Twenty—six stands of Wisconsin prairie vegetation, distributed along a moisture gradient, are compared on the basis of plant structure and function. Characters used include method of vegetative propagation, penology, height, life form, leaf size, and root—system structure, and importance in a stand in evaluated from the percentage of the prevalent species with the character. Numerous characters show trends along the moisture gradient, some being more common in the flora of dry parries, others in the flora of wet prairies. Using structural—functional characters, an index is developed to indicate the relative importance of plant characters most common in dry prairie. With this index the stands are arranged according to their relative wetness or dryness. In contrast to compositional indices based on species presence, the structural—functional index has the potential of being applied to similar grasslands around the world, regardless of species differences.

Knight, D. H. (1965). A Gradient Analysis of Wisconsin Prairie Vegatation on the Basis of Plant Structure and Function. Ecology, 46(5), 744–747. Portico.