Borovichev E.A. Botanical excursion on the Northern Soroya. Hammerfest, 2014.

Wind-pollinated birchflowers are collected in drooping catkins. Birch pollen grains are produced in huge quantities and are resistant to decomposition processes , that s why they arefossilized, both in peat and lake sediments. Judgingfrom thesefossil records birch advanced to the north o fFennoscandia about 6-7 ОООyears ago, succeedingperiglacial tundra after glacier retreat Birch forests Soraya Island lies on the border of the polar submaritime zones everywhere in Fennoscandia, tree-line. Birch forests o f the island, like those are evidently characteristic for regions with forming the subalpine, subarctic and Mountain ash (Sorbus aucuparia subsp. glabrata) is a shrubby tree under these conditions. It hasfragrant flowers and sour-bitterfruits, which are an important food resourcefor many birds oceanic cool climates. On the other side o f the World, the Pacific coast o f Sakhalin, the Kamchatka peninsula, and some Japanese islands have a corresponding ecological zone with another birch species, Betula ermanii. On S 0 r 0 ya the upper limit of birch is at a lower altitude than in more southern and more continental areas o f Norway, They are often situated in sheltered river valleys and on terraces under steep mountain slopes. The dominant tree of this forest is Mountain Birch (Betula pubescens ssp. czerepanovii). Birch is highly adapted to this timber-line environment. It has very variable shape; polycormic trees (with several trunks starting from one point) are usually crooked, or twisted at the basal part owing to heavy snow-pressure and snow-creep and seldom higher than few meters. In sheltered 28