2017-05-11_PERMIT FILE - C1981012 (13)

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56 ' the soil nitrogen supply. On treatments receiving nitrogen fertilizer, the material now in its fourth year following application is probably starting to be leached of nitrogen down and away.from the plants due to the coarse nature of the spoils (Table 1). With a small legume component on these nitrogen added sites, due to inhabition during the establishment period, there is now less total nitrogen available to the grasses for their growth. Hence, this extra nitrogen source on Treatment 2 favors the'growth of seven grass species; in particular intermediate and western wheatgrasses produce at a rate approxi- mately double that found on the Main Plot as a whole (Table 14). Highest combined seeded and invading density was on Treatment 3 (Figure 12). Density of invading forbs was extremely high compared to other treatments, but the biomass of these was relatively low. Examination of the data showed Treatment 3, Replication 3, to have a very high density of kochia • seedlings in one of its quadrats (880 plants/m2). These results suggest that a mature kochia plant, laden with seed, may have blown into the plot sometime between fall 1919 and spring 1980. Given the localized nature of this occur- rence it appears that Treatment 3's density level is actually much closer to that found in other treatments. Seeded grasses occurred at a significantly higher density on mulched treatments versus those unmulched; thus, while mulching does not increase plant vigor, it does suggest the benefit of this material to aid plant establishment. One word of caution: by favoring the establishment of grasses one runs the risk of eliminating what few shrubs might have grown due to an inability to compete with the rapidly growing grasses (Figures 10-12). The result is a less diverse plant community. • A final comment on the performance of the Main Plot treatments warrants mentioning. Considering the data in Figures 10-12, there are approximately e