2011-02-28_REPORT - C1981028 (5)

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• Plant Species Relative Cover 2009(%) Relative Cover 2010(%) % Relative Cover Change 2009-2010 Bromus tectorum 9.28 40.30 (+)334 Calamovil a lon ' olia 4.35 12.73 (+)192 Bouteloua acilis 0.00 4.85 (+)100 Si brium altissimum 0.87 1.52 (+)75 Medico o lu lina 0.58 0.61 (+)5 Melilotus o Icinalis 4.06 4.24 (+)4 Ambrosia silostach a 1.16 0.91 (-)22 O zo sis h enoides 66.09 32.12 (-)51 A o on track caulum 6.38 2.12 (-)67 Era ostis cilianensis 1.16 0.30 (-)74 Panicum vir arum 2.61 0.30 (-)88 Helianthus annuus 1.16 0.00 (-)100 Kochia sco aria 0.87 0.00 (-)100 Schizach ium sco arium 0.58 0.00 (-)100 Bouteloua curb endula 0.29 0.00 (-)100 Bromus mar 'natus 0.29 0.00 (-)100 Ratibida column era 0.29 0.00 (-)100 Changes in relative cover on a yearly basis may not reflect long term trends but should reveal 0 individual species responses to precipitation distribution and competition from other species. The changes in relative cover from 2009-2010 reveal changes in species representation where above average spring precipitation and a lack of mid-growing season precipitation occur. Significant increases in relative cover occurred between 2009 and 2010 for one cool season annual grass, two perennial warm season grasses, and one annual forb. Minor increases in relative cover were found for one annual and one biennial forb. The significant increase in relative cover for Bromus tectorum is easily explained by the perfect seasonal growing conditions for this cool season annual. Though the seasonal precipitation regime did not favor warm season species (three of four encountered in 2009 were not sampled in 2010), one warm season species (Calamovilfa longifolia) significantly increased in relative cover, and another (Bouteloua gracilis) was sampled for the first time. It is deduced that the relative cover increases in these species is due to their morphology; Calamovi fa longifolia is a large tall graminoid, more likely to be encountered when overall vegetation cover is lower. Bouteloua gracilis is also likely to be sampled more when overall vegetation cover is lower, as competitive vegetation cover near the ground (Bouteloua being generally shorter in stature than most plants in the revegetated areas) is less. Remaining species sampled in either 2009 and/or 2010 revealed significant decreases in relative cover. Six species were not sampled in 2010; including two native warm season grasses, two warm season forbs, one cool season native perennial grass, and one warm season annual forb. Two cool season perennial grasses (Agropyron trachycaulum and Oryzopsis hymenoides) revealed significant deceases in relative cover this season. Whether this is Coors Energy Company Keenesburg Mine Page 13 2010 Revegetation Monitoring Report