fulltext - DiVA

The Borderland169'Fig. 2. The same area of Sweden asin Fig. 1 with the southern limitof the Norrland terrain. To thefauna and flora the permanencyof snow is an important ecologicalfactor, especially in the borderlandin question. The southernlimits of the areas of more than100, 120 and 140 days with permanentsnow cover are schematicallydelineated (ace. to Atlasover Sverige). Orily north of theborderland snow cover typicallylasts until early spring; the dottedarea marks occurrence of snow onMarch 31, 1948. By M. Fries.other hand, below the border, wide areas are coveredby clayey water sediments whereas above itwater sediments are coarser, usually sandy or, atthe most, silty, clay being absent almost entirely;they also are much less extensive, except in thebroad valleys. The scarceness of clayey materialmakes the soils less fertile (on an average), and, inparticular, reduces the trophic level of the freshwaters;it seems likely that this factor is equallyresponsible as the climatic difference for the markeddivergence in the composition of the aquatic vegetation.Soil development is largely different on each sideof the border. Mor formation and podsolization areby far more predominant above it, but on theother hand, fairly good flushed soils are also common.The valleys, particularly the wide valley ofthe DaHilven River, are in many respects differentboth from the lowland and the uplands: sandy tosilty soils prevail, podsolization is weak, mires arerare and deep ravines and numerous hillsides formhabitats not met with in the lowland.The distribution of lime is another complication.Near the east coast the clays and tills are more orless calcareous, but only below the borderline.Many southern plants reach their northern limitsin this area. Farther west, calcareous soils are nowhereextensively distributed, but there are scatteredlocal outcrops of marble (Archaean limestone),the latter being most numerous above the border.At some distance farther north, one finds both calcareousareas (near Lake Siljan) and extremelybase-poor areas (western part of Dalarna, etc.). Thedistribution of calciphytes in a strict sense thusdoes not show the general pattern, except perhapswhen climate is a more decisive factor than calcareoussoil (e.g. for Carex .flacca).The agricultural differences have been mentioned.Much of the lowland plain belongs to largefarms or even estates; the fields are wide and mainlyused for grains, largely wheat or barley. North ofthe border, nearly all farms are small, farming isconcentrated to the valleys, and the chief cropsare hay, barley and oats although nowadays also.Acta Phytogeog.r. Suec. 50