On clay soils, Russian knapweed dominated quickly but on clay loam soils, grass biomass remained higher through time and it took longer for Russian knapweed to dominate. On loam soils, Russian knapweed never became dominant. Percent Russian knapweed aboveground biomass from the last 50 years of the simulations was chosen as an index of knapweed success. The relationship between this value, mean annual temperature and precipitation was used to extrapolate simulation results across the state. The most vulnerable areas of Colorado corresponded closely to those that are known to be infested with Russian knapweed.
Results show that N mineralization and plant available N in the soil decreased after invasion.
The pulse likely is due to high inputs of plant litter and roots from cultivation. Results indicate the importance of Russian knapweed to soil N dynamics, and that supplemental N may be as effective as cultivation during restoration. Publications Beck, K. G. and J. R. Sebastian. 1993. An integrated management system for Canada thistle in pastures. Beck, K. G. and J. R. Sebastian.