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Woody Plant Density <br />. ~ BACKGROUND DENSITY <br />2006 data from the 2002 reclaimed area estimate the density of woody plants at 138 stems per <br />acre, and thus a rise of more than 10x in woody plant density has occurred from the two-year old <br />stage to the 4-year old stage (see ESCO 2005). Between 2004 and 2006, big sagebrush <br />proliferation accounted for this increase. This trend suggests that the 200 stems per acre <br />background standard should be attainable by time Phase III bond release evaluation is <br />appropriate (another six years). <br />In the 2004 reclamation area, the 2006-observed woody plant density level of 328 stems per acre <br />is very encouraging for such young revegetation. Comprising this total are big sagebrush, <br />mountain snowberry, serviceberry, and chokecherry, some of which may have come from nursery <br />stock plantings as did all of the aspen present. However, at least some of the four shrub species <br />may well have developed from seeding. <br />Species Diversity and Composition <br />The data illustrated in Figure 5 show that the 2002 reclamation (the oldest) has, by a slight <br />amount, the greatest amount on annual/biennial plant cover and defying the general pattern that <br />the proportion of vegetation cover comprised of these plants is distinctly less as reclamation age <br />increases. This is thought to relate to the fact that 2002 was an extremely dry year and there was <br />little winter soil moisture carry-over support, and the opportunistic annuals took advantage of <br />spring 2003 moisture better than seeded perennials could. As a result the establishment of <br />competing perennial cover had a weak start in these areas. <br />The distribution of species density by lifeform (Figure 4) shows that the 2002 and 2004 reclaimed <br />areas are more similar to the reference areas than would appear to be the case from the lifeform <br />distribution of relative cover (Figure 5). This is important in that it shows that the basic <br />components of the original ecosystem have indeed been returned and that it is a matter of <br />relative proportions of species (and age or community successional status) that separates the <br />reclaimed from the native vegetation. Perhaps the largest difference with regard to species <br />density is in the native perennial (orbs category, where native areas (at least the most extensive <br />native types of Mountain Brush and Sagebrush) tend to have half again to twice as many species <br />of native perennial (orbs per 100 sq.m. Data for total native species density in the 2002 <br />reclamation areas was 19.6 species per 100 sq.m. in 2006, up six species per 100 sq.m. since <br />year 2004 (13.5 species per 100 sq.m.; ESCO 2005). Average total species density on the <br />reclaimed areas exceeds that of all reference areas (Figure 4). Even if one discounts the <br />. additional annual and biennial species in these reclaimed areas, the average total species density <br />equals or exceeds that of any of the reference areas. <br />16 <br />