Circumpolar Arctic Vegetation Map
Vegetation
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Circumpolar Arctic Vegetation Map, Vegetation Units
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Area of Map Units
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Relationship between map units, soil moisture, and climate
Mapped polygons at 1:7.5 million scale contain many vegetation types. The map often portrays the dominant zonal vegetation within each mapped polygon. Zonal sites are areas where the vegetation develops under the prevailing climate, uninfluenced by extremes of soil moisture, snow, soil chemistry, or disturbance, and are generally flat or gently sloping, moderately drained sites, with fine-grained soils (Vysotsky 1927). Large areas of azonal vegetation that are dependent on specific soil or hydrological conditions, such as mountain ranges and large wetlands, were also mapped.
The legend contains five broad physiognomic categories:
- B — barrens
- G — graminoid-dominated tundras
- P — prostrate-shrub-dominated tundras
- S — erect-shrub-dominated tundras
- W — wetlands
These are subdivided into 15 vegetation mapping units with numeric codes added to the alphabetic codes. The mapping units are named according to dominant plant functional types except in the mountains where complexes of vegetation are named according to the dominant bedrock (carbonate and noncarbonate mountain complexes). The coloring scheme of the map is suggestive of the physiognomy of the vegetation. The units can also be arranged along axes of the bioclimate gradient and soil moisture (see Fig App. 2.1). The plant functional types are based on a variety of criteria including growth form (e.g., graminoids, shrubs), size (e.g., dwarf and low shrubs), and taxonomical status (e.g., sedges, rushes, grasses). The legend takes into special consideration the stature of woody shrubs, which is a major diagnostic feature of zonal vegetation in the Arctic (Edlund and Alt 1989, Walker et al. 2002, Yurtsev 1994b).
Very steep bioclimate gradients occur in mountains, so these areas are mapped as complexes of elevation belts (see Fig. App. 2.2). Mountainous areas of the map are shown with hachures; the background color indicates the nature of the bedrock, and the color of the hachures indicate the bioclimate subzone at the base of the mountains.
Fig. App. 2.2. Color scheme for elevation belts in mountainous areas. Mountain complexes were mapped using a diagonal hachure pattern. The background color indicates the nature of the bedrock (magenta for noncarbonate rocks, blue-purple for carbonate bedrock), and the color of the hachures indicate the bioclimate subzone at the base of the mountains (purple, Subzone A; blue, Subzone B; green, Subzone C; yellow, Subzone D; and red, Subzone E). The code numbers in mountainous areas have an additional small alphabetic suffix that indicates the subzone at the base of the mountains. For example, carbonate mountains (map code B4) in Subzone E have a small e added to the (map code B4e). Mountains in subzone E could have up to six elevation belts (if the mountains are high enough). The lowest belt, Belt e is dominated by low-shrub tundra (S2); the next higher belt, Belt d has erect dwarf-shrub tundra (S1); Belt c has prostrate dwarf-shrub, herb tundra (P1); Belt b has rush/grass, forb, cryptogam tundra (G1); Belt a has cryptogam, herb barrens (B1); and the nival belt is snow and ice covered. The belts are 333 m intervals, which correspond about a 2 °C to a decrease in the mean July temperature or about –6 °C per 1000 m elevation as predicted by the ecological adiabatic lapse rate (Barry & Chorely 1987). Since only one elevational belt can be represented on each polygon, the color of the lowest belt is used for the polygon although higher elevational belts may exist in that polygon. (CAVM Team 2003, with permission of USFWS).
- Barrens
- Graminoid Tundras
- Prostrate-shrub tundras
- Erect-shrub tundras
- Wetlands