Ecological differentiation of Carex species coexisting in a wet meadow: Comparison of pot and field experiments

Abstract

Competitive exclusion is to be expected between phylogenetically similar species that share traits and resources. However, species may overcome this, either through differentiation of their responses to biotic and abiotic conditions, or by trait differentiation, thus enabling their coexistence. We identified differences in phenotypic traits between seven coexisting Carex species and their responses to competition and fertilization in pot experiments, before using long-term field experiments to generate responses of the Carex species to fertilization and mowing and to illustrate temporal variability between species. Finally, we assessed how effective the results of the pot experiment were at predicting species responses in the field. In pot experiments, we found that species responded more to competition than to fertilization. Notably, all species showed similar responses to these factors in the pot experiments. Fertilization decreased the root:shoot ratio, whilst competition decreased growth-related characteristics such as total biomass, irrespective of the species. Differences among species were only found in their clonal response to competition, namely rhizome production and generation rate of new ramets. These findings support the idea that different clonal growth strategies may facilitate niche partitioning of Carex species. Species responses measured from pot experiments were poor predictors of their responses in the field experiment. Nevertheless, we confirmed the prediction that, over time, Carex species with lower growth rates in pot experiments showed more stable biomass production than in the field. We suggest that differences in clonal traits and temporal dynamics support the ability of Carex species to avoid competitive exclusion, enabling their coexistence.