PERMFILE47344

• Permit No: C1994082
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Doc Name: 1990/1992 Vegetation Baseline Report
• Section_Exhibit Name: Tab 10 Attachment 10-1
• Media Type: D
• Archive: No

• Tiedeman and Terwilliger 1978). Within the type there was a gradient of moisture and soil
depth. On the driest sites, with the shallowest soils, serviceberry was dominant along with
chokecherry, while Gambel's oak was nearly or entirely absent. Mountain Brush stands in
the Yoast study area of this sort correspond most closely to the Mixed Mountain Shrub /
Dark Brown Loams unit of the classification of Piceance Basin vegetation by Tiedeman and
Terwilliger (1978), in which serviceberry and snowberry are the dominants. On the most
moist Mountain Brush sites of the Yoast study area, where soils are deeper, Gambel's oak
dominates, with varying lesser amounts of serviceberry and snowberry. Such areas
correspond to Tiedeman and Terwilleger's Mixed Mountain Shrub / Pachic Dark Brown
Loams. A drier phase of Mountain Brush occurring on moderately deep to deep soils,
dominated by serviceberry, was clearly transitional to sagebrush, based on the droughtiness
of the sites and the composition of the understories in which the moist (orbs of the Gambel's
oak stands (e.g. Aster engelmannii, Galium boreale, Osmorhiza spp., Vicia americanal are
absent or much reduced in both the serviceberry-dominated stands of Mountain Brush and
Sagebrush.
The Steep Mountain Brush vegetation type, occurring on shallow and droughty soils of very
• steep slopes often on south and west exposures, corresponds perhaps as closely to dryland
types such as the High Elevation Pinyon-Juniper/ Shallow Sandy Loam of Tiedeman and
Terwilliger (1978) as to other Mountain Brush types, except in the absence of pinyon pine
and juniper trees. The presence of a mix of drought-tolerant shrub species such as
mountain mahogany, bitterbrush, serviceberry, and Douglas rabbitbrush along with
drought-tolerant herbaceous species such as bluebunch wheatgrass, sun sedge, few-flower
goldenrod, and arrowleaf balsamroot indicates that the sites on which Steep Mountain Brush
is found are distinctly dryer than the relatively moist sites typical of Mountain Brush
itself.
Mountain Brush vegetation corresponds to the Brushy Loam range site (No. 238) identified
by the SCS. As with most range sites, Brushy Loam is broadly defined since it applies to a
large area, including nearly the entire western third of Colorado.
The Sagebrush vegetation type of the Yoast study area corresponds to the High Elevation Big
Sagebrush /Dark Brown Loams unit of Tiedeman and Terwilliger (1978). The abundance of
big sagebrush, Douglas rabbitbrush, and snowberry, and the small, but frequent presence of
• serviceberry characterize both units. However, whereas in the Tiedeman and Terwilliger
unit, Astragalus preussii was a dominant fort, it does not occur in the Yoast baseline or
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