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<br />3 <br /> <br />14.6 cm). The study site is located on Yamac loams (fine-loamy <br />mixed, Borollic Camborthids), which support a big sagebrush- <br />wheatgrass-junegrass community (Redente et al. 1985). <br />In the summer of 1984 the existing vegetation and the top 5 cm <br />of topsoil were removed by scraping with a bulldozer and the next <br />35 cm of soil was mixed with a motorgrader. This disturbance was <br />used to simulate disturbances associated with energy development <br />and commonly found throughout the Colorado Plateau. The <br />disturbance led to a 90$ reduction in soil seed bank (Carpenter et <br />al. 1990) , and to further reduce the seed bank, the plots were <br />weeded by hand for two years following disturbance. In November <br />1987 the plots were seeded with a mixture of species characteristic <br />of both early- and late-seral stages at the site to minimize the <br />effect of migration as a possible factor in the early seral <br />dynamics on the plots. <br />The experiment was arranged in a factorial design with four <br />blocks, each block containing three 160-mz treatment plots. The <br />three treatments were randomly assigned to plots within each block <br />and consisted of: <br />1. Control - disturbed, weeded, and seeded, but with no <br />additions. <br />2. Nitrogen - disturbed, weeded, seeded, and fertilized with <br />ammonium nitrate at 100 kg N/ha/yr. <br />3. Sucrose -disturbed, weeded, seeded, and sucrose added <br />at a rate of 1600 kg C/ha/yr. <br />