Title: Differential effects of two dominant plant species on community structure and invasibility in an old-field ecosystem
Abstract: In this study, we examined the effects
of Solidago altissima (hereafter Solidago) and two species in
the genus Verbesina, Verbesina virginica and Verbesina
occidentalis (hereafter Verbesina), on the structure of an
old-field plant community and establishment by an invasive plant species,
Lespedeza cuneata (hereafter Lespedeza). We removed
Solidago, Verbesina and both Solidago and
Verbesina from 4-m2 plots in an intact old-field community
during two growing seasons. We then quantified the effects of these removals on
richness, evenness, diversity and composition of the subdominant plant
community. We also measured the total aboveground biomass and the aboveground
biomass of the subdominant community. To assess how these removals affected
establishment by Lespedeza, we planted 20 seeds in each plot and
tracked seedling emergence and survival for one growing season. Subdominant
community evenness and Shannon diversity were higher in plots from which
Solidago and Verbesina were removed relative to control plots.
However, there were no effects of dominant species removal on species richness
or composition of the subdominant community. Total aboveground biomass was not
affected by dominant species removal, suggesting that the community of
subdominant species exhibited compensation. In fact, subdominant community
biomass was greater when Solidago, but not Verbesina, was
removed. Light availability was also greater in plots where Solidago
was removed relative to control plots throughout the growing season. In
addition, removal of dominant species, in particular Solidago,
indirectly reduced the emergence, but not survival, of Lespedeza
seedlings by directly promoting subdominant community biomass. Taken together,
our results suggest that dominant old-field plant species affect subdominant
community structure and indirectly promote establishment by Lespedeza.
[Lara Souza, Jake F. Weltzin & Nathan J. Sanders (2010). Differential
effects of two dominant plant species on community structure and invasibility in
an old-field ecosystem. Journal of Plant Ecology,First published online: November 17.
doi: 10.1093/jpe/rtq027]