous plant over large portions of this subzone. Other important low-growing cushion-forb genera include Draba, Saxifraga, Minuartia, and Cerastium. Soil lichens, mosses, and liverworts can cover a high percentage of the surface, particularly in more maritime areas such as Novaya Zemlya (Alexandrova 1980). Rushes (Luzula and Juncus) and grasses (Alopecurus, Puccinellia, Phippsia, and Dupontia) are the main graminoid groups. Sedges are rare, and wetlands lack organic peat layers. There is little contrast in the composition of vegetation on mesic sites, streamside sites, and snowbeds. The vascular-plant flora is extremely depauperate, consisting of only about 50-60 species (Young 1971). On fine grained soils, the extremely cold temperatures and the thin sparse plant canopy induce intense frost activity, which forms networks of small (<50 cm diameter) nonsorted hummocks and polygons, and plants are confined mainly to the depressions between the hummocks (Chernov and Matveyeva 1997). This subzone has also been called the “herb subzone” (Walker et al. 2002) and the “Papaver dahlianum zone” because of the dominance of herbaceous vascular plant species and the absence of woody plants.