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Glimpses of the Bothnian CoastBy ERIK SKYEThe coast of N orrland, extending from the mouthof the river Dalalven in the south to that of theTorne ·river in the north is about 800 km long. Itruns along the Gulf of Bothnia, which is dividedinto a northern part, the Bothnian Bay (Bottenviken),separated from the southern Bothnian Sea(Bottenhavet) by the straits of Norra Kvarken (seeWlERN's and PEKKARI's contributions). Regardingvegetation and flora this coast diverges markedlyfrom the rest of the Swedish coastline.The:-coastal strip is governed by a comparativelymaritime local climate (ANGSTROM 1958) amongwhose distinguishing traits is the late spring. Mayand June are cool and rather dry, and most of therainfall and a good deal of fog occur in the heightof the fairly warm summer. Compared to conditionsin the interior the autumn is mild, but winteris often severe and rather continent.al in character,due to the fact that most of the Bothnian Bay andNorra Kvarken are usually icebound. The centralpart of the Bothnian Sea freezes only in very hardwinters. The frequency of gales is considerablyhigher during the winter half year, and velocities aregreater, too. The violent storms often come fromthe north or north-east.The forests of the Bothnian coast of Sweden havebeen heavily exploited for several centuries, firstfor the production of tar, during the last hundredyears or so for timber and paper pulp. Around 1900the sawmill industry reached its peak. The timberit used was still mostly of large dimensions, beingderived from old stands. Sawn timber was a greatarticle of export. In many places along the coastand as far up the river systems as floating waspossible whole forests were often simply eradicatedand forestry in the modern sense of the word couldhardly be said to exist. Often dwarfed or crippledtrees were left behind to reproduce themselves ingaps and clearings. It has been asserted that thisnegative selection at least in pine has gone onfor so long that the present-day stands along thecoast have a worse genotype than those in theinterior (LINDQUIST & RuNQUIST 1943).Gales affect the coast at all seasons, but the worstdamage is done in winter when the coastal forestsare ravaged periodically by snow storms so heavythat large areas are cleared of trees. Unless theground is already frozen these blizzards may havea devastating effect ( OsTMAN 1922 and 1955). Thespruce is regarded as more exposed than the pine,but in certain years even the latter succumbs,especially in recently thinned-out stands. Since thedeciduous trees are generally bare when thesestorms descend, they are as a rule completelyspared. For this reason the untouched coastalforest usually has an element of deciduous trees,especially Betula verrucosa, B. pubescens, Populustremula or Salix caprea.A further important factor in the life-cycle of thecoastal forest is fire. Various parts of our coasthave been ravaged by fires, usually accidentallystarted by man, and there are cases of extensiveforests being burnt down in this way (HoGBOM1934). The first tree to appear on the burnt landis usually the birch, especially Betula verrucosa.Only later do the conifers move in again. There aremany reasons for this, chiefly the slower growthof conifer seedlings (spruce being slower than pinein this respect) and the severe drought at thebeginning of the vegetation period. Only when thebirch has reached a sufficient height to keep theground from drying out and the blanket of deadbirch leaves is beginning to fill the gaps betweenboulders, replacing the humus that was completelyActa Phytogeogr. Suec. 50