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z 2 <br />nmin = (t )w <br />(d Xbaz)2 <br />where : <br />nmin = minimum sample size <br />t = the "T" distribution value at the 90% confidence level <br />s = sample standard deviation <br />s2 = sample variance <br />d = percent acceptable deviation from the mean (10%) <br />Xbar = sample mean <br />2007 Results <br />Precipitation in 2007 was unusually high during the winter and spring. Data from the <br />Arkansas River Basin show that the precipitation from January through June 2007 <br />was 7.83 inches. This regionally high precipitation is reflected in the cover and <br />production values obtained from the reclaimed areas. <br />A total of 29 transects were sampled: twelve on Pit 4; thirteen on the large Pit 2 <br />contour strip east of the county road; and four on the small Pit 2 contour strip west of <br />the county road. After calculating sample adequacy it was determined that 10 <br />samples were adequate for cover and 28 samples were needed to achieve production <br />sample adequacy. Therefore, sample adequacy was achieved for both cover and <br />production. <br />2007 Cover <br />The average total vegetation cover in 2007 was 44.8%. Of this total, grasses <br />contributed 17.1%, forbs contributed 24.5%, sub-shrubs contributed 1.7%, and <br />shrubs contributed 1.6%. The predominant species was smooth brome, an introduced <br />grass, at 13.8% absolute cover and a relative cover value of 30.7%. Field bindweed <br />was the second most dominant species with 11.2% absolute cover and 25.0% relative <br />cover. Alfalfa contributed 3.9% absolute cover and 8.8% relative cover followed <br />closely by sweet clover at 3.1 % absolute cover and 7.0% relative cover. In 2007, 32 <br />species were observed in the cover sampling as shown on the species list in Table 3. <br />2007 Species Composition <br />The total number of plant species encountered during cover sampling was thirty-two. <br />Graminoids accounted for eight species, forbs - twenty species, sub-shrubs - one <br />species and shrubs - three species. Some of these could not be identified in the field. <br />Of the identified species twelve were native and fifteen were introduced. A mix of <br />annual and perennial species was present. There were sixteen perennials, five <br />biennials and eight annual species observed. Seasonality of the reclaimed area <br />species was mixed, both warm and cool season species were present, however only <br />1.8% of the relative cover was composed of warm season grasses and forbs. Cool <br />16