LATE QUATERNARY VEGETATIONAL HISTORY OF GRAYS LAKE, IDAHO

Pollen contained in sediment cores, from Grays Lake, Idaho, indicate cold, dry conditions from almost-equal-to 70 000 to 30 000 yr BP when an Artemisia steppe surrounded Grays Lake and extended into the nearby mountains. From almost-equal-to 30 000 until 11 500 yr BP, somewhat moister conditions supported a conifer woodland. Pinus and other conifers grew in the foothills and among Artemisia on the open plains. Increases in Picea, Abies, and Artemisia signaled the onset of a cool transitional climate almost-equal-to 11 500 yr BP. Juniperus and members of the Chenopodiaceae/Amaranthaceae and Compositae families all became more abundant as the climate became warmer and drier. Xeric conditions persisted from almost-equal-to 10 000 to 7100 yr BP, reaching a maximum almost-equal-to 8200 yr BP. Subsequently, the climate of the Grays Lake Basin has been cooler and moister, with increases in conifers and decreases in Juniperus and steppe plants.