Changing methodology results in operational drift in the meaning of leaf area index, necessitating implementation of foliage layer index

Leaf area index (LAI) was developed to describe the number of layers of foliage in a monoculture. Subsequent expansion into measurement by remote‐sensing methods has resulted in misrepresentation of LAI. The new name foliage layer index (FLI) is applied to a more simply estimated version of Goodall's “cover repetition,” that is, the number of layers of foliage a single species has, either within a community or in monoculture. The relationship of FLI with cover is demonstrated in model communities, and some potential relationships between FLI and species’ habit are suggested. FLI (comm) is a new formulation for the number of layers of foliage in a mixed‐species’ community. LAI should now be reserved for remote‐sensing applications in mixed communities, where it is probably a nonlinear measure of the density of light‐absorbing pigments.