. Research methods in ecology. Plant ecology. SUCCESSION 255 the abundance and mobility of certain species enable them to take possession before their proper turn, and to the exclusion of the regular stage. Incom- plete successions are of great significance, inasmuch as they indicate that the stages of a succession are often due more to biological than to physical causes, the proximity arid mobility of the adjacent species being more determinative than the physical factors. Subalpine gravel slides regularly pass through the rosette, mat, turf, thicket, woodland, and forest stages; occasionally
. Research methods in ecology. Plant ecology. SUCCESSION 255 the abundance and mobility of certain species enable them to take possession before their proper turn, and to the exclusion of the regular stage. Incom- plete successions are of great significance, inasmuch as they indicate that the stages of a succession are often due more to biological than to physical causes, the proximity arid mobility of the adjacent species being more determinative than the physical factors. Subalpine gravel slides regularly pass through the rosette, mat, turf, thicket, woodland, and forest stages; occasionally, however, they pass immediately from the rosette, or mat condition, to an aspen thicket which represents the next to the last stage. Such successions are by no means infrequent in hilly and montane regions; in regions phys- iographically more mature or stable, perfect successions are almost invari- ablv the Fig. 35. Half gravel slide formation (Elymus-Muhlenbergia-chal- ichim), stage IV of the talus succession. 314. Stabilization. It may be stated as a general principle that vegetation moves constantly and gradually toward stabilization. Each successive stage modifies the physical factors, and dominates the habitat more and more, in such a way that the latter seems to respond to the formation rather than this to the habitat. The more advanced the succession, i. e., the degree of sta- bilization, the greater the climatic or physiographic change necessary to disturb it, with the result that such disturbances are much more frequent in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Clements, Frederic E. (Frederic Edward), 1874-1945. Lincoln, Neb. , University Pub. Co.
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