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72 OLOF RUNEin flushed sites, e.g. along brooks, whereas Populustremula, usually crippled, is occasionally seen indrier places.Among the lowland plants still abundant in thesubalpine belt but seldom exceeding the timberline,a number of plants of mires or moist woodlandmay be mentioned: Oarex flava, 0. lasiocarpa, 0.loliacea, 0. pauciflora, 0. media, Eriophorum latifolium,Angelica silvestris, Pedicularis palustris var.borealis. Though not a mire plant, Luzula pilosashould also be mentioned in this connection.To a great extent the same floristic and vegetationalpatterns appear in the subalpine belt as inthe conifer belt. Thus, plants centered in theScandes such as Aconitum septentrionale, Lactucaalpina and others occur together with southernmadow plants, as mentioned in the section on theconifer belt, but the number of alpine plants increasesin the subalpine belt. Nearly all low-alpineplants descend into the subalpine belt, most frequentlyperhaps Viola biflora.In this connection only a very brief descriptionof the main types of the subalpine woods of Swedencan be given, mainly according to Du RrETZ ( 1942 b).I. HEATH BrRCHwooD being distinguished by afield layer dominated by dwarf shrubs. It occurson dry to mesic, more or less acid soils and occupiesmost of the subalpine belt. It can be divided into:(1) Heath birchwood with lichens characterizedby a bottom layer mainly of Oladonia and similarlichens. This type of low, open wood covers vastareas in the very dry continental districts in thenorth-eastern parts of the mountain areas. (It alsoappears in the dry areas of northernmost Dalarnaand south-western Harjedalen.) (2) Heath birchwoodwith mosses which is the most importantbirchwood type and can be divided into severalsubordinate groups. On windy ridges, almost bareblownin winter, it appears as a crowberry birchwood(a), the field layer dominated by the northernEmpetrum hermaphroditum. The most commonfacies, the bilberry birchwood (b), occurs in moresheltered places protected by a snow cover duringthe winter. It is dominated by Vaccinium myrtillustogether with Deschampsia flexuosa, in thehumid west, or on somewhat moister soil, alsoActa Phytogeogr. Sttec. 50Oornus suecica. On slightly less acid soil it changesinto oak-fern-bilberry birchwood (c) with the smallfern Gymnocarpium (Lastrea) dryopteris. In nearlyall types of bilberry birchwood such herbs asSolidago virgaurea, M elampyrum pratense, M.silvaticum and Potentilla erecta are more or lessfrequent. On moister and only slightly acid soilalso Geranium silvaticum, Trollius europaeus, Gnaphaliumnorvegicum, Viola biflora and others aremore or less abundant (d). This type of birchforest is more frequent in the western parts of themountains. It may be classified as meadow-heathbirchwood or bilberry birchwood with low herbs.II. MEADow BIRCHWooD being distinguished bya lush field layer of broad-leaved, mainly tallherbs, grasses and ferns, practically without dwarfshrubs. The bottom layer is dominated by otherspecies of mosses than in the heath forest. Meadowbirchwoods occur on slopes with a flush of mobileground water and with much snow during thewinter, usually on somewhat calcareous, neutralto slightly acid soils presumably rich in availablenitrogen.The meadow birchwoods represent two maintypes: (1) Meadow birchwood with tall herbs andgrasses. In the field layer prevail such herbs asAconitum septentrionale, Lactuca alpina, Filipendulaulmaria, Geranium silvaticum, Trollius europaeus,Myosotis silvatica ssp. frigida, Polygonatum verticillatum,grasses such as Milium effusum andOalamagrostis purpurea and ferns such as Athyriumfilix-femina and Matteuccia struthiopteris. A bushlayer with, e.g., Prunus padus var. borealis andRibes spicatum ssp. lapponicum may sometimesoccur. (2) Meadow birchwood with tall ferns. Inthe field layer large ferns prevail .more or lesscompletely, such as Athyrium filix-femina, Dryopterisdilatata and M atteuccia struthiopteris. As abush layer Alnus incana var .. virescens sometimesoccurs. This type of meadow birch forest occurs onvery well watered slopes and is most common inthe oceanic subregion of the subalpine belt.In a southern exposure where the snow thawsearly the meadow birchwoods, especially that ofthe tall-fern type, in places display a vernal aspectwith early flowering plants such as Corydalis