AMPHI-ATLANTIC ZONATION, NEMORAL TO ARCTIC 121 



are often interspersed by barren areas, and are in any case low and nearly 

 shrubby. 



This uppermost Sub-Alpine sub-zone (or rather "Hemi-Alpine" ecotone 

 because the open patches are outposts of Alpine plant communities) is usually 

 of narrow vertical extension in the Scandes (Scandinavian mountains) proper 

 but is more extensive on the elevated plateaux of northeasternmost Fenno- 

 scandia. This type of vegetation even goes down to sea-level on the Polar 

 coasts of Norway and the Kola Peninsula. 



The lower parts of the birchwoods are continuous with the birches usually 

 of small tree size, reaching as much as 10 m or more in sheltered valleys and 

 slopes with rich, moist soils. These lower parts are better regarded as 

 equivalent to the Sub-Arctic. 



In a recent work Hustich (1960) regards most of northernmost Fenno- 

 scandia, with woodlands formed by birch and some pine, as a Sub-Arctic 

 region which he considers different from the Sub-Alpine region and equivalent 

 to the woodland-tundra farther east. This seems to be an underestimation. In 

 some of his earlier papers (e.g. 1949, p. 52) on Canadian phytogeography, 

 Hustich used the rather ambivalent term "Sub-Arctic" expressly in the 

 meaning "Woodland-tundra". However, in 1957, he included some more 

 "southerly" and even Main Boreal vegetation under the heading of Sub- 

 Arctic. 



The Sub-Alpine -Sub- Arctic birchwoods are a feature of cool, oceanic 

 areas. Outliers of them are found on southwest Greenland and on Iceland. 

 The impact of severe over-grazing has probably caused them to disappear from 

 the Shetland Islands (Spence, 1960), and much of the Scottish Highlands. 

 However, there is no definite evidence that a birch belt has existed above 

 the pinewoods of Scotland, except in the extreme north and west (McVean 

 and Ratcliffe, 1962). Birchwoods are also locally present, usually near 

 river estuaries and deltas, within the Siberian woodland-tundra, where the 

 latter comes close to the Arctic Sea (Lavrenko and Sochava, 1954). Betiila 

 Ermanii birchwoods also grow in Kamchatka and some of the Kuriles 

 together with Sub-Alpine alder thickets. 



ARCTIC AND ALPINE ZONES 



The zonal subdivision of the Arctic is far from clear. It is evident that 

 altitude and maritimity influence Arctic vegetation as much as latitude, 

 and thus regional subdivision cannot result in regularly consecutive zones on 

 a small-scale map except on flat continents or very large islands. Polunin 

 (1951) has proposed a subdivision into three zones (Low Arctic, Middle 

 Arctic, and High Arctic), but it is not known exactly how these zones are 

 distributed. A more detailed subdivision has been carried out and mapped for 



