fulltext - DiVA

120 H. PETER HALLBERG AND REINHOLD IV ARSSONFig. 5. The shell deposits aretypically localized to broken topography,this one, at Gravedal,Tegneby, Orust Island, beingdeposited in a broad cleft betweenrocky hills. The bright shell soil,being partly excavated or troddenby the grazing cattle or horses,is patchily covered by the Anthyllisvulneraria - Alchemilla glaucescensass. The deposit is surroundedby Calluna, and on the bottom ofthe little ravine Alnus glutinosa.July 26, 1958. Photo H. P. Hallberg.tensis, but differs from other pasture-land communities(see above) by the presence of speciessuch as Anthyllis vulneraria, Oarex caryophyllea,Oarlina vulgaris, Oirsium acaule, Plantago media andRanunculus bulbosus. Some species typical ofNardetalia or Molinio-Arrhenatheretalia (TuxEN1937) are represented, including the species of Cynosurion,Oynosurus cristatus, Phleum pratense andTrifolium repens. The lime content and texture ofthe soil, the degree of moistness and the extent ofgrazing are the most important factors in thedevelopment of variants of this association.Along the edges of deciduous woods of Quercus,Oorylus, Ulmus, etc., and the borders of Prunetumscrub, along fences and on slopes, a marginal communitygrows on shell deposits in the interior coastland.It is closely related to Geranietum, thoughlacking Geranium sanguineum and some otherconstituents of the latter association.WETLAND COMMUNITIES.-0n wet ground containingshell deposits, a tussocky vegetation hasoften been formed. The tussocks are capped byfragments of moist meadow and separated by fen .The whole vegetation is generally referable to Lepidocarpion(W ALDHEIM, unpublished; Du RrETZ1961 b, p. 21), earlier called Euscorpidion (DuRrETZ 1949a, p. '294). Oarex lepidocarpa is very rarein Bohuslan. In northern Bohuslan, the allianceis characterized by several other plants, also rarein this area, e.g. Oarex capillaris, Herminiummonorchis, Parnassia palustris and Selaginella selaginoides.Between the .tussocks dominate differentspecies of Drepanocladus, Scorpidium scorpioides,or Nostoc sp. The tussocks belong to Cariceto­Ctenidietum (cf. ALBERTSON 1946a, p. ll7), beingdominated by Oarex dioeca, C. flacca, Eriophorumlatifolium, Festuca ovina, Oampylium stellatum, Otenidiummolluscum, and others. As the tussocksgrow sufficiently high, species like Oalluna, Ericatetralix, etc., invade. When grazing is discontinued,the Cariceto-Ctenidietum is overgrown by Alnusglutinosa forest (see below), sometimes prceded bySalix-Betula scrub. In the northernmost part ofthe archipelago, also Pinus silvestris appears.Woody vegetationBRUSHWOOD OR SCRUB.-Prunus spinosa growseven far westwards, and on sheltered shores it mayeven invade the lines of floatsam. The plants thatnormally frequent decaying seaweed drift appearbetween the bushes, without being affected by theirpresence. The compact thickets, Prunetum spinosae,include, apart from Prunus spinosa, also Orataegusspp., Rosa spp., Rhamnus cathartica, Rh. frangulaand Viburnum opulus. In northern Bohuslan Ribesspicatum and Ligustrum vulgare occur in addition,while Orataegus oxyacantha decreases northwards.Acta Phytogeogr. Suec. 50