Guenther, Debra, Thomas Stohlgren, and Paul Envangelista. 2004. A comparison of a near-relict site and a grazed site in a pinyon-juniper community in the Grand Staircase-Escalante National Monument, Utah. In Charles van Riper III and Kenneth Cole. The Colorado Plateau: Cultural, Biological, and Physical Research. Tucson: The University of Arizona Press
RELEVANT TO: LIVESTOCK GRAZING
GRASSLANDS/SHRUBLANDS
MONITORING/ADAPTIVE MANAGEMENT
DESCRIPTION OF DOCUMENT
This is a field comparison of vegetation on two isolated mesa tops in the Colorado Plateau: No Man's Mesa, grazed for two years 73 years earlier; and Deer Spring Point summer grazed by livestock since the late 1800s. Six multi-scale modified-Whittaker plots (a nested design useful for capturing species diversity and comparison at 1,10, 100, and 1,000 square meter scales) were placed in each of the two mesa tops.
The following vegetation features were compared: cover of bare ground, duff, woody debris, foliar canopy cover and average height of vegetation by plant species, and biological soil crust development. Soils were closely identical; deer and elk are not present.
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MAJOR FINDINGS
- Young cryptobiotic crust cover 27% less and older cryptobiotic crust cover 60% less on Deer Spring Point.
- Few annual species on either mesa, but significantly more on Deer Spring Point, "...with the potential for future large-scale invasion."
- Significantly more subshrub cover on No Man's Mesa; significantly more shrub cover on Deer Spring Point, resulting in greater total vegetation cover. "The increase in shrub and litter cover increases fuel for possible future fires. Data gathered near the Buckskin Mountain area of the monument indicate that fire disturbance greatly increases cheatgrass and other exotic species cover if a seed source is present...cheatgrass is present on Deer Spring Point...Once a cheatgrass fire cycle is introduced into this system, a negative feedback loop is formed wherein the cheatgrass provides fuel for future fires which in turn allows it to persist and spread further [citation]" (p. 161).
- Although less shrub cover on No Man's Mesa, considerably more diversity, including six species of shrubs not present on Deer Spring Point. Eighty-six percent of shrub cover on Deer Spring Point was provided by only three shrub species.
- No exotic species in the plots on No Man's Mesa; four exotic species on Deer Spring Point plots.
- Cumulative native species richness on No Man's Mesa: 84 species; Deer Spring Point: 71 species.
- Remarkably high native species diversity on both mesas; "Perhaps the geology type or relative isolation can explain this phenomenon" (p. 161).
- At a 1 sq meter scale, there is greater species richness on Deer Spring Point; but homogenization of species richness at the 6,000 sq meter and 1 hectare scale "...which is the scale with which managers are most concerned."
QUESTIONS THIS RAISES FOR THE THREE FORESTS
- Which sites, currently unprotected from disturbance on each Forest offer the most potential to regain native biodiversity with rest from historical and current disturbance?
- What documentation of biological soil crust habitat/presence exists on each of these Forests?
FOREST MANAGEMENT SIGNIFICANCE
- Loss of species biodiversity can take place gradually over long periods of time: Species diversity is 16% less on Deer Spring Point. This shows the importance of large blocks of roadless and livestock-free areas within the Forests.
- Isolation can provide a buffer for native species diversity and richness; this shows the importance of roadless areas.
- Homogenization of biodiversity at a large scale means a loss of richness in our national public lands: Large blocks of roadless and livestock-free areas are essential, given the inability of short-term monitoring to detect such changes, but the scientific evidence that livestock grazing, roads and ORVs lead to such homogenization.
- ORVs should be allowed only on designated roads and routes.