The history and geobotanical position of the Icelandic flora
Löve, Áskell; Löve, Doris
A Tertiary landbridge created by volcanism on the North Atlantic rift incorporated areas that became cemented into Iceland during the Pliocene-Pleistocene. The first vegetation on this land seems to have been the warm-temperate nemoral forest, remnants of which are presently met with mainly in eastern Asia and eastern North America. It dispersed southeastward, later followed by the American conifer forest vegetation; when even that was displaced after Greenland and America were separated, it was replaced by European boreal and later Siberian arctic-alpine plants. Iceland was never completely covered by the Pleistocene glaciations, but the flora was slowly reduced after its isolation, from several thousand mainly temperate plants to about 400 species of mainly cryophytes. Very few additions came by aid of oceanic currents, first from the Pacific when the Bering Straits opened in the Pliocene, and then during or after the glaciations from North America and perhaps Siberia. The present strictly native vascular flora is known to encompass 412 biological species, to which may perhaps be added a few still unobserved cryophytes to be expected because of their general distribution and half a score taxa reported by visitors during the past two centuries but never again collected, perhaps because of infrequent flowering typical of plants of cold and hot deserts. We have no idea of how many, if any, species may have become extinct in historical times during which about half of the area covered with vegetation eleven centuries ago has eroded away, but there is no reason to believe that they have been even a handful. There are no endemic species. Of several hundred aliens occasionally observed less than 110 seem to be able to reproduce in normal years, whereas only 30 species of the latter have become integrated into the natural vegetation. The Icelandic flora consists almost exclusively of cryophytes of which about 40 % reach the high-arctic zone. The climate is oceanic and cool, but not cold, and windy with a high chilling effect. The landscape and vegetation are arctic, belonging to the Lapponic province of the Circumarctic region of Meusel and to the lowarctic zone as defined by others.