2011-01-19_REVISION - C1981019 (5)

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PO ,Jennifer Sekulski-Barton e Colowyo Coal Company MW. ' 5731 State Highway 13 Meeker, CO 81641 T: 970-824-1529 Mo+• Z both within the "academic" scientific community as well as the "applied" 0 revegetation science community. • The majority of individual shrubs and trees within the identified patches of the BRB 79-95 were at least 11 years of age (2006 minus 1995) and therefore were classed "mature" excepting certain tree species that would fall within the "young" class. Both of these groups consist of plants that have stabilized, are persistent, are readily visible, and exhibit low rates of mortality. • Over the course of sampling for ground cover and production during 2007, a majority of shrub patches totally enumerated in 2006 were reviewed by field personnel to verify: 1) that no catastrophic events had occurred, and 2) that the readily observable mature age class appeared consistent and "on par" with the prior year's enumeration. • The standard of 150 plants per acre yields a success criterion (90% of the standard) of 135 plants per acre. The enumerated population resulted in an average of 411 plants per acre. Therefore, the population as of 2006 was 304% greater than the success criterion. In the absence of catastrophe, it is improbable that an established and persistent, mature stand of shrubs that has survived for at least 11 years would drop so precipitously as to then fail comparison with the success criterion. • Approximately one-half of the acreage of shrub patches occurs within fenced enclosures thereby providing some level of additional protection from mortality due to excessive herbivory. • Nearly all shrub patches exhibit a population of rhizomatous shrub species (e.g., rose and snowberry) that tend to expand their population densities even under the competitive pressure of herbaceous taxa and/or grazing and browsing pressure. • Finally, shrub patches were totally enumerated in 2006 to eliminate the complications resulting from sampling error, especially given the excessive variation associated with the woody plant density variable. Typically, the primary (but small) error that occurs under total enumeration involves the seedling age class of shrub species. This group, along with other, low- profile shrub taxa (e.g., rose and snowberry) occasionally remain undetected given thick stands of herbaceous life forms. As a result, total counts err on the low side given the typically modest underestimations.