Aspen age structure and stand conditions on elk winter range in the northern Yellowstone ecosystem
tremuloides) age structure and stand conditions on elk winter range in the northern
Yellowstone ecosystem. The elk winter ranges studied were the northern range in
Yellowstone National Park (YNP) and the Gallatin National Forest and the
Sunlight/Crandall elk winter range in the Shoshone National Forest.
I found significant differences when comparing aspen stands inside and
outside of YNP borders. The aspen stands in the Gallatin and Sunlight/Crandall areas
had a greater incidence of tall aspen suckers and stems in the 1-4, 5-9, and 10-19 cm
DBH classes. Aspen stems within YNP had a significantly higher percentage of stems
with high levels of bark damage (>66% of bark surface damaged on the lowest 3 m of
stem) than aspen stems in stands in the Gallatin or Sunlight/Crandall.
An aspen age structure was developed using 598 increment cores. The aspen
age structure in YNP was significantly different than the age structures of the Gallatin
and Sunlight/Crandall elk winter ranges. The Gallatin and Sunlight/Crandall areas did
not have significant differences in their age structures. The greatest differences
between YNP and the National Forest areas was in the younger age classes, measured
as aspen stems originating between 1920-1989.
Within YNP, I found that the aspen age structure, size class distribution,
incidence of tall suckers, and the percentage of browsed suckers of the scree habitat
type was significantly different than the xeric and mesic habitat types. Scree forms a
"natural exclosure" where ungulate browsing is reduced.
Aspen stands have successfully recruited new stems into their overstories in all
habitat types from 1880-1989 on the Sunlight/Crandall elk winter range and the
Gallatin's portion of the northern range. Within YNP, aspen stands successfully
recruited new overstory stems between 1860-1929 in all habitat types. Since 1930,
YNP aspen have successfully recruited overstory stems mostly in scree habitat type
stands and other areas of reduced browsing pressure. I discussed several potential
ecological factors impacting aspen overstory recruitment and conclude that changes in
ungulate browsing patterns best explains the spatial and temporal pattern I observed.
Advisor:Kimerling, A. Jon; Ripple, William J.
School:Oregon State University
School Location:USA - Oregon
Source Type:Master's Thesis
Keywords:populus tremuloides yellowstone national park elk food
Date of Publication:06/27/2001