fulltext - DiVA

Vegetation of coastal Bohusliin 121Fig. 6. With decreasing demand for wood and grazing, closed deciduous wood invades the fissure valleys (Morkedalen,Mollosund, SW. peninsula of Orust Island). Sorbus aucuparia (to the right), Malus silvestris, Alnus glutinosa, etc.,field layer of Vaccinietum molinietosum and Filipenduletum. Sept. 17, 1958. Photo R. Ivar:::son.The brushwood near the coast grows predominantlyon the south-facing slopes. This may be due,in the first place, to the stronger insolation ofthese slopes, and further to their better protectionfrom the northern winds. The top of the substratumusually consists of boulders or shingle which isonly rarely covered with more fine-granular soils.These markedly stony surface layers make the substratumwarm. The supply of water in the deeperparts of bouldery ground is generally good, thisbeing of significance in the dry coastal climate,especially in spring.Salix species, chiefly S. aurita and S. cinerea,dominate another type of brushwood, Salicetumauritae. In addition, Myrica gale and Vacciniumuliginosum are present, often also Rhamnus frangula.The Salicetum scrubs generally settle on aplane substratum in small, wet depressions in therock. They are not dependent on a southwardexposure of the locality (as are the Prunetumscrubs), and may occu.r even m sites stronglyexposed to the wind.The most common field layer vegetation in thebrushwood is formed by Vaccinietum myrtilli,the subunion deschampsietosum (IVARSSON 1962,p. 100), which consists of Deschampsia flexuosa,Dryopteris filix-mas, Lonicera periclymenum, Rubusidaeus, etc. The substratum is, as a rule, dry andthe soil deposit thin. In strong wind exposure, oron very thin soil, V accinium myrtillus is replacedas dominant by Deschampsia flexuosa. Vaccinietummyrtilli deschampsietosum is not confined to thescrub, occurring also outside it on boulder ground.In another subunion, Vaccinietum myrtilli molinietosum,M olinia coerulea is present, with Corn ussuecica, Potentilla erecta, Trientalis europaea, andothers. It grows on grounds with a high subsoil waterlevel and is related to the wet heaths (see above).The substratum, which is often bouldery, is coveredwith a thick layer of peaty humus.Acta PhytogeogT. Suec. 50