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Ecosystems
within the
Portneuf River Basin
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The
Portneuf River is located at the
northern edge of the
Great Basin ecosystem, which covers all of Nevada and parts of Utah,
Idaho, and California. At lower elevations the Great Basin is desert,
cooler on average than the more southern deserts in North America, but
dry and
hot in the summer months. Large expanses of the Great Basin desert were
historically dominated by sagebrush, and sagebrush steppe was a
dominant vegetation
type on lower elevations of the Portneuf River Ecosystem. Much
of the flatter land in this area that once supported sagebrush steppe
communities has been converted to
agricultural land uses. The southern end of Pocatello, towards the
Portneuf gap, has irrigated crop land, and much of the Marsh Creek
valley is used for
crops and for grazing livestock. This large concentration of
agricultural land use is evident on the map to the right.
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The
distribution of plant associations
within the Portneuf Basin
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The Portneuf
watershed still contains areas that are representative of the
sagebrush steppe ecosystem that was widespread a century ago. Land on
either side of I-15 between Inkom and McCammon has been grazed by
livestock,
but, apart from areas that have burned in the last 10 years, sagebrush
is still the dominant plant species. Idaho State University owns a
65-acre site on
the east bench of Pocatello, the Barton Road Ecological Research Area,
which is used
for research and teaching. This site has some very healthy stands of
sagebrush, and has been protected from livestock long enough to have
well developed
microbiotic crusts.
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Mink
Creek
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Meadow
at Scout Mountain
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Big Sagebrush
(Artemisia tridentata)
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Aspen
and Douglas Fir near Cherry Springs
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The
land
within
the Portneuf
watershed rises
from an
elevation of 1327 m (4359 feet) where
the river enters American Falls Reservoir to over 2749 m (9000 feet) at
the top
of Haystack Mountain. At higher elevations average temperature drops
and
precipitation typically increases. Both factors contribute to changes
in plant
communities along elevational gradients. The lower mountain slopes can
support
dense stands of junipers in areas that have not burned for 50 years,
and plant
communities dominated by perennial grasses and forbs where there is not
a
closed canopy of junipers.
At somewhat higher elevations, and on lower
slopes
that are slightly wetter, aspens and maples provide our fall color.
Moving
further up the mountains, dense stands of conifers, including Douglas
fir, are
mixed with stands of aspen and maple. None of the peaks within the
Portneuf
watershed are high enough to exceed treeline, but there are many open
meadows
that provide gorgeous displays of wildflowers during the summer and
fall. Along the Portneuf River, and along streams that
feed it, water supports distinct riparian plant communities. Although
most of
the river channel within the center of Pocatello has been channelized,
there
are areas upstream and downstream of the channel that illustrate what
this
river channel looked like a century ago. Cherry Springs, located in the
Caribou
National Forest southwest of Pocatello, is an excellent example of a
riparian
area that has been protected from development and livestock. |
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