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populations. Most forb taxa in the area are cool- season species and therefore, cover values dropped in
<br />2011, as did cool- season grasses, in comparison to warm- season species.
<br />3.3 Ground Cover Findings - Reference Areas
<br />Ground cover of Sagebrush Reference Area A (Tables 1, 8, and 9, and Chart 1) in 2010 consisted of
<br />22.7% live vegetation, 0.5% rock, 23.1% litter, and bare ground exposure of 53.6 %. In 2011, ground
<br />cover was measured at 20.7% live vegetation, 0.7% rock, 19.4% litter, and 59.2% bare ground
<br />exposure. Perennial cover across the unit averaged 22.5% in 2010 and 20.7% in 2011, with annual and
<br />biennial cover averaging 0.2% and 0.0 %, respectively. Dominant taxa detected in 2010 were big
<br />sagebrush (Artemisia tridentate var. wyomingensis), bottlebrush squirreltail (Sitanion hystrix), and
<br />galleta (Hi /aria jamesii) with 12.4 %, 3.3 %, and 3.0% average cover, respectively. In 2011, the dominant
<br />taxa were big sagebrush, blue grama, and broom snakeweed (Gutierrezia sarothrae) with 12.9 %, 1.7 %,
<br />and 1.5% average cover, respectively. With regard to diversity (Table 2), Sagebrush Reference Area A
<br />exhibited one warm- season grass, two cool - season perennial grasses and no perennial forbs with
<br />between 3% and 40% relative cover in both 2010 and 2011. In this regard, this native reference area
<br />would have failed the diversity standard in both years. Total relative cover for all forbs excluding noxious
<br />weeds in the reference area was 2.1% in 2010 and 4.5% in 2011. Plates 9 through 12 in Appendix A
<br />display typical vegetation conditions in Sagebrush Reference Area A in 2010 and 2011.
<br />Ground cover of Sagebrush Reference Area B (Tables 1, 10, and 11, and Chart 1) in 2010 consisted
<br />of 19.9% live vegetation, 0.5% rock, 29.1% litter, and bare ground exposure of 50.4 %. In 2011, ground
<br />cover was measured at 20.6% live vegetation, 1.1% rock, 30.8% litter, and 47.5% bare ground
<br />exposure. Perennial cover across the unit averaged 19.2% in 2010 and 20.3% in 2011, with annual and
<br />biennial cover averaging 0.7% and 0.3 %, respectively. Dominant taxa detected in 2010 were big
<br />sagebrush, bottlebrush squirreltail, and western wheatgrass (Agropyron smithiI with 9.5 %, 4.3 %, and
<br />2.7% average cover, respectively. In 2011, the dominant taxa were again big sagebrush, bottlebrush
<br />squirreltail, and western wheatgrass with 9.2 %, 3.0 %, and 2.5% average cover, respectively. With
<br />regard to diversity (Table 2), Sagebrush Reference Area B exhibited one warm - season grass, two cool -
<br />season perennial grasses and no perennial forbs with between 3% and 40% relative cover in 2010. This
<br />area exhibited two warm- season grasses, three cool - season perennial grasses and no perennial forbs
<br />with between 3% and 40% relative cover in 2011. In this regard, this native reference area would also
<br />have failed the diversity standard in both years. Total relative cover for all forbs excluding noxious weeds
<br />* During data collection, Cedar Creek biologists noted that the sagebrush overstory within these reference areas (as
<br />well as all surrounding areas) exhibited elevated levels of decadent and dead plants. It appeared that the stand of
<br />sagebrush was recovering, especially in 2011, but standing dead was still elevated over normal conditions.
<br />CEDAR CREEK ASSOCIATES, Inc.
<br />Page 15 Hamilton Mine - 2011
<br />Phase III Bond Release Evaluation
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