Competition and herbivory during salt marsh succession: the importance of forb growth strategy

1 Despite much debate about their importance, only a few field studies have evaluated the intensity of competition and herbivory. 2 Artemisia maritima, Atriplex portulacoides and Plantago maritima, three p lant species which are common in European temperate salt marshes, were tran splanted into different successional stages (15, 30 and 45 years old) of a temperate salt marsh. Biomass of each transplant was measured as the respon se variable to treatments that manipulated competition and the level of her bivory. 3 All species were shown to be negatively influenced by both competition an d herbivory, with competition being in general of greater importance than h erbivory. No change could be detected during succession in the intensity of either competition or herbivory. Their combined impact, however, increased over succession for Atriplex, although no trend was observed for the other two species. 4 Both biomass and allocation patterns reflected further adaptations of the se salt-tolerant species to environmental stress and biotic interactions pr esent in the salt marsh. Plantago, which is the best adapted to salinity, w as shown to be markedly affected by competition and herbivory. Atriplex sho wed less response to herbivory and little response to competition, to which it is well adapted. The grazing-deterrent Artemisia was influenced by herb ivory only as a seedling.