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34 <br />cultural practices. Grasses showed no marked preference for any treatment, <br />fora variety of reasons as discussed below. Nitrogen applications would be <br />expected to stimulate grass production. Instead, rapidly growing forbs like <br />Palmer penstemon, Lewis flax, and titer milkvetch outcompeted the grasses for <br />nitrogen on the excelsior plots while shrubs and forbs combined to suppress <br />them on Treatments 3 and 4 (Figures 6 and 7). The moisture holding capacity of <br />the mulch helped the forbs to become established along with the grasses. In <br />time however, due to the very deep rooted characteristics of forbs, they are <br />beginning to outcompete grasses because of their ability to utilize deeper <br />moisture and nutrient reserves. The greater vigor of forbs and shrubs when <br />viewed against grass growth on Treatments 3 and 4 was the result of those <br />factors outlined above, i.e., rooting nature of the life forms and leaching of <br />nitrogen to depths unobtainable by grass root systems. There is one reason <br />responsible for the difference in the species composition between mulched and <br />unmulched nitrogen amended treatments however; the lack of mulch reduced forb <br />establishment which subsequently removed some of tire potential competition on <br />slower growing shrubs and thereby allowed them to fill a more dominant niche <br />in the community. <br />The low production of grasses on Treatment 2 is directly related to <br />nitrogen being withheld and good growth of nitrogen-fixing legumes such as <br />alfalfa, titer milkvetch, and yellow sweetclover. These nitrogen-fixers find <br />a competitive edge on the phosphorus amended treatments (an element essential <br />for NZ fixation) where they are not limited by a lack of nitrogen nor must <br />they rival more rapidly developing plants that would edge them out on nitrogen <br />fetilized sites. <br />To conclude, the Control produces a stand of vegetation characterized by <br />a growth response two to six times lower than that found in other treatments. <br />Treatments 2-6 support similar levels of plant vigor, but with one main <br />