|
Ground cover of Mine Area No. 1 (Tables 1, 4, and 5, and Chart 1) in 2010 consisted of 35.7% live
<br />vegetation, 0.4% rock, 13.5% litter, and bare ground exposure of 50.4 %. In 2011, ground cover was
<br />measured at 41.5% live vegetation, 1.5% rock, 16.8% litter, and 40.3% bare ground exposure.
<br />Perennial cover across the unit averaged 30.7% in 2010 and 36.5% in 2011, with annual and biennial
<br />cover averaging 4.5% and 4.9 %, respectively. Dominant taxa detected in 2010 were needle- and - thread
<br />(Stipa comata), Indian ricegrass (Oryzopsis hymenoides), scarlet globemallow (Sphaera/cea coccinea),
<br />and blue grama (Bouteloua graci /is) with 8.5 %, 5.1 %, 5.0 %, and 4.0% average cover, respectively. In
<br />2011, dominant taxa were sand dropseed (Sporobo /us cryptandrus), blue grama, Indian ricegrass, and
<br />needle- and - thread with 9.4 %, 9.0 %, 4.0 %, and 3.7% average cover, respectively. With regard to
<br />diversity (Table 2 and Chart 3), Mine Area No. 1 revegetation exhibited two warm- season grasses, three
<br />cool- season perennial grasses and one perennial forb with between 3% and 40% relative cover in 2010.
<br />This area exhibited two warm- season grasses, two cool- season perennial grasses and one perennial forb
<br />with between 3% and 40% relative cover in 2011. Total relative cover for all forbs excluding noxious
<br />weeds in the Phase III area was 19.8% in 2010 and 15.0% in 2011. Plates 1 through 4 in Appendix A
<br />display typical revegetation in Mine Area No. 1 in 2010 and 2011.
<br />Ground cover of Mine Area No. 3 (Tables 1, 6, and 7, and Chart 1) in 2010 consisted of 32.4% live
<br />vegetation, 1.4% rock, 16.2% litter, and bare ground exposure of 50.0 %. In 2011, ground cover was
<br />measured at 35.7% live vegetation, 3.9% rock, 22.4% litter, and 38.0% bare ground exposure.
<br />Perennial cover across the unit averaged 22.6% in 2010 and 26.6% in 2011, with annual and biennial
<br />cover averaging 9.8% and 9.2 %, respectively. Dominant taxa detected in 2010 were Russian thistle
<br />(Sa /so /a tragus), blue grama, Indian ricegrass, and needle -and- thread with 8.2 %, 5.1 %, 4.1 %, and 3.7%
<br />average cover, respectively. In 2011, the dominant taxa were blue grama, Russian thistle, needle -and-
<br />thread, and Indian ricegrass with 12.1 %, 7.0 %, 3.0 %, and 3.0% average cover, respectively. With
<br />regard to diversity (Table 2 and Chart 3), Mine Area No. 3 revegetation exhibited two warm- season
<br />grasses, three cool- season perennial grasses and one perennial forb with between 3% and 40% relative
<br />cover in both 2010 and 2011. Total relative cover for all forbs excluding noxious weeds in the Phase III
<br />area was 37.8% in 2010 and 26.2% in 2011. Plates 5 through 8 in Appendix A display typical
<br />revegetation in Mine Area No. 3 in 2010 and 2011.
<br />Of note during collection and evaluation of these data is the fact that warm- season species typically
<br />exhibited substantially greater ground cover values in 2011 versus 2010. The causal agent for this
<br />observation is simply related to the amount and timing of precipitation received between the two years.
<br />In 2010, precipitation was approximately normal and early spring rains favored cool- season species. In
<br />2011, precipitation was somewhat elevated and rains were heavier during the early summer months,
<br />thereby favoring warm- season species. These precipitation patterns also had notable effects on area forb
<br />CEDAR CREEK ASSOCIATES, Inc.
<br />Page 14 Hamilton Mine - 2011
<br />Phase III Bond Release Evaluation
<br />
|