The Use of Phytosociological Methods in Ecological Investigations: II. Practical Issues Involved in an Attempt to Apply the Braun-Blanquet System

The main conclusions of this discussion can be summarized as follows: 1. Absolute uniformity in vegetation or habitat does not exist, but it is possible to find various levels of relative uniformity, any of which may be selected according to the degree of exactitude required for particular research problems. One such level of uniformity has been chosen to exemplify the use of plant sociological techniques in a study of the vegetation of the Breadalbane district of Perthshire. (The field study and conclusions derived from it will appear in succeeding parts.) 2. By the description of numerous stands of `uniform' vegetation, abstract points of reference (called noda above), can be established which coincide with frequently occurring and easily recognizable plant communities. 3. These points can be defined most exactly and most readily by the constant and the dominant species together. Neither the faithful species nor the dominant alone are suitable. 4. Not all the vegetation of a region can be attributed to these described noda; many communities may be intermediate; but the noda should be sufficiently numerous that all the vegetation can be described in terms of them. The combination of the methods of various schools which I have adopted results from an attempt to rationalize and examine critically the technique of the Braun-Blanquet school. The application of this revised version to a field problem leads inevitably to a conception of the problems of vegetational classification, which diverges from Braun-Blanquet's. This will emerge in subsequent articles.