|
annual and biennial (orbs was attributable to the weed hounds tongue ICvnoolossum
<br />• olficinalel.
<br />Total vegetation cover in the portion of the Sagebrush/Snowberry vegetation type to be
<br />affected by mining was 78.1 percent (Appendix 10D, Table tOD-11, while standing dead, litter,
<br />bare soil, and rock 0.5, 12.3, 9.1, and 0.0 percents, respectively. By comparison, in the
<br />extended reference area portion of the Sagebrush/Snowberry vegetation type, total vegetation
<br />cover was 72.7 percent (Appendix 10D, Table 10D-21, while standing dead, litter, bare soil,
<br />and rock 0.9, 18.7, 7.6, and 0.1 percents, respectively.
<br />Herbaceous biomass production averaged 830 pounds oven-dry per acre in the affected area
<br />(Appendix 100, Table 10D-31 and 1,345 pounds oven-dry per acre in the extended reference
<br />area (Appendix tOD, Table 10D-41. Higher values in the reference area relate to the locations
<br />of more of this type occurring in toe-slope positions in which supplemental moisture augments
<br />growth and a greater chance of a sample plot location with very high production conditions. In
<br />particular, four plots in the extended reference fell on such areas dominated by bracken fern
<br />lPteridium eguilinuml.
<br />Shrub density in the Sagebrush/Snowberry vegetation type affected area averaged 9,640 stems
<br />per acre, two-thirds of which was mountain Snowberry (Appendix tOD, Table 10D•51. the
<br />• remainder was mostly big sagebrush, with silver sagebrush and black chokecherry as the most
<br />important minor Species. In the extended reference area portion of this vegetation type, stem
<br />density averaged 9,324 stems per acre, again approximately two-thirds of which was mountain
<br />Snowberry (Appendix tOD, Table tOD-61. Big sagebrush again was most of the remainder.
<br />Black chokecherry and Douglas rabbitbrush were the most important minor species.
<br />Western Wheatgrass/Alkali Sagebrush Vegetation Type (Photos 33 through 40)
<br />Native perennial coot season grasses dominated the western wheatgrass/alkali sagebrush
<br />vegetation type with 45.8 percent of total vegetation cover (Appendix 10E, Table t0E-11. By
<br />far, the bulk of this cover is provided by western wheatgrass, but Letterman needlegrass
<br />/Achnatherum /ettermaniiJ, oniongrass (Me/ica bu/basal, slender wheatgrass, and Agassiz
<br />bluegrass are all locally abundant in the type. Mountain brome and Junegrass also occur with
<br />rather high frequency, though they provide little cover. Early in the year, and in wet years, as
<br />was the case in 1997, native perennial fortis provide substantial cover. The 1997 data indicate
<br />they were the second most abundant lifeform with 26.1 percent of total vegetation cover.
<br />Mules ears /Wyethia amp/exicau/is/, arrowleaf balsamroot, and timber milkvetch were often
<br />extensive components of the ground cover. Western yarrow, bracted aster (Aster foliaceous),
<br />showy goldeneye, longleaf phlox, and Pacific aster /Virqu/aster ascendensl were important
<br />• contributors to cover also. Tapertip onion, fringed thistle /Cirsium cenfaurael, Nuttall larkspur
<br />/De/phinium nuts//ienuml, and lambstongue groundsel were also commonly encountered, but
<br />57 Revised 9198
<br />....... c--,,,.,.;m:ice:°?-5.?i::3Zti: ~$.'iu~R.SG:rv.~b':.. ..x~ :S~9i1.fib?Snf:~i3'°'ia~...~..e:' `st'i.T.. ~ ::=rt;-. a
<br />
|