fulltext - DiVA

2 16 JIM LUNDQVISTthe valleys are slopes where the bedrock was washedfree from loose deposits, whereas the more lowlyingparts of the valleys are occupied by sediments.Arable fields cover only 0.3 % of Lappland butthere are many small farms in the valleys, in theeast and south of Lappland also on the till-coveredforested ridges.Mter the end of the latest glaciation there was awarm and dry epoch, and also, as mentioned, thelevel of the country was lower. There is reason tobelieve that many plants with fairly high heatdemands were then spread along the valleys.The present less favourable climate of the innerparts of Lappland is characterized by relativelywarm but short summers (in July 12 to 15°0) andlong cold winters (in January -ll to -14°0).The winters are even colder than in the mountains.Even though this is definitely a continental climate,it is much milder than is to be expected with regardto the latitude (p. 8). The period with a meantemperature above + 4 °0 is generally shorter than140 days, and the actual growth period about fourmonths only.The precipitation is generally low and onlyoccasionally reaches annual values of 600 mm, inthe south of Lappland. In the far north-north-eastwe find values lower than 400 mm. The precipitationrises from a minimum in April-May to amaximum in late summer and autumn; more ofthe precipitation falls as rain than as snow. Theground is covered with snow for 5-! months in thesouth and for 7 months in the north but the snowcover is much thicker in the south than in thenorth-north-east. The lakes as a rule break up inMay-June and freeze again in October-November.See further, ATLAS OVER SvERIGE, sheets 25-40,and A GEOGRAPHY OF NoRDEN (1960).SouTH-FACING HILLs AND MouNTAINSBy Jim LundqvistThe flora and vegetation of south-facing hills andmountains have for a long time stimulated theinterest of phytogegraphers not only in Swedenbut also in other countries. LINNJEUS in his FloraLapponica (1737) noticed the group of plants which"are in the southern parts of Sweden very commonbut . become highly rare towards the north" (transl.).WAHLENBERG (1812 pp. XXXVIII ff.) discussedthe geographical factors which cause a great numberof species to vanish towards the north. Follow-.ing these pioneers many botanists have enthusiasticallydescribed the flora below the high southfacingcliffs and have given these "gardens" of theflora of Lappland a good reputation (see, e.g.,BJORNSTROM 1856, MELANDER 1881, NYMAN 1895 a,1895 b, AMINOFF 1905, G. ANDERSSON & BIRGER1912, FRODIN 1915, TENGWALL 1925, GRAPEN­GIESSER 1934, SCHIOLER 1934, WISTRAND 1934,1962, G. BJORKMAN 1939, GAUNITZ 1939, DEGELIUS1945 a, HALDEN 1950, 1956, SELANDER 1950 a, DuRIETZ 1954a, JrM LUNDQVIST 1961). In mostcountries at northern latitudes these ecosystemsare characterized by special habitat conditionsreflected by a multitude of vegetation types all ofwhich contain a markedly high percentage ofthermophilous plants, rare elsewhere in the region.In Central Europe south-facing slopes are evenmore favoured thermally than in Scandinavia, andthere occur species adapted to the hot and drysteppe climate of south-east Europe (Pontic-Sarmatianspecies, cf. KUBITZ 1962, NIEMANN 1962).In northern Europe the plants and plant communitiesin similar sites are called "southern" becausetheir main area of distribution is usually situatedto the south, mostly in low-lying parts of thecountries. Thus Lappland in the north of Swedenhas many cliffs with · a flora, several members ofwhich we do not normally find on level groundexcept at some degrees of latitude farther south.A striking example of this (p. 69) is the elm, Ulmusglabra ssp. montana, which can be found in some ofthese mountains in southern Lappland and Jamt-Acta Phytogeog1·. Stec. 50