5 research outputs found
Recommended from our members
Glacial Refugium of Pinus pumila (Pall.) Regel in Northeastern Siberia
One of the most glowing representatives of the Kolyma flora [1], ''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 [2]. 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 [3], evidently indicating the proximity of Japanese stone pine thickets
Recommended from our members
Paleoclimatic implications of glacial and postglacial refugia for Pinus pumila in western Beringia
Palynological results from Julietta Lake currently provide the most direct evidence to support the existence of a glacial refugium for Pinus pumila in mountains of southwestern Beringia. Both percentages and accumulation rates indicate the evergreen shrub survived until at least {approx}19,000 14C yr B.P. in the Upper Kolyma region. Percentage data suggest numbers dwindled into the late glaciation, whereas pollen accumulation rates point towards a more rapid demise shortly after {approx}19,000 14C yr B.P. Pinus pumila did not re-establish in any great numbers until {approx}8100 14C yr B.P., despite the local presence {approx}9800 14C yr B.P. of Larix dahurica, which shares similar summer temperature requirements. The postglacial thermal maximum (in Beringia {approx}11,000-9000 14C yr B.P.) provided Pinus pumila shrubs with equally harsh albeit different conditions for survival than those present during the LGM. Regional records indicate that in this time of maximum warmth Pinus pumila likely sheltered in a second, lower-elevation refugium. Paleoclimatic models and modern ecology suggest that shifts in the nature of seasonal transitions and not only seasonal extremes have played important roles in the history of Pinus pumila over the last {approx}21,000 14C yr B.P
Recommended from our members
First Data on Lake Level Changes in Northeastern Siberia during the Postglacial Time
Moraines of the Tyellakh Group [1] (QIII{sub 2-4}) preserved in river valleys of the northeastern Kolyma River basin indicate development of cirque-valley glaciers originating in the Kilgan Mountains located at the northeastern periphery of the Kolyma Ridge that separates drainage basins of the Sea of Okhotsk and Kolyma River. Moraines host lakes with a length of up to 1-5 km and a relatively small width depending on the valley bottom dimension. The study of lacustrine sediments, their bed-by-bed palynological analysis, and radiocarbon dating provided the first information on lake levels during the final glacial stage of the Late Pleistocene, as well as the Pleistocene-Holocene boundary and Holocene, for the upper reaches of the Kolyma River