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Forest regions 53Fig. 5. Oakwood (Quercus robu1·)with an understorey of Tilia cordataand Corylus. Vernal aspectwith Anemone nemm·osa. The smallhill Linnebjar, Scdra Sandby, inagricultural S Sklme. May 15, 1955.Photo G. & H. Weimarck. Courtesyof the Skime Ass. for Prot. ofNature.(they make up about 5/6 of the standing timber andproduce about 4/5 of the annual increment) butalso by the presence of practically all both unpretentiousand demanding broad-leaved trees ofthe adjacent part of the Nemoral zone; only Acercampestre and Tilia platyphyllos are absent andOarpinus is limited in the Boreo-nemoral to itssouthernmost fringe.NEMORAL TREES.-Beech is fairly common assmall stands, frequently growing near lakes, in thesouthern and south-western parts (the beechspruceforest area of LrNDQUIST 1950 and 1959),and has scattered occurrences farther north, inGotaland only (LrNDQUIST 1931, 1959, HJELMQVIST1940). A southern elm, Ulmusminor ( = carpinifolia),grows on bland and Gotland but nowhere on themainland, and also an eastern elm, U. laevis, hasan isolated area on Oland. Wych elm ( U. glabra)as well as ash, maple (Acer platanoides), smallleavedlime (Tilia cordata), and Sorbus intermedia(endemic to the Baltic area) occur all over theregion and even reach some distance into the trueBoreal zone. Of the oaks, Quercus petraea is nearlyconfined to the south-western parts, and Q. roburoccurs throughout the region but no farther north.As Q. robur is especially -conspicuous, the regionis by Du RmTz (1950 e, 1952, 1964) designated"the (southern) conifer forest region with oak"but the attribute about oak is frequently droppedfor the sake of brevity (e.g. SJORS 1950b, 1956).The mentioned comparatively warmth-demandingtree species, known to the Swedes as "noble",grow scattered or in small groves, and only rarelyform true forests in this region. Their competitiverelations to each other, to other broad -leaved treesand to the spruce, and the dependence of theseconditions on human influence, are extremelycomplicated. In any case, the concept "mixed oakforest" (lying behind the pollen analysts' QM, i.e.Quercetum mixtum) is hardly in accordance withreality, except as a transitory state. On the contraryeach species shows its own peculiar synecologicalbe ha vi our.Mixed broad-leaved stands can be formed,provided that spruce competition and grazing aremoderate when the stand is young. Later elm orash will continue their reproduction and ultimatelytake the lead provided the soil is good enough,for ash and elm are highly dependent on good soils,preferably calcareous; the former is more resistantto excessive moisture; the latter seems frequentlyActa Phytogeog.r. Suec. 50