The Use of Life Form and Growth Form in the Analysis of Community Structure as Illustrated by a Comparison of Two Dune Communities

An introductory discussion traces the development of the concept of community structure, and defines its content. Life form is recognized as the basis upon which community structure is analysed, and the trends in the development of systems of classifying life form are briefly reviewed. The values and limitations of Raunkiaer's system are mentioned and, together with an extended system of classifying growth form, it is adopted for the purpose of comparing community structure in two sand dune systems. This comparison is carried out as an illustration of the relationships between structure and environment discussed in the introduction, and as a contribution to the investigation of the dune habitat and its plant community. Analysis is based solely upon floristic lists with estimates of frequency. The dune communities examined are situated at Luskentyre Banks, Isle of Harris (West Scotland), and at St Cyrus, Kincardineshire (East Scotland). The association between the typical structure of the dune community and the exacting environment is discussed; the importance of vegetative spread and dense growth forms is linked with the mobile substratum, and the high proportions of dwarf growth forms with wind exposure. Under more sheltered conditions taller growth forms may become important. From the general indications of community structure provided by Raunkiaer's system and the additional details from the growth form classification, the influences of climate and of the physical nature of the substratum are regarded as of primary importance. Where these are similar community structure will show a basic similarity, while minor variations will be referable to local variations in climate or substratum.