PARENT SESSION
Oral Session #20: Invasions: Effects of invaders -- terrestrial systems. Presiding: R. Callaway.
Tuesday, August 7, 2001. 8:00 AM to 12:00 PM. Madison Ballroom C.
Species richness and patterns of invasion over 40 years of old field succession.
Meiners, Scott1, Cadenasso, Mary2, Pickett, Steward2, 1 2
ABSTRACT- The relationship between diversity and community invasibility has been studied in detail for a few plant species, largely in short-term experiments. Evaluation of long-term patterns of invasion is needed to fully assess this relationship. We used 40 years of continuous permanent plot data from the Buell-Small succession study to examine the relationship between diversity and invasion for 14 native and 12 exotic species. Species included in the analysis occurred across the entire 40-year span of the study and included annuals, biennials, woody and herbaceous perennials, and lianas. Using logistic regression, we related the species richness of plots to the likelihood that a plot later became invaded by a particular species. Species varied in their response to initial plot richness. Ten species showed no statistically significant relationship between initial plot richness and the probability of invasion. An increase in the likelihood of invasion with increasing richness was found in ten species and while a decrease in the likelihood of invasion was only found in one species. Significant hump-shaped relationships, where invasion was highest at intermediate levels of richness, were found for five species. These varied responses were unrelated to a species' nativity, life form or seral stage. This study illustrates the need for more research to determine the breadth of diversity responses within plant communities.
KEY WORDS: Invasions, Diversity, Succession, Invasibility