Does plant competition intensity rather depend on biomass or on species identity?

Weigelt A, Steinlein T, Beyschlag W. Does plant competition intensity rather depend on biomass or on species identity? BASIC AND APPLIED ECOLOGY. 2002;3(1):85-94.In two experiments, we tested whether species specific traits or mainly biomass determines the competitive strength of plant individuals in resource-poor habitats. As measure of competition intensity we calculated the log Response Ratio (lnRR) based on total biomass for three key species of early successional stages on inland dunes. Using seedlings of Corynephorus canescens and Hieracium pilosella in a pot experiment, competition intensity was significantly and positively correlated with the biomass of the respective competitors. In contrast, such a correlation was not detected in a controlled field experiment with adult plants of the two species and of Carex arenaria. However, in both experiments the strength of competitive interactions (measured as lnRR) significantly depended on the identity of the competing species. We conclude, that a biomass advantage over the competitors (which can for instance be achieved by earlier germination) seems to play a crucial role only for successful seedling establishment, while competitive interactions of neighbouring plants depend on species-specific biomass allocation strategies at both developmental stages