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70OLOF RUNEoccurrences of even more exclusive inhabitants ofthe conifer forest region have been found in thesesubalpine areas, viz. Pinguicula villosa, Eleocharispalustris and Carex laxa. It seems probable thatthe suboceanic conditions have a more altitudedepressinginfluence on the coniferous tree layerthan on the other parts of the vegetation.Fig. 4. View of Tarnaby, Lycksele Lappmark, showingoutpost stands of spruce in the birchwood on the southfacingslopes of Mt. Laxfjallet. Lake Gautajaure at mediumwaters. Alpine areas in the background. Photo Lars Bergstrom.phorum brachyantherum, Lycopodium complanatum,Gnaphalium silvaticum, Pinguicula villosa, Rosamajalis, Salix myrtilloides, Carex livida.Several plants restricted to the conifer belt inthe eastern mountains occur in the lower parts ofthe subalpine belt further west, i.e. their upperlimits do not slope so much towards the west asdoes the conifer forest limit. Such species are e.g.,M aianthemum bifolium, Oxalis acetosella, Listeracordata, Drosera anglica, D. rotundifolia, Carexpauciflora, Cirsium palustre, Pyrola rotundifolia(sens. str.), Salix pentandra, Populus tremula (as atree). These plants are thus frequently found evenin the western parts of the deep valleys of southernLappland, being in the subalpine belt though thealtitude is only about 500 m. Sparse and isolatedThe subalpine belt or Regia subalpinaThe birchwood belt extends between the coniferforest limit and the alpine woodless lands. It isalso named the subalpine belt or regio subalpina.In the eastern mountains where the conifer forestlimit is at a high altitude, the subalpine belt appearscomparatively narrow. In this part of the mountainsisolated stands of spruce reproducing themselvesvegetatively by rooting branches also diminish thedominance of the mountain birch. In the valleystraversing the interior of the mountain range thebirch belt covers considerable areas, the upper limitof the birchwood being less lowered towards thewest than that of the conifer forest.The upper limit of the birch belt has been definedin somewhat different ways by various Swedishphytogeographers. TH. C. E. FRIES (1917) andT. A. TENGWALL (1920) established the limit at theuppermost groves of birches, H. SMITH (1920) atthe uppermost birch tree and F. ENQUIST (1933)at the uppermost birch plant irrespective of its size(cf. KILANDER's paper). The definition most commonlyused is that of FRIES and TENGWALL. Likethe other vegetational limits the upper limit of thebirchwood is at a lower altitude in the north thanin the south and in the western suboceanic partsthan in the eastern, more continental, but it seemsto be raised in the high-mountainous areas ascompared to tracts of low mountains. Although thecause of the latter effect has been much discussedthe question is still unsolved. An overlooked explanationis that the small populations of ssp.tortuosa on the sides of low mountains could be lesshardy, being more mixed with lowland Betulapubescens than the populations inhabiting thevalleys of high-mountainous districts and therecomparatively isolated from the pollen and diasporesof the birches of the lowland.The highest birchwoods in northern LapplandActa Phytogeog1-. Suec. 50