2008-03-13_REPORT - C1981019 (2)

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2.3 West Pit 2.3.1 WP008 WP008 is comprised of 7.9 acres of steeply sloping revegetation that has a predominately northwesterly aspect. This unit was seeded in 2000 /~ .1 O and therefore, has undergone seven growing I( . seasons prior to sampling in 2007. A total of 29 plant taxa were observed in the unit (see Table AB- O O O O 1). Current annual production across the unit ~ ; ` averaged 1,337.5 pounds per acre in 2007 with ~ ~ ® ® O O O perennial grasses and annual grasses the dominant categories (see Figure 7). Ground cover in WP008 `~ consisted of 71.9% live vegetation, 0.8% rock, ~ ~ O 20.3% litter, and bare soil exposure of 7.1%. Perennial cover across the unit averaged 52.7% with j annual and biennial cover averaging 19.2%. The dominant taxa were thickspike wheatgrass, Siberian `'"'°'"""" wheatgrass, cheatgrass, Japanese brome, and ~ ~ \ smooth brome (Bromus inermis) with 16.2%, ~x ~ 10.8%, 10.1%, 9.1%, and 6.1% average cover, ` respectively. Woody plant density was determined ~~` from 20 belt transects. Density (Table 2) totaled 520.0 young and mature stems per acre with four- ~ - •~-•f,.,.. ~~ ~ ~. wing saltbush (Atriplex canescens} the dominant '"- woody plant. With regard to diversity, WP008 exhibited 5 perennial grasses and no perennial fortis with between 3% and 50% relative cover. Unit WP008 currently fails the bond release diversity standard of 3 perennial grasses and 1 perennial forb with between 3% and 50% relative cover. However, this unit passes bond release comparisons to the reference areas for both cover and production (see Charts 3 and 5). This unit does not presently meet the woody plant density standard of 90% of 1000 stems per acre and will probably not meet this in the foreseeable future due to the heavy competitive grass cover. See Appendix AA -Section 6.3 for a discussion on options and recommendations with regard to woody plant density. Noxious weeds appear to be well controlled in this unit, however there were observations of Canada thistle. Annual bromes currently represent 19.1% cover in relatively distinct patches. These patches should be monitored/mapped to determine if they are expanding or shrinking. If monitoring reveals expansion, use of the herbicide Plateau is recommended in conjunction with spot reseeding. It is possible this activity could occur as a normal range management practice without resetting the clock. At present, WP008 is a good example of an improved pasture grassland community that would contribute to the local system as foraging habitat for wildlife (especially elk), as well as provide a variety of management opportunities for livestock grazing. Rio Tinto Energy America/Coloveyo Mine Page 26 Revegetation Monitoring - 2007 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • r • • •