PARENT SESSION
Poster Session #4: Invasions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
Fluctuating resources lead to predictable changes in competition and invasibility.
Davis, Mark1, Pelsor, Melissa1, 1
ABSTRACT- The purpose of this three year study was to examine a possible mechanistic relationship between resource availability, competition, and invasibility in an anthropogenic grassland. The experimental design consisted of eight replicates of four treatments--wet weeded, wet unweeded, dry weeded, and dry unweeded. Invasive success of species hand seeded into plots was measured by percent cover and success of transplants by survival. Resource availability (soil water, nitrogen, and light) were also recorded in the plots. We found that both competition and invasibility were strongly affected by resource availability and that fluctuations in resource availability as short as a few weeks had a large impact on invasion success when these fluctuations occurred coincident with the introduction of new propagules. These brief fluctuations in resource availability not only affected initial establishment, they produced measurable, even dramatic, differences in plant survival, growth, and reproduction up to two years following their introduction. Previous hypotheses of invasibility have emphasized the importance of disturbances, species diversity, and community productivity. If resource availability is a primary mechanism controlling invasibility, then it may serve as a unifying concept that can integrate earlier ideas regarding invasibility. The results emphasize the importance that history may play in the invasion process, particularly the occurrence of stochastic, short-lived events that temporarily increase invasibility. This would indicate that it may be very difficult to reconstruct the ecology of particular invasions after the fact.
KEY WORDS: invasibility, invasive species, invasion, competition