In 1978, a ten year project was begun to examine
the synecological effects of livestock grazing riparian
ecosystems. A multitude of biotic arid physical factors,
many which were unique to riparian ecosystems, interacted
to form a complex and diverse riparian ecosystem.
A total of 256 stands of vegetation representing 60
discrete plant communities were identified. Twenty
species of mammals and 81 species of birds were sited
utilizing the area from May-October.
Approximately one-half of the riparian vegetation
bordering Catherine Creek was excluded from livestock
grazing. Ten plant communities were intensively sampled
in grazed and exclosed areas during three growing
seasons to determine some of the impacts a late season
grazing scheme has on riparian vegetation. Three plant
communities displayed significant species composition
and productivity differences. These commmunities were
within' the meadow and Doug1az Hawthorne (Crataegus douglasii) vegetation types and were utilized more heavily
by livestock than any other communities sampled. In
addition succession appeared to be retarded by grazing
on gravel bars dominated by black cottonwood (Populus
trichocarpa) saplings and willows (Salix spp.). Few differences
were recorded in other plant communities sampled.
Late season grazing had few short term impacts on
avian populations censused from May-October. There was
a significant decrease in small mammal populations after
grazing in all communities sampled. However, by the
following August small mammals had recolonized the
grazed plant communities in essentially the same species
composition and densities.
Grazed areas had significantly greater streambank
losses than areas that were not grazed. While overwinter
losses accounted for much of the streambank erosion, the
erosion and disturbance caused by livestock grazing and
trampling was enough to create significantly greater
streambank losses in grazed areas compared to ungrazed
areas.
Positive characteristics of a late season grazing
scheme on. the riparian zone included increased late
season livestock production, good plant vigor and productivity,
minimal soil disturbance, and minimal short
term disturbance to wildlife populations dependent on
riparian ecosystems