Restoration ecology of an endangered plant species:: Establishment of new populations of Cirsium pitcheri

We determined the effects of shade, burial by sand, simulated herbivory, and fertilizers on the survival and growth of artificially planted population of Cirsium pitcheri-an endangered plant species of the sand dunes along Lake Huron. Sand burial experiments showed that greenhouse grown plants should optimally be transplanted into areas receiving 5 cm of sand deposition: burial at this depth maximized emergence, survivorship, and below-ground biomass. Under field conditions, simulated herbivory of up to 50% of the plant height produced a slight increase in biomass after one year of growth. Field observations showed that when white-tailed deer removed more than 50% of the transplant's leaf tissue, the plant died. The application of a 20:20:20 (N:P:K) water-soluble fertilizer produced a significant increase in the dry leaf biomass, total leaf area, and total dry biomass relative to control plants. We also tested for the presence or absence of a persistent seed bank. Few seeds were recovered from soil samples collected from Finery Provincial Park and Providence Bay. However, C. pitcheri has the ability to form a persistent seed bank under field conditions but only at soil depths of greater than or equal to 15 cm. Cirsium pitcheri seeds are able to germinate and seedlings can emerge from a burial depth of up to 6 cm. Thus, seeds planted in open, sunny areas will probably maximize emergence, growth, and survivorship of seedlings. Populations of C. pitcheri can be restored by planting seeds at shallow depths, transplanting greenhouse-grown plants, applying water soluble fertilizers, and protecting plants from herbivores.