120 HUGO SJORS 



and Sweden, due to the broken topography. The wide occurrence of Tilia in 

 Finland makes it broader there. 



The Main Boreal sub-zone corresponds, in Sweden, both to the upper part 

 of the area where Myrica gale still occurs, and to the central Norrland or 

 middle sub-region which lacks Myrica and a number of other southern 

 species. The nearest Finnish equivalent is the sub-region of Ostrobottnia 

 (Pohjanmaa), according to Kalela (1958, 1961). It borders the central Taiga 

 towards the east, but seems to be somewhat more northern in latitudinal 

 position. 



In northern Sweden, open pine-lichen woodlands of Sub-Arctic type are 

 closely confined to coarse, sandy and gravelly soils, and thus do not form a 

 regionally characteristic feature. According to Ahti (1961), they occur also on 

 other soils in northernmost Finland, but lichen woodlands are not so wide- 

 spread as in more continental parts of the Sub-Arctic areas. However, even 

 forests of a more mesic appearance tend to be widely spaced in northern and 

 high upland parts of Boreal Fennoscandia. The spacing of the forest ought to 

 be used as a phytogeographical regional criterion. Its importance in Swedish 

 forestry has only recently been duly emphasized (Ebeling, 1962). Stature and 

 rate of growth have long been considered important for site classification 

 (edaphical as well as climatic). 



Thus the uppermost and northernmost coniferous woodlands in Fenno- 

 scandia are of Sub-Arctic type with regard to the wide spacing, slow growth 

 and low stature of the conifers. In Sweden, the "Pre-Alpine conifer forest 

 sub-region" (sensu Du Rietz, 1950, p. 7; Swedish = fjdllbarrskogsregionen, 

 Du Rietz, 1942b, 1952 or "upper sub-region of the northern coniferous 

 forest region", Sjors, 1950, p. 177; 1956, p. 202) is largely identical with the 

 area above the economic limit for artificial regeneration (Swedish = skogs- 

 odlingsgrdnsen) in the State forests of Sweden, as drawn by Hojer (1954). 

 It seems likely that some more areas in the high uplands (outside the 

 mountainous district proper) should be included in the area equivalent to the 

 Sub-Arctic, with respect to the poor growth of the forest. Du Rietz (1952, p. 7) 

 gives the lower limit at about 350 m in the north and 600 m in Harjedalen. 

 In Finland, according to Ahti (1961), both the coniferous woodland area of 

 Lappland and that of "Perapohjola" (farther south; terms by Kalela, 1958) 

 as well as some of the birchwoods (see below) belong in the Sub-Arctic (or 

 northern Taiga) sub-zone. 



Practically everywhere in Fennoscandia (also the Russian parts, i.e. iCola 

 Peninsula), birchwoods {Betula pubescens ssp. tortuosa) extend beyond the 

 limit of coniferous trees. The vertical extension of this zone, which is com- 

 monly regarded as Sub-Alpine, is very variable, from almost none to several 

 hundred meters, a fact showing that it is hardly a zone of equal significance in 

 all parts. If a Woodland-tundra sub-zone exists in Fennoscandia, it is located 

 in the upper part of the birch belt (and near the Polar coast) where birches 



