ABSTRACT
Two key figures in the early development of plant ecology were H. C. Cowles and F. E. Clements. Their studies in North America led to a set of principles which had a profound influence on many ecologists in the first half of the twentieth century. Both were interested in how the species composition of vegetation changed over time. In 1899 Cowles published his studies of sand-dune vegetation around Lake Michigan, tracing the changes as a few early established plants were joined by or replaced by other species to form more complex communities. His results influenced, in particular, Clements who presented over the next few decades theories held to be generally applicable to these types of vegetation development wherever they occurred. More recently much of this work has been heavily criticized, but a review of Clements’ theories forms a suitable starting point for an understanding of current views on the nature of vegetation.
