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4.3 HERBACEOUS PRODUCTION <br />Mean herbaceous production ranged from 94.11 g/mZ (1998 reseeded or interseeded azeas) to <br />. 117.80 g/m2 (Osgood sand reference azea). The Osgood sand reference area showed a <br />significant increase of 106.8% from 2004. The 1998 reseeded or interseeded azeas showed a <br />45.4 percent decrease in production from 2004 despite an overall increase in precipitation for <br />2005. The 1999 reclamation areas were relatively consistent between 2004 (110.05 g/mZ) <br />and 2005 (107.11 g(m2). <br />Herbaceous production varies significantly from yeaz to yeaz. In the Osgood sand reference <br />azea herbaceous production increased along with the precipitation increase in 2005. <br />Production decreased in the 1998 reseeded or interseeded azeas and remained relatively <br />consistent in the 1999 reclamation azeas from 2004 to 2005. <br />Table 15 shows a comparison of total herbaceous production values for the Osgood sand <br />reference azea, the 1998 reseeded or interseeded areas, and the 1999 reclamation areas for the <br />last two growing seasons. Additionally, the major species contributing significantly to <br />relative vegetation cover have been entered by yeaz and area. While other factors (such as <br />overall physiognomy) affect the relationship between species cover and production, this <br />comparison is useful to illustrate a relationship between precipitation distribution over the <br />growing season, species seasonality, and herbaceous production. <br />While the 2004 growing season precipitation amount (September 2003 to July 2004) was <br />below average, there were no significant spikes in precipitation during individual months that <br />would promote differential growth in cool or warm season species. Representation in <br />herbaceous production for 2004 is indicative of this across the azeas sampled; Bromus <br />tectorum is the major contributor to annual grass production, a mix of cool and warm season <br />grasses contribute to the perennial grass production, and Helianthus annuus and Kochia <br />scoparia are the major contributors to forb production. <br />During the 2005 growing season, with the significant pulses of precipitation in April and <br />June, changes in the overall contributions of individual species may explain lower total <br />herbaceous production levels in the reclamation azeas. Major biomass contributors in the <br />Osgood sand reference area remained the same in 2005, Bromus tectorum and Stipa viridula, <br />both cool season graminoids benefiting from spring moisture pulses. Increases in total <br />herbaceous production in annual and perennial grasses this year at the reference area can be <br />explained by increased growth in these two species this year. <br />In the 1998 reseeded or interseeded areas Bromus tectorum remained the major annual grass <br />contributing to production, benefiting significantly from the precipitation distribution this <br />yeaz (reflected in the increase in total herbaceous production by annual grasses this yeaz). In <br />2004, Catamovilfa tongifolia and Agropyron smithii were the major biomass contributors (a <br />warm season and a cool season grass), while this season only warn season grasses were <br />major contributors (Calamovilfa longifolia, Bouteloua gracilis, and Andropogon hallii), <br />providing an explanation for decreased total herbaceous production as these species did not <br />receive the benefit of summer precipitation to achieve maximum growth by the time of <br />Coors Energy Company Keenesburg Mine Page 23 <br />2005 Revegetation Monitoring Report <br />