Dodson, Erich.  2004.  Monitoring change in exotic plant abundance after fuel reduction/restoration treatments in ponderosa pine forests of Western Montana.  M.S. Thesis.  The University of Montana.  95 pages.

In lowland fire adapted forests of the inland Northwest, restoration treatments (mechanical thinning and/or prescribed burning) are used by forest managers to restore structure and function to forest stands and reduce the risk of stand replacing wildfire.  Such treatments generate disturbances that may have the potential to facilitate invasion by exotic plant species.

The Lubrecht Fire/Fire Surrogate site is located in western Montana, on the University of Montana’s Lubrecht Experimental Forest in ponderosa pine/Douglas-fir forest.  Exotic species richness, frequency, and cover were monitored at multiple spatial scales (1 m², 100 m², and 1000 m²) following restoration treatments.  Data were collected prior to treatment application and three growing seasons after thinning and one after burning.

• In this short-term study the thin/burn had more evidence of invasion than the burn-only, thin-only, and control at all scales and abundance measures (richness and cover).
• Six exotic species became significant indicators of the thin/burn when compared to the control after treatment application that were not significant indicators prior to treatment.
• Regression models showed that exotic species richness increased with canopy openness, fire severity, and native richness, and decreased with sapling density.  These findings support a resource limitation model of exotic invasion.