Soil origin and duration of a garden experiment affect competitive outcomes between dominant grassland species

QuestionsTo explore whether temporal variation and context dependency of competition may explain alternations in dominance of four dry-grassland species. The species Anthericum ramosum, Brachypodium pinnatum, Bromus erectus, and Inula salicina coexist in one region, each dominating some sites, and have similar habitat affinities and ecological optima. LocationDry grasslands of northern Bohemia, Czech Republic, Europe. MethodsWe assessed interspecific competition at the end of each year of a three-year garden experiment, in all pairwise combinations of species and in a mixture of all species, using multiple competition designs to test for robustness of the observed competitive outcomes. We replicated the experiment in soils from two localities, differing in structure and chemical composition. ResultsBased on a single harvest at the end of the experiment, Brachypodium was the strongest competitor, both in terms of competitive effect and competitive response, and Bromus and Inula the weakest. However, the competition outcomes changed over time: during the first two experimental years, Bromus was the strongest competitor, followed by Inula. Competitive outcomes also depended on soil origin: Bromus was a stronger competitor when grown in soil resembling soil at the sites it naturally dominates while Inula showed the opposite pattern. ConclusionsWe showed that variation in competitive abilities of individual species over time, under different competition scenarios and in soils of different origin provide the opportunities for each species to locally dominate over the others.