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Accueil du site → Master → Etats Unis → 1982 → Synecological effects of cattle grazing riparian ecosystems

Oregon State University (1982)

Synecological effects of cattle grazing riparian ecosystems

Kauffman, John Boone

Titre : Synecological effects of cattle grazing riparian ecosystems.

Auteur : Kauffman, John Boone

Université de soutenance : Oregon State University

Grade : Master of Science 1982

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


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