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<br /> <br />significantly between these two species within any of the three <br />treatments. The two intermediate seral herbaceous species (As e <br />canescens and Aaroovron smithii) displayed patterns similar to each <br />other but different from the early-seral response pattern. <br />Nitrogen concentration increased in the intermediate-seral specie6 <br />between sucrose and N treatments, but not between sucrose and <br />control treatments. Also, the N concentrations increased much lass <br />between sucrose and N treatments than with the early-seral species <br />(25-50$ and 100-150$ respectively). Nitrogen concentration in the <br />species occurring last in the seral gradient, Chrvsothamnue <br />was not influenced by treatment and, of the five major <br />species, had the highest N concentration under the low-available N <br />(sucrose) treatment. <br />Secondary succession patterns following the type of <br />disturbance used in this study have been reported for the study <br />site (McLendon and Redente 1991). Control plots are dominated by <br />an annual-forb community for the first two years and the annual <br />grass Bromus tectorum becomes an important component the third <br />year. Perennials slowly increase from the first year, with <br />perennial fortis becoming important by the third year, perennial <br />grasses the fourth year, and shrubs by the fifth year. This <br />pattern is modified by N addition. Annuals, primarily Kochia <br />scooaria, continue to dominate plots receiving additional N through <br />the fifth year, with perennials present but only in small amounts, <br />