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• <br />• <br />• <br />2.9 Planted Seed Establishment <br />Perusal of Table 19 indicates two indicators of seeding success. The first is the overall seeding <br />success rate or percent cover of seeded species divided by total percent plant cover. This indicator <br />averaged 38.4% for the 1999 revegetation and 18.3% for the 2002 revegetation. These values are in <br />line with expectation given the ages of the two groups of revegetation. If annual bromes or other weedy <br />taxa were overly problematic, the seeding success (ground cover) rates would diminish with age. <br />The second indicator of seeding success is the "relative success" by species determined for each <br />year by dividing the percent of the seed base attributable to each species (based on number of seeds <br />planted) into the resulting percent ground cover documented by point-intercept sampling (Table 18 and <br />Charts 17 - 19). For example, if species Z comprised 10°k of the total number of seeds planted and then <br />exhibited 20% of the resulting ground cover, a relative success of 200% would be realized (20/10). <br />Similarly, if species Y comprised 10% of the total number of seeds planted but only exhibited s% of the <br />resulting ground cover, relative success of 50% would be realized (5/10). <br />Given this type of analysis, it has been Cedar Creek's experience that grass species exhibiting <br />between 20% and 200% relative success are typically appropriate for the seed mix and are being planted <br />at appropriate rates. Taxa with less than 20% relative success may need assistance through special <br />handling (e.g., boosting the amount of seed in the mixture or adding an appropriate fertilizer or <br />supplement), or are candidates for deletion or substitution. Taxa with more than 200% relative success <br />should be re-evaluated for possible reduction of the amount of seed planted. Elevated success rates are <br />often indicative of over aggressive taxa that can be detrimental to the overall community diversity, <br />Furthermore, decisions regarding seed mix manipulations should be based on multiple years of analysis <br />owing to climatic and other influences that occur annually. <br />Similar "boundary" values for fortis would be 5% and 150%. Forb populations typically require far <br />more seed to establish even minimal cover values, and most often, grass taxa are too competitive for all <br />but the most aggressive forb species such as adapted introduced plants like alfalfa, sanfoin, and titer <br />• milkvetch. Finally, "boundary" values for shrubs in young reclamation would be 2% and 200% with the <br />• exception of sagebrush where the low-end success rate of 0.5% can be considered acceptable (owing to <br />• the small size of planted seed). <br />• Rio Tinto En°rgy America / Colowyo Mine Page 65 Revegetation Monitoring - 2006 <br />