Quaking Aspen Ecology on Forest Service Lands North of Yellowstone National Park

• Published in: Natural resources and environmental issues 2011-01, Vol.16, p.1
• Main Authors: Kimble, David S, Tyers, Daniel B, Sowell, Bok F
• Format: Article
• Language: English
• Subjects: Animal behavior; Cattle; Elk; National parks
• ISSN: 1069-5370; 2379-2299

Quaking aspen (Populus tremuloides) occupy a small area in the northern Rocky Mountains, but are highly vabJed as wildlife habitat. Aspen stands in and around Yellowstone National Park commonly consist of jew, large, mature overstory stems and numerous root suckers that do not grow above the browsing reach (;::: 2 m) of most wild ungulates. Our primary objective was to determine if the recrnitment or density of aspen stems> 2 m tall had changed from 1991 to 2006 on a portion of the Gallatin National Forest. The same aspen stands were surveyed in 1991 and 2006 in the 560 lan2 study area (n = 316). Secondary objectives were to detennine if aspen density was influenced by elk (Cervus elaphus) browsing, conifer establishment, and cattle (Bos spp.) grazing. Mean recrnitment stem density did not change from 1991 to 2006 (P = 0.95). Density of stems> 2 m declined 12 percent from 1991 to 2006 (P = 0.04), which indicates that recrnitment stems are not being produced at a sufficient rate to replace aging overstories. Areas with the greatest elk densities had the lowest recruitment stem densities and contributed the most to the decline. Although elk browsing seemed to play the largest role, conifer establishment and cattle grazing have also negatively impacted overstory recrnitment in aspen stands. Even though elk numbers on the Northern Yellowstone Winter Range have declined since wolf reintroduction, aspen recrnitment has not increased at the landscape level on the Gallatin National Forest. [PUBLICATION ABSTRACT]