ABSTRACT
Forest invasion in the West generally decreases with increasing elevation (Keeley et al. 2003, Fisher and Fulé 2004), with the greatest threat in lower-lying forests adjacent to invaded grasslands, woodlands, and human developments. Lower-elevation forests are also commonly grazed by livestock and receive greater recreational and off-road vehicle use as well. However, substantial forest areas occupy mid-to high-elevation sites that have been relatively invasion-free. Regardless of elevation, some areas of the Colorado Front
8.1 Introduction .......................................................................................................................... 93 8.2 Exotic species invasive potential following disturbance ............................................... 95 8.3 Exotic plant ecology ........................................................................................................... 102 8.4 Knowledge gaps and research needs .............................................................................. 105 8.5 Synthesis-General relationships, management recommendations,
and conclusions .................................................................................................................. 106 8.5.1 General relationships ............................................................................................ 106 8.5.2 Management recommendations .......................................................................... 106 8.5.3 Conclusions ............................................................................................................. 107
References ..................................................................................................................................... 107
Range, interior Southwest, and Pacific Northwest still exhibit surprisingly little exotic plant invasion (Fornwalt et al. 2003, Laughlin et al. 2004, Anzinger and Radosevich 2008, respectively). As recently as a decade ago, Withers et al. (1999) reported that exotics comprised a lower proportion of total plant species in the mountainous Northwest than in any other region of North America.
