2010-07-15_REPORT - M1988044 (2)

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grasses, forbs, and shrubs resulting in a more rapid advancement to a growth dominated by perennials rather than annuals. This is also the reason why adding fertilizer at the time of seeding is not a good practice unless there is a very good reason for doing that. All the revegetation areas are continuing to be amazingly free of noxious weeds, for the most part, although annual weeds can still be common in some of the younger growth areas. The invasion of Tamarix detected in 2006 has largely been controlled with continued clean up of a few remaining plants. As a result of good moisture the last couple of years, Canada thistle has shown a tremendous increase in growth vigor and has expanded to some revegetation areas. This species has now been shifted to top priority in the weed control program and heavy control efforts are being implemented this year. The increased moisture has continued to benefit the undisturbed grasslands as well as the lowland areas. Much of the beneficial effects of removing grazing appear to have run their course at this point with only limited gains expected in the future. Density is continuing to increase as well as productivity and now needlegrass is showing signs of becoming a dominant in the vegetation structure. It still has a ways to go to achieve the kind of dominance expected in some classifications and descriptions of this vegetation, but the development certainly seems to be headed in that direction. Blue grama in most upland areas is still very strong, but there appears to be a shift in the species composition more toward the needlegrass and even some bluestems. Weed density (mainly spurge and cheatgrass), although still high, is much reduced in most areas as a result of the heavily grazed native grasses coming back with strong growth in the last few years. Because there is no quantitative data that defines the species frequency distribution during grazing or after, it is hard to say whether the apparent shift in the species is real or an illusion caused by just robust plants providing a visual dominance that may or may not be reflected in a numerical dominance. One thing is clear, though, and that is the productivity of the grasslands as a whole has increased remarkably since the removal of grazing and appears to be shifting back somewhat more toward a needlegrass-wheatgrass-bluestem-grama grassland. It is still most likely this development pattern is more a result of the removal of grazing which was utilizing certain grasses to an excessive extent. It is unlikely that over such a short period of time there has been a great deal of real change in the species frequency distribution curves. Nevertheless and irrespective of the details of the dynamics that are actually occurring, the changes are definitely beneficial and appear to be headed in the right direction. It is important to note that in the 2007 planted areas, one of the most successful species was needlegrass with western wheatgrass and/or blue grama hanging on to a distant second place. This is important because as the undisturbed (by mining) grasslands begin to shift more toward a needlegrass dominance with wheatgrass and grama subdominants, the revegetation areas seem to be also trending in that direction. In time, this should allow a closer compatibility in the species structure between revegetated areas and undisturbed areas. It will take many years for that to fully develop, but so long as the structure of these two vegetation units continue to trend toward structural convergence then eventually the reclamation should be indistinguishable from the natural vegetation. The five new exclosures were quantitatively sampled in early fall of 2009. Analysis of the data and comparison to previous data showed significant gains in growth. The protection of the trees has reaped considerable benefit with woody biomass continuing to increase. The large gains in 2007 and 2008 were not generally seen in most areas due to the growths reaching what appears to be a density restricted plateau. Until density declines through environmental selection, rapid gains in height will be limited to areas where the density restricted plateau has not been reached. Status report for 2009 due July 15, 2010 Page 2 of 11