Competition for light: detection, measurement, and quantification

Abstract

A broad review is presented of (i) indirect and direct methods of detecting and measuring competition for light in plant communities and (ii) simple methods of quantifying light interception by components in a mixture. Competition for light in plant stands may be inferred from the presence of "one-sided" competition, bimodal distributions of plant size, and even (nonrandom) spatial dispersion of plants. However, the outcome depends on the species' response to shadelight. Experimental methods are reviewed for detecting light limitation, distinguishing aboveground and belowground competition, and determining the light "foraging" capacity of plants. Dry matter production by each component in a mixture may be roughly proportional to the amount of light it intercepts. The simple Beer–Lambert equations for light interception are given for monocultures, vertically separated mixtures, and intimate two-component mixtures. These equations emphasize the penalty of being overshadowed. A survey is given of the main methods used to directly measure irradiance and interception in plant canopies.