The Structure of Tropical Rain Forest: Synusiae and Stratification

Abstract

A complex plant community is analogous (though admittedly only superficially) to a human society. The members of a human community form social classes, all the members of a given class standing in a similar relationship to the members of other classes and having a similar function in the society as a whole. Each human community thus has a characteristic social structure determined by the nature and the relative importance of the classes which compose it. In a like fashion the species in the more complex plant communities form ecological classes or groups. In the community as a whole the species are of varied stature and varied life-form, but the members of the same ecological group are similar in life-form and in their relation to the environment. These ecological groups, the analogues of the human social classes, will here be called synusiae, a term originally introduced by Gams [1]. A synusia is thus a group of plants of similar life-form, filling the same niche and playing a similar role, in the community of which it forms a part. In the words of Saxton [2], who used the term in a slightly broader sense than Gams, it is an aggregation of species (or individuals) making similar demands on a similar habitat. The species of the same synusia, though often widely different taxonomically, are to a large extent ecologically equivalent.