Glacial Refugium of Pinus pumila (Pall.) Regel in Northeastern Siberia

摘要

One of the most glowing representatives of the Kolyma flora, Pinus pumila (Pall.) Regel (Japanese stone pine), is a typical shrub in larch forests of the northern Okhotsk region, basins of the Kolyma and Indigirka rivers, and high-shrub tundra of the Chukchi Peninsula. It also forms a pine belt in mountains above the forest boundary, which gives way to the grass-underbrush mountain tundra and bald mountains. In the southern Chukchi Peninsula, Pinus pumila along with Duschekia fruticosa (Rupr.) Pouzar and Betula middendorffii Trautv. et C. A. Mey form trailing forests transitional between tundra and taiga. Pinus pumila pollen, usually predominating in subfossil spore-and-pollen spectra of northeastern Siberia, is found as single grains or a subordinate component (up 2-3%, rarely 10%) in spectra of lacustrine deposits formed during the last glacial stage (isotope stage 2) in the Preboreal and Boreal times of the Holocene. Sometimes, its content increases to 15-22% in spectra of lacustrine deposits synchronous to the last glacial stage near the northern coast of the Sea of Okhotsk, evidently indicating the proximity of Japanese stone pine thickets.