Allelopathic Effects of Goldenrod Species on Turnover in Successional Communities

—While goldenrod species are often found to be allelopathic in laboratory settings, its importance in controlling plant community dynamics has been much more difficult to assess. We designed a study to determine whether allelopathy is related to the success of goldenrods in abandoned agricultural land. To accomplish this, we conducted laboratory bioassays for six co-occurring goldenrod species and compared these results to the cover and impacts of these species in the field. We determined the germination responses of two target species to a gradient of leaf extract concentrations to assess the allelopathic potential of these goldenrods. We also used long-term successional data to determine the influence of each goldenrod species on community turnover. Germination percentages in the lab were reduced by leaf extracts for most goldenrod species and varied dramatically among species. In the field, influences of goldenrods on their associated communities were weak and opposite expected allelopathic effects, as the number of associated species generally increased with goldenrod cover. The relative strength of allelopathy among goldenrods was not related to the abundance achieved during succession. In this system, we documented the potential for goldenrods to exhibit allelopathic interactions in a controlled situation. However, these effects were not strong enough to alter community structure and turnover.