2008-02-28_REPORT - C1981028 - Laserfiche WebLink

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significantly dry year to an average year with a heavy pulse of moisture at the beginning of the growing season. Based on this, several general observations can be made regazding species representation and relative cover this season. The May 2007 precipitation encouraged growth in the annual cool season graminoid and forb component, as evidenced by lazge increases in relative cover from 2006-2007 by Bromus tectorum and Sisymbrium altissimum. Where present (1998 areas), the cool season perennial grass Stipa viridula showed significant representation this yeaz. The average moisture accumulations through the growing season (coupled with the significant May moisture) contributed to significant growth in the perennial warm season grasses (Andropogon hallii in the 1998 and 1999 azeas, Andropogon gerardii (big bluegrass) in the 2000 azeas, Calamovilfa longifolia in the 1999 and 2000 areas, and Bouteloua gracilis in the 1998 areas) and warm season forb Helianthus annuus (1998 and 2000 azeas). Of the species encountered for several years in the reclamation areas, only a few appeaz to be predictably correlated with regazd to relative cover and precipitation. Bouteloua gracilis, while of small stature and therefore overshadowed by larger species, consistently provides greater relative cover in years with average or above average precipitation. Bromus tectorum responds significantly to mid to late spring pulses of precipitation, as evidenced this year. Calamovilfa longifolia, once established, is consistently present as a dominant in the reclamation areas, yet provides more relative cover during drier years, especially with aging in the stands. Helianthus annuus is usually present in the reclamation areas, benefiting from precipitation throughout the summer. This species appears to be an opportunistic species, and significant growth occurs whenever soil moisture is present and competition from mature graminoids is low. Kochia scoparia responds inversely to the amount of precipitation. It prefers drier conditions, and relative cover is greatest during dry years. This maybe an artifact of reduced representation (or competition) by other species during wetter years. Variation in mean total vegetation cover in the reclamation azeas (Table 9.) was 11.8 percent in 2007 (if the 2002 reclamation azeas are excluded, the total variation is only 4.8%). Total vegetation cover within the reclamation areas ranged from 45.60 percent (2002 reclamation areas) to 57.40 percent (2000 reclamation azeas). Sample adequacy with ten samples was achieved in all reclamation area sampling. 43 HERBACEOUS PRODUCTION Mean herbaceous production ranged from 99.87 g/m2 (2002 reclamation azeas) to 150.84 g/m2 (1999 reclamation areas). A decrease in total herbaceous production occurred in the 1998 reseeded or interseeded areas and the 2000 and 2002 reclamation azeas from 2006 to 2007, ranging in magnitude from four to 28 percent. Increases of 17 and 26 percent in total herbaceous production from last yeaz took place in the 1999 and 2003 reclamation azeas, respectively. These modest increases and decreases in total herbaceous production were hypothesized to correspond to increased growth by annual grass and forb species, out- competing perennial species from resources while producing less overall biomass. This continues to affirm the observation that distribution of precipitation at certain critical growing season periods significantly affects biomass production and species contributions at the Keenesburg Mine. Coors Energy Company Keenesburg Mine Page 21 2007 Revegetation Monitoring Report