PARENT SESSION
Poster Session 20: Invasive Species
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Evaluating dominance as a component of non-native species invasions.
Newman, Gregory1, Crall, Alycia*,1, Stohlgren, Thomas2, Evangelista, Paul1, Guenther, Debra1, 1 Colorado State University, Fort Collins, CO2 USGS, Fort Collins, CO
ABSTRACT- How are non-native species invasion patterns affected by including dominance as a component of invasion? What factors best predict non-native species dominance in an arid ecosystem? Can areas susceptible to high dominance be distinguished from areas of low dominance? To explore these questions, we re-examined a 6-year dataset of 323 0.1 ha plots collected in the Grand Staircase-Escalante National Monument from 1998 to 2003, specifically focusing on Bromus tectorum (a notable dominant non-native annual within this system). We found that non-native species establishment and dominance are both occurring in species-rich, mesic vegetation types. Therefore, non-native species dominance may result despite many equally abundant native species rather than a dominant few, and competitive exclusion does not seem to be a primary control on the invasion patterns seen here. Although we found a significant decrease in non-native dominance with increasing native species richness, this decrease was only slight and little variation in non-native dominance could be explained by native species richness (p = 0.02; R2 = 0.01). However, regression tree analysis that included additional biotic and abiotic variables was no better at predicting non-native species dominance (PRE=0.49) and B. tectorum dominance (PRE=0.39) than at predicting establishment. Land mangers will need to set priorities for control efforts on the more productive, species-rich vegetation types that appear to be susceptible to both components of invasion.
Key words: non-native species, dominance, Bromus tectorum, Grand Staircase-Escalante National Monument