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In order to test whether predictions of mortality and size hierarchy development, as derived from studies of non-clonal plants, are valid for clonal plants, an experiment was carried out with Brachypodium pinnatum and Carex flacca, two rhizomatous herbs, planted at three densities. Competition was studied at two levels of organization, the shoot (ramet) and the clone (the individual plant consisting of all interconnected ramets). Size inequalities (measured as Gini coefficients), size-dependent growth and mortality of both shoots and clones were analysed over a period of two years. The species were grown in monocultures in three treatments that differed in clone density. At the end of both the first and the second year of the experiment there were not significant differences in Gini coefficients of shoot height or weight between treatments (...)

The results of previous workers suggest that rhizome lengths and the degree of rhizome branching in clonal perennial plants may change in response to environmental conditions, enabling plants to more efficiently capture unevenly distributed resources (so-called "foraging" responses). Such components of plant growth were investigated in two rhizomatous graminoids of chalk grassland, Carex flacca and Brachypodium pinnatum. Mean rhizome length in Brachypodium was significantly smaller under high nutrient availability, but only when unshaded. Carex produced longer rhizomes under high light conditions, but showed no effects of nutrients. In both species, branching was greater under higher levels of light intensity, and with more favourable nutrient conditions. Shoots of both species increased in height in response to shading, but only shoots of Brachypodium responded to fertilization. As Carex does not produce shorter rhizomes under more favourable conditions, the foraging model is inapplicable to this species. Growth responses of Brachypodium were in better agreement with the foraging hypothesis. However, in this species the amount of endogenous variation in rhizome length and bud dynamics overrides the plastic changes in response to different resource supply.