A Quantitative Analysis of Wisconsin Forest Vegetation on the Basis of Plant Function and Gross Morphology

Abstract

The structural and functional features of the trees, shrubs, and herbs in the upland forest communities of Wisconsin have been studied for their potential in describing relationships between vegetation and environment. Structure is defined here as the spatial arrangement of the plant biomas, e.g., height, leaf size, and growth form. Functional features include those which are apparent adjustments or response to the environment, e.g., deciduousness, shade tolerance, method of seed dispersal, and fire resistance. Quantitative estimates of the importance of plant features such as these, regardless of species, were obtained for each of 149 forest stands distributed throughout Wisconsin in all types of upland forest vegetation. Using the index of similarity, c = 2w/a + b, each of the 149 stands was compared to every other stand on the basis of 29 tree structural—functional features. The spatial relationships in the resulting ordination demonstrate that the upland forest communities can be distinguished and studied using these features. Although adjacent stands in the ordination are similar on the basis of tree structure and function, they can be different in species composition. The usefulness of grouping species with similar structural—functional features is discussed and related to the concept of ecological equivalence. Finally, the spatial relationships in the ordination are used to derive indices that allow calculation of stand values along structural—functional coordinates. Although the indices are based solely on plant structure, the resulting coordinates can be used to infer some functional features of the vegetation as well as successional status and certain environmental relationships.