Yellowstone's Northern Range - Greater Yellowstone Science ...

Figure 4.2. Willow
distribution in
Yellowstone National
Park. The largest
concentrations of
willow are south of
Yellowstone Lake
along the upper
Yellowstone Rivel; in
the southwest comer
of the park, and in
tributaries of the
Madison River near
the west boundmy.
Map by the
Yellowstone Spatial
Analysis Center and
the Yellowstone
Center for
Resources.
has led to predictions of decreases in coyote
numbers (R. Crabtree, Yellowstone Ecosystem
Stud., pers. commun.), which may permit an
increase in pronghorn (Berger 1991), the ungulate
species most dependent upon sagebrush, and
currently regarded as a species of special concern
on the northern range (see pronghorn research
recommendations, Chapter Seven). Further
research into the ecology of the various sagebrush
species across the northern winter range is needed,
especially into the factors contributing to the
decline of the Wyoming SUbspecies, and the
apparent thriving of the basin subspecies. The role
of pronghorn in the vitality of sagebrush and
climate change appears crucial. Continued
monitoring of all of these interactive forces in the
BLA seems warranted.
WILLOWS
About one-half of one percent (0.54 percent)
of the Yellowstone Park's willow
communities are on the northern
range (Figure 4.2). The greatest
concentrations of willows in
Yellowstone National Park are
south of Yellowstone Lake, the
southwest corner of the park in
the Bechler River area, and near
the west boundary north of the
Madison River. Willow abundance
in the park is almost
entirely defined by elevation and
precipitation; areas that are
above 7,000 feet and have more
than 20 inches of annual precipitation
comprise 74 percent of the
park's willow communities, and
areas that are above 7,000 feet
andlor have more than 20 inches
of annual precipitation comprise
more than 99 percent of the
park's willow communities.
These are high-elevation sites,
not on the winter ranges of
ungulates, except possibly that of
moose.
THE NORTHERN RANGE
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Willows have been described as an "insignificant
component" of the Yellowstone area for at
least the past 20,000 years (Mullenders and
Coremans 1996, Mullenders et aJ. 1996). That
should be taken to mean that they occupy comparatively
little area. It should not be taken to mean
that they do not have significant ecological effects
on northern range plant and animal communities, a
subject dealt with later in this section.
Declines in willows were noted early in the
northern range's written history. Houston, based
on comparison of historic photographs with
modern retakes, estimated that during the past
century, willows may have declined in area from
about 0.8 percent of the northern range (that is,
slightly less than 1 percent) to about 0.4 percent
(that is, less than half of I percent). Houston
(1982) and Chadde and Kay (1991) published
photographic evidence of heavier willow growth
along some park streams prior to 1900.
There are approximately 24 species of
c=J Northern Winter Range
_
Willow Habitat
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