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Forest regions 61pine districts, there is a large area where spruceis strongly predominant at higher levels. In manyparts of northern Sweden, pine prevails in thevalleys, with their drier climate and coarser soils,and spruce on the hillsides and upland, with amoister climate, excessive snow and above all, morefine-grained material in the tills. At low elevationthere were originally also spruce forests on _finegrainedsedimentary deposits, but these sedimentshave usually been cultivated.. Mixed stands are most common in the coastalareas, mainly in subregions (l) and (2). There hasbeen a great influence from grazing and developmentof mown hay-meadows and from shiftingcultivation, usually in the form of burn-beatingfor crops or grass (ARNBORG 1949, SJORS 1954, pp.8-21, with literature cited) . Tar production tooka heavy toll chiefly from the coastal forests, andin the mining area in the southern part of subregions(l) and (2), the high demand for fuel andcharcoal resulted in much devastation of the forestsculminating in a period 300 to lOO years ago . Littlecan now be seen of this, but much of the mixing ofthe species and the unevenness of the presentstands are due to historical causes, probably alsoto some extent the occurrence of soils of mull typeand under-vegetation rich in herbs (cf. A. SAMUELS­SON 1960).Further inland, the great forest fires of the past(see HoGBOM 1934, Trn:EN 1937 and UGGLA 1958for literature, discussion and botanical data onregeneration) have had a considerable influence ontree distribution, favouring pine as the morefire-resistant and the more rapidly colonizingspecies. Old pines with fire-scars are often seen,being survivors from one or several fires, and nowsurrounded by younger forest. Even in old sprucestands (first or second generation of spruce) onefinds occasional very old pines; they may be remnantsof the first colonists on the burnt area.Special reference is made to ,the work by SIREN(1955) on developmental changes in old stands innorthern Finland. But in many areas the largerpines have been systematically cut out for sawtimber.This "selective cutting", abandoned onlya few decades ago, was a devastating practicewhich left the forest with glades that because ofFig. 11. A remnant of an older generation, this probablyover 400 years old pine stands among poor spruce of thesecond generation. Despite much light and space in theuneven stand, the third generation of birch and pine issuppressed, probably because of lack of nutrition. Thinhumus, dry soil, on which pine would have been predominantif the site had burnt. Stuor Tjatek, MuddusNational Park. July 8, 1947. Photo H. Sjors.root-competition from surrounding inferior treesdid not become reoccupied.Among the numerous works on site and habitatconditions, etc., in North Swedish forests, referencecan only be made to a few, in addition to those citedelsewhere, e.g. HESSELMAN (1926, 1928, 1937),HESSELMAN & M. LUNDQVIST (1935), 0. TAMM(1920, 1931, 1940, 1950), 0. TAMM & WADMAN (1945),WRETLIND ( 1934, 1935), GRANLUND & WENNER­HOLM (1935), RoMELL (1939), E. BJ6RKMAN (1942),ARNBORG (1943b), MA.LMSTROM (1949, 1963),TROEDSSON (1955), C. 0. TAMM (1959), C. 0. TAMM &CARBONNIER (1961). In this as well as otherrespects, Swedish forestry scientists are much in-Acta Phytogeog1·. Suec. 50