| Abstract
| - Across western North America, invasive plant species and elevated levels of nitrogen are threatening the productivity of rangelands. A bioeconomic model of stocking cattle on these rangelands is used to show that optimal stocking depends on the competition between native grasses and the invaders. However, nitrogen deposition is important in determining the ultimate rangeland species composition. Endogenous changes in plant successional thresholds are due to the interplay of nitrogen deposition and stocking practices. Nonoptimal overstocking can create ecosystem niches for invaders where they would not have occurred at lower stocking rates, although what constitutes overstocking depends on the nitrogen levels.
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