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sample mean parameter values assume that the sample mean value accurately represents the population mean in all cases. • SPECIES IDENTIFICATION AND VERIFICATION Species identification was accomplished in the field through the use of plant identification keys (Harrington, 1954, Weber, 1990; Whitson, 1987; Zimdahl, 1990, Stubbendieck, et al, 1995). In cases where plant identification was inconclusive in the field, voucher specimens were pressed for lab identification. III. RESULTS Calendar yeaz 2002 precipitation levels were the lowest in the last decade. Precipitation was significantly below the ] 0-yeaz monthly means in nine of the twelve months, with precipitation significantly below normal from April through September. Total precipitation for 2002 was 7.77 inches. Cumulative precipitation for the January-July 2002 period was 4.28 inches. Total cumulative precipitation for the period from September 2001-July 2002 was 6.46 inches. This represents a 39 percent decrease from the yearly precipitation mean, a 49 percent decrease from the January-July average of 8.43 inches, a 43 percent decrease from the September-July average, and a 66 percent (January-July) and 59 percent (September-July) decrease from the corresponding periods in 2001. • QUANTITATIVE EVALUATION: REFERENCE AND RECLAMATION AREAS OSGOOD SAND REFERENCE AREA The Osgood sand reference area represents approximately 3.4 acres of undisturbed native vegetation within the Keenesburg Mine permit azea. The reference azea is sited immediately west of the mine access road and has been fenced to prevent grazing by domesticated livestock. The reference azea is flat and exhibits sheet flow drainage to the east-southeast. Soils aze generally sandy in texture, with little incorporated organic matter. The vegetation community was visually dominated by the woody shrub Artemisia filifolia (sand sage), and cool season graminoid Stipa viridula (green needlegrass). Three warm season grasses were also common within the reference area, Bouteloua gracilis (blue grams), Calamovilfa longifolia (prairie sandreed), and Andropogon hallii (sand bluestem). Bromus tectorum, an annual undesirable grass was not present in significant numbers within the reference area this growing season. Four forb species were encountered during cover sampling this growing season. The number of species represented in cover sampling decreased from seventeen in 2001 to twelve this yeaz (Table 1) (Savage and Savage, 2001). Specific sampling information for the reference azea is contained in Tables 2 and 3. I • Coors Energy Comparry Page 5 2002 Revegetatfon Monitoring Report