Geoscience Reference
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Bar deposit
Suspended sediment
Sandbar meadow
Without
willow or
cottonwood
Cottonwood woodlands
Fire
or
beaver
Fire
or
beaver
Young (1-29 yrs)
Annual
flooding
Basin big
sagebrush
Saltcedar
willow
Meadow
Middle-aged (30-79 yrs)
Old (>80 yrs)
?
Periodic
flooding
or fire
Skunkbush sumac
Rabbitbrush
Snowberry
Rose shrubland
Saltcedar
Skunkbush sumac
Rabbitbrush
shrubland
Periodic
flooding
or fire
Prolonged inundation
?
?
Greasewood
shrubland
Fig. 4.11. Probable riparian succession on new point bars
along the meandering channel of the Bighorn River east of
Lovell. As indicated, succession has changed considerably
in this area since the introduction of saltcedar (also known
as tamarisk). With flood control, many point bars are not
suitable for the establishment of cottonwood seedlings. there-
fore, the proportion of the landscape dominated by cotton-
wood decreases as older trees die; shrublands have become
more common. elevation 3,700 feet. Adapted from Akashi
(1988).
wood seedlings are observed more frequently along the
Shoshone, perhaps because favorable flooding is more
frequent there. By whatever means, habitat for seedling
establishment is created more often. Similarly, young
narrowleaf cottonwoods are common along the free-
flowing Gros Ventre River in Jackson Hole.
16
the riparian landscapes along meandering and
braided streams change so rapidly that it is difficult to
think about succession in the traditional sense. Before
the biota has a chance to form a relatively stable com-
munity, the river channel typically shifts to a new loca-
tion or a fire occurs (because of the abundant fuel).
Still, several successional trends have been observed.
commonly, cottonwoods and some willows are the pio-
neer species, with gravel bars colonized by narrowleaf
cottonwood in western Wyoming and eastern idaho,
sandbars by sandbar willow, and mudflats by Booth's
but as they age and the channel moves farther away,
the trees die and give way to shrubland or grassland.
As noted, tree mortality in such places could be caused
by a dropping water table as the channel moves across
the floodplain, which enables the invasion of plants
that are more tolerant of water stress and also possibly
benefit from more oxygen in the soil, such as red osier
dogwood, Rocky Mountain juniper, silver buffaloberry,
skunkbush sumac, and rubber rabbitbrush. the sup-
pression of disturbances along some rivers allows the
development of self-perpetuating shrublands, and also
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