Alaska in the Ice Age: was it bluegrass country? (Paleobiology).

At the height of the last ice age, northern portions of Alaska and the Yukon Territory were covered with an arid yet productive grassland that would have supported an abundance of large grazing mammals, according to a new analysis of fossils from the region.

Botanical species in this ancient ecosystem included sagebrush, bluegrass, sedges, and herbs. That's a combination unlike any on the arctic tundra today, says Charles E. Schweger, a paleoecologist at the University of Alberta in Edmonton.

Previous studies of the region's fossil pollen came up with a similar botanical mix, but some scientists questioned those analyses because pollen grains can waft long distances on the wind. Schweger and his team, who published their findings in the June 5 Nature, analyzed fossilized plant parts from three sites in the Yukon. Some of the specimens came from a 24,000-year-old rodent nest, and others were preserved in a 26,000-year-old peat deposit that also held mammoth remains.

Although average temperatures in the region probably were around 6[degrees]C cooler than today, a dearth of precipitation precluded the formation of large volumes of permafrost, says Schweger. Therefore, he and his coworkers surmise, soil nutrients were more readily available to plants that in turn supported many mammoths, bison, horses, and camels. -S.P.