Pm. Anderson et Lb. Brubaker, VEGETATION HISTORY OF NORTHCENTRAL ALASKA - A MAPPED SUMMARY OF LATE-QUATERNARY POLLEN DATA, Quaternary science reviews, 13(1), 1994, pp. 71-92
Fossil pollen data, as illustrated by isopoll and isochrone maps, docu
ment the complex late Quaternary history of tundra and boreal forest d
evelopment in northcentral Alaska. Major plant taxa behaved independen
tly over time, resulting in substantial differences in the vegetation
history of eastern and western regions. Major vegetation changes are i
n general agreement with GCM simulations and confirm the importance of
the continental ice sheet and insolation variations in determining la
te Quaternary climatic trends. Herb-dominated tundra characterized the
vegetation between 18 and 14 ka BP, with mesic graminoid tundra in lo
wer elevations of western areas and more xeric, sparse tundra communit
ies in the east and at higher elevations. Moist Betula tussock tundra
rapidly replaced the western herb tundra ca. 14 ka BP. However, Betula
shrubs expanded more slowly in the east, establishing relatively dry
shrub tundra as the predominant regional vegetation by ca. 12 ka BP. R
iver valleys and south-facing slopes supported Populus woodlands betwe
en 11 and 9 ka BP, but shrub tundra continued to dominate most upland
sites. Alnus shrubs first expanded in the southwestern Brooks Range be
tween 10 and 9 ka BP, spreading rapidly throughout the entire region b
etween 8 and 7 ka BP. Picea glauca populations also expanded between 1
0 and 9 ka BP, but from source areas in northwestern Canada. The P. gl
auca forests were most abundant in riparian settings, but isolated sta
nds probably also established in the shrub tundra. P. glauca reached t
he central Brooks Range by ca. 8 ka BP, followed by an apparent popula
tion decline between 8 and 7 ka BP. P. mariana became the dominant tre
e species ca. 6 ka BP, when it invaded non-riparian P. glauca forests
in eastern and central areas and moist shrub tussock tundra in the wes
t. The modern distribution of communities in northcentral Alaska was a
chieved between 6 and 4 ka BP.