Size asymmetry of resource competition and the structure of plant communities: Commentary on DeMalach et al. 2016
Abstract
The hump-back relationship between diversity and productivity is one of the well-known patterns in ecology that have defied unequivocal explanation (Mittelbach et al. 2001; Sımova, Li & Storch 2013). While it has often been argued that the decline of species richness under high productivity is due to more intense competition, it has never been made fully clear why extinction under high productivity should be more likely compared to low productivity.
DeMalach et al. (2016) present a simple and elegant explanation: it is due to asymmetry in competition for light. Competitive asymmetry means that resources (light in this case) are not divided among competing individuals in proportions corresponding to the size of their resource-acquiring organs, but a bigger individual gets disproportionately more.
It means that the bigger individual gets more also in relative terms, that is per unit biomass.