Historic aspen recruitment, elk, and wolves in northern Yellowstone National Park, USA

We conducted an analysis of aspen (Populus tremuloides) overstory recruitment on the northern range of Yellowstone National Park (YNP) using information provided in a monograph published by Warren (Warren, E.R., 1926. A study of beaver in the Yaney region of Yellowstone National Park, Roosevelt-Wildl. Ann. 1, 1–191), increment cores collected from riparian aspen stands in 1998, and an extensive random sample of aspen increment cores collected over YNP’s entire northern range in 1997 and 1998. We summarized aspen size classes reported by Warren and estimated overstory origination dates of the stands he described using a linear regression based on our riparian aspen diameter/age relationship. Applying our regression results to Warren’s diameter measurements, we predicted that the stands measured by Warren contained aspen that originated between approximately 1751 and 1920. The random set of aspen increment cores were used to analyze the age distribution of the current aspen overstory on YNP’s northern range. These increment core data showed that approximately 10 % of the current overstory aspen originated before 1871