Postglacial vegetation history of southeastern Wyoming, U.S.A.

Abstract

Paleoenvironmental records from southeastern Wyoming have been compiled to show the development of forests in the Medicine Bow Mountains. The late-glacial period had little to no tree cover and a landscape dominated by alpine tundra, or alpine steppe-like conditions based on high abundances of Artemisia pollen. Initial conifer forest development began after 13,000 calibrated years Before Present (cal yr BP) with patchy, mixed fir-spruce-pine forests forming throughout the Medicine Bow Mountains. At lower tree line, pines in these forests contained limber pine based on pollen and macrofossil data, whereas at mid-and high elevations pine trees were most likely lodgepole pine. Forest densities increased after 9000 cal yr BP, with upper elevations dominated by Engelmann spruce and subalpine fir, while lower elevations were dominated by lodgepole pine that replaced limber pine. Modern forest conditions began to form after 5000 cal yr BP. The timing of past vegetation change in southeastern Wyoming appears consistent with those observed in the Greater Yellowstone region though pollen assemblages vary regionally.

Medieval warming initiated exceptionally large wildfire outbreaks in the Rocky Mountains

“…Fossil pollen data indicate that the regional vegetation remained similar to the regional vegetation observed today throughout the past 2,000 y. Some records show an increase in spruce and fir abundance in the past 500-1,000 y (24)(25)(26)(27), and regional timberline changes may be consistent with an expansion of meadows and parklands at the highest elevations (28,29).…”

Systematics of the ectomycorrhizal genusLactariusin the Rocky Mountain alpine zone

“…Pollen data from Blacktail Pond, Yellowstone National Park, suggest that montane, mid-elevations in the northern greater Yellowstone ecosystem (Montana, Wyoming) were occupied by alpine tundra (Betula, Salix, many herbaceous taxa) similar to that of the present Rocky Mountain alpine vegetation during the last glacial period (14 000-11 500 calibrated years before present) (Krause and Whitlock 2013). Alpine vegetation also appears to have dominated areas in the southern Rocky Mountains (Wyoming, Colorado) 17 500-12 600 calibrated years before present (Minckley 2014). Both studies suggest the presence of broad, low-elevation glacial refugia for arcticalpine life in the Rocky Mountains along the glacial front and, along with this study, lend support to the idea that arctic-alpine Lactarius species (and many other ectomycorrhizal fungi) may have occupied tundra areas south of the icesheets during cooler weather during the last glacial maximum and then dispersed upward in elevation and northward as the glaciers and ectomycorrhizal host plants retreated.…”