Effects of Grazing on the Vegetation of the Blackbrush Association

Abstract

Four communities or sites dominated by blackbrush (Coleogyne ramosissima Torr.) were studied in the Kaiparowits Basin of southern Utah and northern Arizona. One site has been heavily grazed yearlong for about 100 years; the second has been lightly to moderately grazed in winter for 3 years; the third has had 10 years of recovery from heavy grazing; and the fourth is a relic, ungrazed blackbrush ecosystem. Soils were 87 to 99% sand and gravel with mean pH's 8.2 to 8.5. The relic site had significantly more herbaceous vegetation cover (composed primarily of perennial grasses) and total cover than all other sites. The relic site also had significantly more shrub and cryptogamic cover than the heavily grazed and recovery sites. The recovering site showed no significant differences than the heavily grazed site for any of the measured parameters.