PARENT SESSION
Poster Session #14: Plant Competition.
Tuesday, August 7, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Application of R* theory to light-limited plant communities may predict relative species abundances in old fields.

BANTA, JOSHUA^1,2, STARK, SCOTT^1,2, STEVENS, M. HENRY^3,2, CARSON, WALTER^1,2, ^{1 2 3}

ABSTRACT- In the northeastern United States, goldenrods often dominate the first two decades of old-fields succession. Solidago altissima, in particular, is widespread, and can reach very high density, typically reducing the abundance of coexisting species. Species may dominate communities by creating equilibrium resource levels (R*) below competing species' tolerances. Solidago altissima may have a lower R* for light than co-occurring species, allowing it to reduce the biomass and flowering of these competing species through shading. We tested the hypothesis that S. altissima dominates early successional plant communities because it has a lower R* (equilibrium resource level) for light than co-occurring species. We compared the light attenuation of four goldenrod species and three aster species. We predicted that S. altissima would have the lowest R* for light, and that overall goldenrod species would have a lower R* than the asters. We found that S. altissima does, in fact, have the greatest ability to attenuate light with increasing density, and that goldenrods did have a greater ability to attenuate light with increasing density than the asters. These differences were not related to plant height. Our results suggest that the R* for light explains patterns of dominance in the early stages of old-field succession in the eastern United States. Specifically, those with the lowest R* for light are the superior competitors and therefore are the dominant species during the early stages of succession.

KEY WORDS: R*, Solidago altissima, goldenrods, asters