2010-03-12_REPORT - C1981019 (8)

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sagebrush where the low-end success rate of 0.5% can be considered acceptable (owing to the small size of planted seed). There are distinct differences between the seed mixes used on the Section 16 Year 10 area and the East Pit Area. The main difference is that the 1999 seed mix (S16 Year 10) used more introduced species, especially grasses. All of the non-native grass species had been removed by 2002, therefore the seven year old and younger revegetation was subject to the newer seed mix with all native grasses. However, there are still a couple of non-native forb species (sainfoin and cicer milkvetch) in the newer seed mix due to their relative success. Because the seed mix used on Section 16 Year 10 is no longer being used, no analyses are necessary. Therefore, comments on species specifics will be limited to the current seed mix. On a species-specific basis, excellent relative success was obtained for western wheatgrass and streambank wheatgrass. Good to fair performance was observed for mountain brome basin wildrye, slender wheatgrass, beardless bluebunch wheatgrass, Lewis flax, Western yarrow, Wood's rose and big sagebrush. A few species exhibited excessive dominance and seeding rates may need to be adjusted to accommodate for performance; those plants were thickspike wheatgrass, and cicer milkvetch. The remaining species exhibited poor relative success and should be re-evaluated or considered for elimination / substitution. Among taxa to be considered for elimination from grassland targeted mixes are: sainfoin, Palmer penstemon, Sandberg bluegrass, Rocky Mountain fescue, four-wing saltbush, Louisiana sage, Pacific aster, Rocky Mountain penstemon, serviceberry, silver sage, winterfat, rubber rabbitbrush, antelope bitterbrush, mountain snowberry, and fringed sage. Approval of TR-72 has changed the seed mixes used on Colowyo reclamation, therefore it will be important to evaluate the seeding success of those first units seeded with the new mixes. Early evaluation of seeding success will allow for minor changes to seed mixes to maximize opportunities for future seeding success. 2.6 CSU Shrub Plots In the Fall of 2000, the Colorado Division of Minerals and Geology (CDMG - now CDRMS) and Colorado State University (CSU) designed and established a group of Shrub Establishment Plots to aid in the reclamation and revegetation planning at Colowyo. Historically, shrub establishment on revegetation at the Colowyo Mine has been largely unsuccessful due to two limiting factors: browsing by elk and deer, and competition from aggressive grasses. Ten demonstration plots (five fenced and five unfenced) were established to observe how much of an effect these limiting factors play in the eventual composition of the revegetation. To demonstrate the effects of ungulate grazing, a 2.7 acre area of reclamation (test plots) was fenced in the spring of 2002 to exclude elk and deer, while the remaining 4.7 acres was left unfenced (see Map 4). The five different treatments within this study area were as follows: CEDAR CREEK ASSOCIATES, Inc. Page 31 Colowyo Mine 2009 Revegetation Monitoring Report