Solidago altissima, a perennial herb of open habitats in eastern North America, is known to exhibit allelopathic properties, which may contribute to its success. To relate chemical variation to ecological function, we grew 24 different clones of Solidago altissima, within single-clone plots. Chemical variation of each clone was quantified via HPLC, with plant chemical composition varying dramatically across the clones, suggesting there may be variation in ecological function. We conducted a greenhouse experiment to link plant chemical composition to interspecific competition. This was done by collecting rhizomes from the Solidago altissima clones and growing them with four target species: Schizachyrium scoparium, Melilotus officinalis, Silphium laciniatum, and Abutilon theophrasti; with five replicates per Solidago altissima clone. ANOVA’s were used to assess variation in the above/below-ground biomass of Solidago altissima clones. Multiple regression analyses were used to relate clone chemical composition to the growth of the four target species.
Results/Conclusions
While rhizome biomass did not vary across clones, above-ground biomass of Solidago altissima varied dramatically. Rhizome and above-ground biomass of each clone were associated with different chemical NMDS axes. Competition from Solidago altissima also varied across target species. Neither Melilotus officinalis or Silphium laciniatum were influenced by any of the NMDS axes of plant chemistry or the above and below-ground biomass of Solidago altissima in the experiment. In contrast, growth of both Schizachyrium scoparium and Abutilon theophrasti were positively influenced by chemical NMDS axis 1, with no direct influence from the above or below ground biomass of Solidago altissima. These findings suggest that the chemistry of Solidago altissima may be a primary driver of competitive outcomes with some species in our system. Allocation of these chemicals also affected Solidago altissima rhizome and above-ground biomass. Chemically-mediated interactions appear to be an important component to the success of Solidago altissima within its native range.