# Informations et ressources scientifiques sur le développement des zones arides et semi-arides

Accueil du site Doctorat États-Unis 1987 INFLUENCE OF LIVESTOCK GRAZING AND PROTECTION FROM LIVESTOCK GRAZING ON VEGETATIONAL CHARACTERISTICS OF BOUTELOUA ERIOPODA RANGELANDS (NEW MEXICO)

## ATWOOD, TERENCE LAYTON

Titre : INFLUENCE OF LIVESTOCK GRAZING AND PROTECTION FROM LIVESTOCK GRAZING ON VEGETATIONAL CHARACTERISTICS OF BOUTELOUA ERIOPODA RANGELANDS (NEW MEXICO)

Auteur : ATWOOD, TERENCE LAYTON

Université de soutenance : New Mexico State University

Grade : Doctor of Philosophy (PhD) 1987

Résumé
This study, conducted on Bouteloua eriopoda rangelands in southern New Mexico, was initiated in an attempt to quantify the effects of livestock grazing and protection from grazing on the vegetational characteristics of these ranges. Four study sites were examined, each of which had a livestock exclosure erected previous to the study. Ages of the exclosures in 1985 were 17, 22, 32, and 48 years. Vegetational attributes measured were density and frequency of perennial grasses and forbs, annual grasses and forbs, and density, frequency and canopy frequency of shrubs. At the site protected for 17 years, no differences (P $\leq$.05) were found in Bouteloua eriopoda density between the grazed and protected treatments. Bouteloua eriopoda density was greater (P $\leq$.05) on the grazed treatment than on the ungrazed treatment at the 22-year-old site, as was that of Sporobolus spp. Density of Bouteloua eriopoda was greater (P $\leq$.05) on the protected treatment at the site protected for 32 years, possibly due to favorable rainfall on the study site in preceding years. Density of Bouteloua eriopoda on the 48-year-old study site was greater on the protected than the grazed treatment at the time of, and for nine years following, the construction of the exclosure. In 1985, density of the species was greater (P $\leq$.05) on the grazed area. Density and frequency of perennial and annual forbs, and shrubs showed no relationship to either protection or grazing. It was concluded that livestock grazing is an important management tool in maintaining Bouteloua eriopoda rangelands, probably due to the species low tolerance to, and slow recovery from, drouth when ungrazed.

Mots clés : Range management, Biological sciences