2008-03-13_REPORT - C1981019 (2)

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2.2.4 EP041 EP041 is comprised of 30.8 acres of moderately sloping revegetation. This unit was seeded in 2003 and therefore, has undergone four growing seasons prior to sampling in 2007. A total of 33 plant taxa were observed in the unit (see Table AB-1). Ground cover in EP041 consisted of 72.7% live vegetation, 0.1% rock, 19.3% litter, and bare soil exposure of 7.9%. Perennial cover across the unit averaged 44.7% with annual and biennial cover averaging a significant 27.9%. The dominant taxa were cheatgrass, thickspike wheaigrass, streambank wheatgrass, and slender wheatgrass, with 22.3%, 11.5%, 10.9%, and 7.6% average cover, respectively. Woody plant density was determined from 15 belt transects. Density (Table 2) totaled 2.7 young and mature stems per acre with antelope bitterbrush (Purshia tridentata) the dominant woody plant. With regard to diversity, EP041 exhibited 5 perennial grass and 0 perennial fortis with between 3% and 50% relative cover. r ® , ® s t ~ \ cne.ry.,..OOm~1unt ~ ~ -" ~ ~ / ~ ~ '~ ,, i I ~ O ~ _ ~.~.a. T~MN ® ®~ ~ A 0 O A '~1 r -- / Noxious weeds appear to be controlled in this unit, however populations of Canada thistle were observed. Annual bromes are present with 26.5% cover and should be monitored in the coming years. If monitoring reveals expansion, use of the herbicide Plateau is recommended in conjunction with spot reseeding. Overall, Unit EP041 should be monitored closely to evaluate if intervention is needed to Facilitate progress toward bond release. Rio Tinto Energy America/Colowyo Mine Page 20 Revegetation Monitoring - 2007 • • • • • • • • • • • • • • • • • • • r • • • • • • • • • • • • • • • • r