Research methods in ecology

by Frederic E. Clements

PRESENT STATUS OF ECOLOGY

10. The lack of special training. The bane of the recent development popularly known as ecology has been a widespread feeling that anyone can do ecological work, regardless of preparation. There is nothing in modern botany more erroneous than this feeling. The whole task of ecology is to find out what the living plant and the living formation are doing and have done in response to definite complexes of factors, i. e., habitats. In this sense, ecology is practically coextensive with botany, and the student of a local flora who knows a few hundred species is no more competent to do ecological work than he is to reconstruct the phylogeny of the vegetable kingdom, or to explain the transmission of ancestral qualities. The comprehensive and fundamental character of the subject makes a broad special training even more requisite than in more restricted lines of botanical inquiry. The ecologist must first of all be a botanist, not a mere cataloguer of plants, and he must also possess a particular training in the special methods of ecological research. He must be familiar with the various points of attack in this field, and he must know the history of his subject thoroughly. Ecology affords the most striking example of the prevalent evil of American botanical study, i. e., an indifference to, or an ignorance of the literature of the subject. The trouble is much aggravated here, however, by the breadth of the field, and the common assumption that a special training is unnecessary, if not, indeed, superfluous. Ignorance of the important ecological literature has been a most fertile source of crude and superficial studies, a condition that will become more apparent as these fields are worked again by carefully trained investigators.

11. Descriptive ecology. The stage of development of the subject at the present time may be designated as descriptive ecology, for purposes of discussion merely. This is concerned with the superficial description of vegetation in general terms, and results from the fact that the development has begun on the surface, and has scarcely penetrated beneath it. The organic connection between ecology and floristic has produced an erroneous impression as to the relative value of the two. Floristic has required little knowledge, and less preparation: it lends itself with insidious ease to chance journeys or to vacation trips, the fruits of which are found in vague descriptive articles, and in the multiplication of fictitious formations. While there is good reason that a record should be left of any serious reconnaissance, even though it be of a few weeks’ duration, the resulting lists and descriptive articles can have only the most rudimentary value, and it is absurd to regard them as ecological contributions at all. No statement admits of stronger emphasis, and there is none that should be taken more closely to heart by botanists who have supposed that they were doing ecological work. An almost equally fertile source of valueless work is the independent treatment of a restricted local area. The great readiness with which floristic lists and descriptions can be made has led many a botanist, working in a small area, or passing hurriedly through an extended region, to try his hand at formation making. From this practice have resulted scores of so-called formations, which are mere patches, consocies, or stages in development, or which have, indeed, no existence other than in the minds of their discoverers. The misleading definiteness which a photograph seems to give a bit of vegetation has been responsible for a surplus of photographic formations, which have no counterparts in nature. Indispensable as the photograph is to any systematic record of vegetation, its use up to the present time has but too often served to bring it into disrepute. There has been a marked tendency to apply the current methods of descriptive botany to vegetation, and to regard every slightly different piece of the floral covering as a formation. No method can yield results further from the truth. It is evident that the recognition and limitation of formations should be left absolutely to the broadly trained specialist, who has a thorough preparation by virtue of having acquainted himself carefully with the development and structure of typical formations over large areas.

12. The value of floristic. In what has been said above, there is no intent to decry the value of floristic. The skilled workman can spare the material which he is fashioning as readily as the ecologist can work without an accurate knowledge of the genera and species which make up a particular vegetation. Some botanists whose knowledge of ecology is that of the study or the laboratory have maintained that it is possible to investigate vegetation without knowing the plants which compose it. Ecology is to be wrought out in the field, however, and the field ecologist—none other, indeed, should bear the name—understands that floristic alone can furnish the crude material which takes form under his hands. It is the absolute need of a thorough acquaintance with the flora of a region which makes it impossible for a traveler to obtain anything of real ecological value in his first journey through a country. As the very first step, he must gain at least a fair knowledge of the floristic, which will alone take the major part of one or more growing seasons. This information the student of a local flora already has at the tip of his tongue; in itself it can not constitute a contribution to ecology, but merely the basis for one. In this connection, moreover, it can not be used independently, but becomes of value only after an acquaintance with a wide field. Floristic study and floristic lists, then, are indispensable, but to be of real value their proper function must be clearly recognized. They do not constitute ecology.

13. Reconnaissance and investigation. In striving to indicate the true value and worth of ecological study, it becomes necessary to draw a definite line between what we may term reconnaissance and investigation. By the former is understood the preliminary survey of a region, extending over one or two years. The objects of such a survey are to obtain a comprehensive general knowledge of the topography and vegetation of the region, and of its relation to the other regions about it. The chief purpose, however, is to gain a good working acquaintance with the flora: a reconnaissance to be of value must do this at all events. Certain general facts will inevitably appear during this process, but they will invariably need the confirmation of future study. It would be an advantage to real ecology if reconnaissance were to confine itself entirely to the matter of making a careful floristic survey. Investigation begins when the inquiry is directed to the habitat, or to the development and structure of the formation which it bears, i. e., when it takes up the manifold problems of the οἶκος. Such a study must be based upon floristic, but the latter becomes a part of investigation only in so far as it leads to it. Standing by itself, it is not ecological research: it is the preparation for it. This distinction deserves careful thought. The numerous recruits to ecology have turned their attention to what lay nearest to hand, with little question as to its value, or to where it might lead. The result has been to make reconnaissance far outweigh investigation in amount, and to give it a value which properly belongs to the latter. Furthermore, this mistaken conception has in many cases, without doubt, prevented its leading to valuable research work.

14. Resident investigation. Obviously, if reconnaissance is a superficial survey, and investigation thorough extensive study, an important distinction between them is in the time required. While one may well be the result of a journey of some duration, the other is essentially dependent upon residence. In the past the great disparity between the size of the field and the number of workers has made resident study too often an ideal, but in the future it will be increasingly the case that a particular region will be worked by a trained ecologist resident in it. This may never be altogether true of inaccessible and sterile portions of the globe. It may be pointed out, however, that, between the tropics and the poles, residence during the summer or growing period is in essence continuous residence. In the ultimate analysis, winter conditions have of course some influence upon the development of vegetation during the summer, but the important problems which a vegetation presents must be worked out during the period of development. For temperate, arctic, and alpine regions, then, repeated study during the growing period for a term of years has practically all the advantages of continuous residence. For all practical purposes, it is resident study.

15. The dangers of a restricted field. In the resident study of a particular region, the temptation to make an intensive investigation of a circumscribed area is very strong. The limits imposed by distance are alone a sufficient explanation of this, but it is greatly increased by the inclination toward detailed study for which a small field offers opportunity. This temptation can be overcome only by a general preliminary study of the larger region in which the particular field is located. The broader outlook gained in this way will throw needed light upon many obscure facts of the latter, and at the same time it will act as a necessary corrective of the tendency to consider the problems of the local field in a detached manner, and to magnify the value of the distinctions made and the results obtained. Such a general survey has the purpose and value of a reconnaissance, and is always the first step in the accurate and detailed investigation of the local area or formation. Each corrects the extreme tendency of the other, and thorough comprehensive work can be done only by combining the two methods. When the field of inquiry is a large area or covers a whole region, the procedure should be essentially the same. A third stage must be added, however, in which a more careful survey is made of the entire field in the light of the thorough study of the local area. The writer’s methods in the investigation of the Colorado vegetation illustrate this procedure. The summers of 1896, 1897, 1898 were devoted to reconnaissance; those of 1899–1904 were given to detailed and comprehensive study by instrument and quadrat of a highly diversified, representative area less than 20 miles square, while the work of the final summer will be the application of the results obtained in this localized area to the region traversed from 1896–98. This is practically the application of methods of precision to an area of more than 100,000 square miles. It also serves to call attention to another point not properly appreciated as yet by those who would do ecological work. This is the need of taking up field problems as a result of serious forethought, and not as a matter of accident or mere propinquity. A carefully matured plan of attack which contemplates an expenditure of time and energy for a number of years will yield results of value, no matter how much attention an area may have received. On the other hand, an aimless or hurried excursion into the least known or richest of regions will lead to nothing but a waste of time, especially upon the part of the ecologist, who must read the articles which result, if only for the purpose of making sure that there is nothing in them.