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Figure 6 - Beltline Reference Area #3 <br />Noxious Species Densities <br />-• <br />1998 1999 2000 2001 <br />—0--- Thistles per <br />sq. meter <br />• Ox -eye daisy <br />per sq. meter <br />2001 noxious weed density data is presented in Table 11. Table 12 lists density sample means for noxious <br />thistles, oxeye daisy, and noxious species combined, for each year of the study. <br />Reference Area No. 4 <br />Figure 7 depicts the dramatic initial decline in noxious species cover observed at the beltline outslope <br />between 1998 and 1999. In 1998, the density of noxious weeds was so great that a density count was not <br />attempted. Absolute cover of noxious species declined from 41.0% in 1998 to 1.0% in 1999, and has <br />remained low (2.0% in 2001). In 1998, two species accounted for the bulk of the noxious cover; oxeye <br />daisy (21 %) and plumeless thistle (16 %). In 2001, these were the only two noxious species sampled, each <br />contributing 1.0% cover. Canada thistle was a minor component of the stand each year, contributing 2% <br />absolute cover in 1998 and 3% absolute cover in 2000. <br />80.0% <br />70.0% <br />60.0% <br />50.0% <br />40.0% <br />30.0% <br />20.0% <br />10.0% <br />0.0% <br />Figure 7 - Beltline Reference Area #4 Absolute <br />Cover Trends; 1998 -2001 <br />1998 1999 2000 2001 <br />Total Vegetation <br />Cover <br />=Noxious Cover <br />—* —Grass Cover <br />— <br />+ —Non- Noxious Forb <br />Cover <br />—w--Shrub Cover <br />2001 absolute and relative cover by species and category is presented in Table 13. Table 14 presents <br />absolute and relative cover sample means by category for each year of the study. As illustrated in Figure 7, <br />the most sharply defined responses are the dramatic decline in noxious species cover, and the contrasting <br />increase in grass cover (from 10.0% in 1998 to 36% in 2001). A number of grasses contributed to the <br />7 <br />