PERMFILE134458

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: Exhibit 32A Baseline Vegetation Study 1996, Sylvester Gulch Facilties Area
• Media Type: D
• Archive: No

•
IV. OAKBRUSH COIVIl~IUNITY
OAKBRUSH CONII~IUMTY: GENERAL DESCRIPTION
The oakbrush vegetation community is the dominant vegetation community within the
study azea. It is present on the steep east and west-facing slopes above the drainage
bottom of Sylvester Gulch. The oakbrush community also intermixes with the other
vegetation communities within the study azea, particularly as physical characteristics
and topography approach the optimal niche limits for other plant species. This
community is composed of three vegetative layers; the tall shrub and tree stratum (>3
meters in height), a medium stratum composed of shrubs and sapling trees (1-2 meters
in height), and a low herbaceous graminoid and fort component (< 0.5 meters).
Figure 2 provides an illustration of the interior of the oakbrush community. Based on
both vegetation cover and woody plant density parameters, Quercus gambelii
(Gambel's oak) is the dominant plant species in this community, and comprises the
majority of the canopy of the community. The medium stratum is dominated by three
woody species; Amelanchier alnifolia (serviceberry), Prunus virginiana (chokecherry),
and Symphoricarpos rotundifolius (snowberry). The most common component of the
herbaceous layer is Poa pratensu (Kentucky bluegrass). Within the community, woody
shrub and tree species significantly dominate, with woody plant species comprising
• 71.87 percent of the total vegetation cover and 88 percent of the relative vegetation
cover. Competition for sunlight, nutrients, and moisture regulate the composition of
this community. Underneath the upper two vegetative layers, little sunlight reaches the
ground. Sunspots, ephemeral sunlight penetration areas, aze the locations of the most
dense growth of herbaceous grasses and forts. In several areas, small openings
(< 1000 square feet) in the oakbrush canopy have allowed graminoids and low shrubs
to become established and outcompete the oakbrush. Relict individuals of Pseudotsuga
mensieai (Douglas fir) and luniperus osteosperma (Utah juniper) may also be
encountered within the oakbrush community. These individuals pre-0ate the
development of the oakbtvsh community or grew and flourished in openings in the
canopy, as both are shade intolerant species.
QUANTITATIVE SAMPLING RESULTS
The general composition of the oakbrush community was that of a multiple storied low
forest. The stories were composed of a tree or tall shrub component (> 3 meters in
height), a medium height (1-2 meter) shrub component, and a low herbaceous
graminoid and fort component. The upper canopy was dominated by Quercus
gambelii with occasional Arnelanchier alnifolia, and Prunus virginiana individuals
present in the canopy. The medium height shrub understory was dominated by
Amelanchier alnilolia, Prunus virgmiana, and Symphoricarpos rotundifolius.
• Occasional Rasa uvodsii (Wood's rose), and Swida sericea (red osier dogwood)
individuals were encountered in this layer. ilfahonia repens (Oregon grape), and Poa
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