The impact of herbivory and competition on flowering and survival during saltmarsh succession

For succession, the establishment and turnover of plants, in terms of gener ative spreading and renewal, is of crucial importance. Especially the succe ss of seedling establishment into the existing vegetation might be of prime importance for the further development of plant species composition. Flowe ring, on the other hand, is the necessary first step towards generative out put and later seed set. In a chronosequential gradient of a saltmarsh succe ssion, we investigated the performance of transplants of three common speci es under different conditions: Artemisia maritime, Atriplex portulacoides a nd Plantago maritime were transplanted as seedlings and mature plants into plots in early-, mid-, and late-successional stages (15, 30 and 40 years) o n the Dutch island of Schiermonnikoog. Natural herbivory (by hares and gees e) and neighbourhood competition were excluded in a factorial design. Flowe ring and survival rates of the three species were generally greatly reduced under natural conditions, compared to competition- and herbivory-free plot s. The survival rates of Artemisia maritima and Plantago maritima reflect t heir position as early-successional species: early in succession, both show their highest survival and abundance. For late-dominant Atriplex portulaco ides a different explanation has to be invoked for the medium-high survival and low abundance: probably winter grazing by hares and the importance of a high nitrogen supply rate, rather than flowering and survival, determine its low abundance in the early and mid-phase of this saltmarsh succession. Some long-term impacts of herbivores affecting flowering and survival are d iscussed.