Application of the -3/2 Power Law to Clonal Herbs

The -3/2 power law has been useful for describing and understanding density-dependent population regulation in a variety of plant species. It is not clear, however, how the law applies to ramet populations of clonal plants. A graphical model is presented that hypothesizes two possible responses of clonal plant populations to potential density stress. In one situation, the population stabilizes at a density-mean ramet weight combination at which the mean weight is the same as at lower densities. No thinning or density-induced modifications in growth occur. In the second situation, the population continues to increase in density while mean ramet weight declines. There is some evidence that both outcomes are seen in nature. It is also hypothesized that the first outcome should only be observed in clonal plants that occur as pure or discrete clones and in which clonal ramets remain physiologically integrated. Some clonal plants possess these characteristics. Others, for which the second outcome seems to be observed, do not possess these characteristics.