2008-12-22_REPORT - C1980001 (3)

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2006 Edna Mine Vegetation Sampling Report 5. West Ridge & Moffat Non-Topsoiled BRU The West Ridge & Moffat Non-Topsoiled BRU encompasses approximately 224 acres. Sample adequacy for vegetation cover was obtained in this unit with 30 transects. Mean vegetation cover was 30.5 %. This is a decrease of more than 11 percentage points from the mean cover in 2005 (41.6%). (Note that for non-topsoiled areas, total vegetation cover is used, not just herbaceous cover.) The t-test utilized by Colorado DRMS requires that the reclamation mean is at least 90% of the technical standard. For this unit, the technical standard for vegetation cover is 47%, and 90% of this standard is 42.3%. The t-test indicates the mean of the reclamation does not meet the standard for vegetation cover (Table 5-2). A large portion of the 11 percentage point decline in total vegetative cover from 2005 can be attributed to the decrease by almost 9 percentage points of introduced biennial forbs, primarily yellow and white sweet clover (Melilotus officinalis and M. alba). This may be attributable to the biennial nature of the two species, or possibly the lack of early season moisture prevented germination of sweet clover seeds or re-emergence of the previous year's species. It also appears that perennial introduced grasses and forbs replaced perennial native grasses that were present last year. In addition, there was a decrease in native shrubs. It is possible that the shrubs and native grasses did not have adequate early season moisture to emerge from dormancy and may have either remained dormant, or did not survive, while introduced species were able to take advantage of late-season moisture to thrive. Also, whether or not these trends are real and the nature of their amplitude is unknown, since the cover data is "first-hit cover" and may mask understory cover located below the primary intercepts. Although the total vegetation cover did not meet the technical vegetation cover standard this year, the herbaceous vegetation cover (28.5%) of this unit did exceed the 24.1% herbaceous cover of the reference areas (t=3.09, df=29). This implies that reclaimed herbaceous vegetation has responded to weather patterns similarly to nearby undisturbed areas. It should be noted that the plant species present within this reclaimed area are cool-season species that typically realize about 67% of their normal seasonal growth in the spring and early summer, with about 33% being realized in the fall. It would be prudent to adjust the technical standard for this lack of rainfall in the spring growth period for the 2006 vegetation monitoring data. A voluntary diversity goal for this unit was established as 90% graminoids, 5% forbs, and 5% trees/shrubs. The actual diversity in this unit in 2006 was 42.7% graminoids, 50.5% forbs, and 6.8% shrubs. While the percentage of grass cover is lower than the voluntary goal, the permit states that P&M desired to maintain the percentage of grasses below 90% to allow for the expression of forbs and shrubs. In addition, the desired goal was to increase the diversity of grass species present to between 5 and 15 native species. Six native grass species were present this year, which made up about half of graminoid cover. The other half was comprised almost entirely of the introduced orchard grass (Dactylis glomerate). See Table 5-3 and Table 5-4 for absolute and relative cover data for this unit. 5.1. Supporting Documentation Tables 5-1 through 5-4 summarize vegetation data and statistical tests for the West Ridge & Moffat Non-Topsoiled BRU. Table 5-5 provides a list of the community plant species sampled Habitat Management, Inc. 51 October 19, 2006