Escarpments and the Foothill Transition - Mountains and Plains: The Ecology of Wyoming Landscapes - page 169

reduces the number of sprouts. When aspen groves are
fenced to exclude large herbivores, the small sprouts
often grow into trees (fig. 10.15).
An interesting perspective on decadent aspen stands
was presented by U.S. Forest Service ecologist norbert
DeByl e. 46 H e suggested that one of the causes is political
pressure to maintain elk populations at the same high
level year after year, to satisfy hunters, guides, and game
and fish agencies that depend on license sales. DeByle
reasoned that in the 1800s the number of elk fluctu-
ated considerably, largely stemming from higher mor-
tality during some winters than others, and that aspen
sprouts had a better chance of developing into trees
during periods when the browsing pressure was low
Fig. 10.14. (right) An aspen grove in the Greater Yellowstone
Area that appears to be dying, most likely because of excessive
browsing by elk (see chapter 15). Mountain big sagebrush,
arrowleaf balsamroot, and other foothill plants occur in the
area; lodgepole pine and limber pine can be seen in the back-
ground. elevation 7,100 feet.
Fig. 10.15. (below) Aspen groves usually recover quickly when
protected by a fence from browsing, such as in this area in
northwestern Wyoming. Aspen exists outside the fenced
exclosure, to the right, but only as small, heavily browsed root
sprouts. See chapter 15.