. Research methods in ecology. Plant ecology. 278 THE FORMATION different series of zones in the one case, and merely two in the other. 336. Physiographic symmetry. The physical symmetry of a habitat depends upon the distribution of water in it, and this is profoundly affected by the soil and the physiography. The influence of precipitation is slight or lacking, as it is nearly uniform throughout the habitat; the effects of wind and humidity are more localized. Differences of soil rarely obtain within a single habitat, thoiig-h often occurringf in a zoned series. The strikingly.
. Research methods in ecology. Plant ecology. 278 THE FORMATION different series of zones in the one case, and merely two in the other. 336. Physiographic symmetry. The physical symmetry of a habitat depends upon the distribution of water in it, and this is profoundly affected by the soil and the physiography. The influence of precipitation is slight or lacking, as it is nearly uniform throughout the habitat; the effects of wind and humidity are more localized. Differences of soil rarely obtain within a single habitat, thoiig-h often occurringf in a zoned series. The strikingly. Fig. 73. Regional zones on a spur of Pike's Peak (3,800 m.) ; the â forest consists of Picea engelmannii and Pinus aristata, the forewold is Salix pseudolappbnum, and the grassland, alpine meadow (Carex~Cam- panula-coryphium). zonal structure or arrangement of habitats is nearly always due to differ- ences in water-content produced by physiographic factors, slope, exposure, surface, and altitude. The effect of these upon water-content and humidity is obvious. Wherever appreciable physiographic differences occur, there will be central areas of excess and deficiency in water-content, between which there is a symmetrical modification of this factor. Peaks are typical examples of areas of deficiency, lakes and oceans of areas of excess. When these areas are extreme and close to each other, the resulting zonation will be marked; when they are moderate, particularly if they are widely separated,. 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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