Late Quaternary Vegetation History of Northern North America Based on Pollen, Macrofossil, and Faunal Remains*

Abstract

<jats:title>Abstract</jats:title><jats:p>Biome maps spanning the interval from the last glacial maximum to modern times are presented. The biome distributions at 18 ka BP were probably as nearly in equilibrium with climate as are the modern distributions, but deglacial biomes were probably in disequilibrium. Ice sheet configuration was a strong control of climate until 7 ka BP. Regional climate trends can be inferred from changing biome distributions, but during periods of disequilibrium, biome distributions under-represent summer warming. Because of summer cooling by 2-4 °C during the Holocene, largely in the last 3-5 ka, middle and certain early Holocene biome distributions and species compositions are reasonable analogues of future equilibrium displacements due to equivalent warming, at least in areas that were long-since deglaciated. Past biome migration rates in response to rapid regional warming during deglaciation were mainly in the range of 100-200 m per year. If these rates pertain in the future, biomes may shift 10-20 km in most regions over the next century. A major impediment to using former Holocene conditions as a guide to future conditions is that warmer Holocene summers were accompanied by colder winters, whereas warmer future summers will be accompanied by warmer winters.</jats:p>

Bison phylogeography constrains dispersal and viability of the Ice Free Corridor in western Canada

“…Clade 2b is geographically isolated to the region of the postglacial corridor and includes a skull recovered from Banff National Park that dates to ∼305-430 cal y BP (Dataset S1). This increased phylogeographic clustering during postglacial times, compared with before the LGM, probably reflects a trend toward physical isolation of bison populations as open habitats were largely replaced by spruce forest and increasing paludification across northwestern Canada (30).…”

“…First, the opening of the postglacial corridor may have favored south to north, rather than north to south dispersal. Detailed biome reconstructions indicate that southern and central portions of the deglaciating corridor in this time range featured potentially more productive grasslands, open spruce woodlands, and boreal parkland, whereas northern portions of the corridor were marked by alpine, herb, and shrub tundras (30). Southward dispersal may also have been limited for biological reasons, for example, if southern bison were better adapted than northern bison to the expanding grasslands within the corridor region (27).…”

Underwater faunal assemblages: radiocarbon dates and late Quaternary vertebrates from Cold Lake, Alberta and Saskatchewan, Canada

“…Reconstructions of Laurentide ice sheet recession and subsequent landscape revegetation indicate 637 habitable landscapes in the vicinity of Cold Lake by 11,000 yr BP (approximately 13,000 Cal yr BP), 638 with the ice persisting in portions of far northeastern Alberta (Dyke 2005). Pollen records and 639 radiocarbon data from Moore Lake suggest the possibility of habitable landscapes even earlier (Hickman 640 and Schweger 1996).…”

The pattern and style of deglaciation at the Late Wisconsinan Laurentide and Cordilleran ice sheet limits in northeastern British Columbia

“…2C-2E). Over this time frame, unglaciated terrain and unconsolidated deposits exposed by ice retreat and lake drainage were reworked by katabatic winds to form dune fields and widespread loess deposits supporting tundra ecosystems (David 1981;Begét 2001;Porter 2001;Wolfe et al 2004;Dyke 2005).…”