Tanacetum bipinnatum germination and competitive interaction with Centaurea stoebe seedlings

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The Michigan Botanist



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Tanacetum bipinnatum (Asteraceae) is threatened in Michigan and endangered in Wisconsin. It is limited in distribution in the Great Lakes region to sand dune ecosystems. Centaurea stoebe (Asteraceae) has invaded many different ecosystems around the Great Lakes region, including dunes. Germination and establishment interruptions for T. bipinnatum may add to the limitations in distribution. I conducted a germination experiment with T. bipinnatum seeds undergoing variable cold storage lengths (0-5 months) and allowed to germinate in the presence and absence of light. Also, I conducted a competition experiment with establishing T. bipinnatum and C. stoebe individuals. With light present for germination, 1 and 2 month cold storage periods had 10% germination. Germination was not independent of cold storage in dark treatments, with only 5% of seeds germinating in controls without cold storage. In competition with C. stoebe, T. bipinnatum had reduced above-ground biomass and root length compared to T. bipinnatum grown with a conspecific and individually. Below-ground biomass for T. bipinnatum was significantly reduced in competition with C. stoebe compared to when it was grown individually. The only alteration in growth for C. stoebe was in below-ground biomass, which was greater in competition with T. bipinnatum. Limited seed germination and competition during establishment may explain why T. bipinnatum occurs at lower densities in areas invaded by C. stoebe. Further research is needed to quantify survival of mature T. bipinnatum beyond the initial establishment in competition with C. stoebe.


invasive, threatened, Lake Huron tansy, spotted knapweed


Biology | Botany

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