THE DEVELOPMENT OF ASSOCIATION AND CLIMAX CONCEPTS: THEIR USE IN INTERPRETATION OF THE DECIDUOUS FOREST

Abstract

ECOLOGY is defined as the study of life in relation to environment. It is concerned with what is, and why. The ecological study of single organism frequently meets with almost insurmountable obstacles because environment, if broken down into its component parts, is no longer environment. The ecological study of complex piece of vegetationa forest for example-presents innumerable problems, for the complexity of the environment-with its interacting factors-is multiplied by the complexity of the community; it does not yield to laboratory analysis. The methods of the physiologist fail. Attempts at mathematical interpretation are for the most part static, and they often obscure rather than reveal the true picture of vegetation. Vegetation is dynamic-an ever-changing complex now appearing quiescent and in complete equilibrium -with the habitat, now displaying obvious evidence of change. I believe that failure to recognize the dynamic aspects of vegetation is primary cause of differing concepts. A dynamic approach is es'sential to interpretation of our eastern forests. Observation of natural changes in vegetation long ago resulted in the concept of succession; recognition of quiescent phases led to the climax concept. The association concept arose from the need for designating so-called units of vegetation. Concepts have changed through the years; they should change. As Cooper stated (1926), a periodic inspection of foundations is most desirable. Concepts are bound to change with progress from local or intensive study to broad and extensive study. This is the reason for change with each individual worker; it has in part been the reason for change in concepts through the past 50-60 years of study of vegetation. Geographic location of studies also is factor in the development of concepts. Emphasis of the concepts of association, succession, and climax dates from the work of Henry C. Cowles around the beginning of the century (1899; 1901). Communities were recognized and at first called plant societies, later, plant associations. These were seen to be in equilibrium, more or less, with habitat; however, habitats change through the years, forcing change in vegetation. Changes were recognized as biotic, topographic, and climatic-the biotic due to reactions of the vegetation (and other accompanying life), the topographic to erosional and depositional forces, the