Competition and Succession on a Rocky Mountain Fellfield

Abstract

During work in Alaska, in the northern Rocky Mountains, and in the mountains of northeastern America which led to conclusions and publications on timberlines (Griggs 1934a, 1938, 1946) the ecology of the tundra beyond the tree limit was always in the background of my study and thinking. Throughout this work I devoted more time and effort to studying the arctic-alpine vegetation beyond the trees than to timberline itself. But I was unable to resolve to my own satisfaction the problem of the tundra. (Griggs 1934b, 1936.) I am not the only one who has been baffled in his effort to understand arctic-alpine Weaver and Clements (1938) say, tundra climax consists chiefly of four communities, the successional relations of which are little understood as yet. That is to say: The many seasons that Clements spent at his Alpine Laboratory in Colorado did not bring to him a satisfactory understanding of the tundra. In his great work on the Botany of the Canadian Eastern Arctic (Polunin 1948: 3) remarks, concerning the analogous situation in the Arctic Archipelago: more I learned about the vegetation as a whole, the less I felt inclined to generalize about it for if one impression stands out from among all my studies of the vegetation of the Canadian Eastern Arctic, it is that of extreme (and often to me inexplicable) variability from place to place. Certainly there will long remain a great deal more to discover: nor is our knowledge as yet nearly sufficient to allow of detailed comparison with other arctic or subarctic lands. Whitehead (1951: 349) begins his discussion with the observation, Relatively little ecological work appears to have been done on mountain summit regions, other than descriptions of vegetation. It is clear enough that the methods of conventional ecology as it has developed in the temperate zone have not led to a satisfactory solution of the problem of arctic-alpine I am therefore trying a new approach which can, I believe, lead us into a sound understanding of arcticalpine ecology. Much of the trouble arises, so it seems to me, from premature attempts to deal with arcticalpine regions from the point of view of syn1 Collaborator, U. S. National Park Service. ecology. Autecology offers a simpler, less complicated approach. Study has convinced me that only when we understand the ecology of individual arctic or alpine species can we synthesize an understanding of arctic-alpine I am therefore studying the tundra, species by species. The approach used resembles somewhat that adopted by Oosting and his associates (Keever, Boosting, and Anderson 1951) in studying succession on exposed granite rocks. My studies were made during the open seasons of 1952, 1953, 1954, and 1955. For the present, however, I am concentrating my attention on fellfields and habitats transitional from fellfields where the plants stand apart from each other. The reason for this decision will be evident to anyone who examines a small area, say a square foot, of closed or partly closed tundra. He observes several to many species growing together. Doubtless an intense struggle for survival is going on among those plants but it is extremely difficult to find means of assessing the relative potencies in the struggle of the species present. But on the bare gravel of the fellfield each individual plant has its own struggle for existence uncomplicated with others. That is, it is uncomplicated unless other plants happen to invade the area. Then the struggle is a relatively simple duel whose progress may be watched with comparative ease over the years even though we have as yet little inkling as to the character of the weapons each species brings to the contest. The present study is an attempt to elucidate the stages in this struggle on a particular fellfield. It is hoped that this study may invite comparisons with other fellfields and so set the stage for comparative ecology of arctic-alpine regions. Also it is hoped that study of the fellfield may lead to an understanding of the higher stages in the succession.