Zonation

zonation [zō′nā·shən]

(ecology)

Arrangement of organisms in biogeographic zones.

(geology)

The condition of being arranged in zones.

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Zonation 

(geographic), the pattern of differentiation of the geographic sphere (landscape) of the earth, manifest in the sequential and definite change of geographic belts and zones and resulting primarily from differences in the amount of solar energy reaching particular latitudes on the earth’s surface.

Zonation is also characteristic of most of the components and processes of the natural geographic regions—climatic, hydrological, geochemical, and geomorphological processes; the soil, plant cover, and animal life; and to some extent the formation of sedimentary rocks. A decrease in the angle of the sun’s rays as they strike the earth from the equator to the poles creates broad latitudinal belts of radiation: a tropical zone, two temperate zones, and two cold zones. The formation of analogous belts, especially climatic and geographic belts, is related to the characteristics of the atmosphere and atmospheric circulation, and these are strongly influenced by the distribution of land and oceans, which is not zonal. The differentiation of natural zones on land depends on the pro-portion of heat and moisture, which changes not only with latitude but also from the coastal area to the continental interior (patterns of sectionalization). Thus it is possible to speak of horizontal zonation, which is particularly well shown by the latitudinal zonation on the plains of the USSR. Each geographic belt and sector has its spectrum and sequential order. Zonation is also expressed in the regular progression of altitudinal zones, or belts, in mountains, which is originally determined by a nonzonal factor, the relief; moreover, definite spectra of altitudinal zones are characteristic of particular belts and sectors. Both horizontal and vertical zonation are expressed in oceans (by consecutive changes in temperature, salinity, biocomponents), over which geographic belts extend.

Zonation of thermal conditions was recognized as early as classical times. Climatic and plant zonation, including altitudinal zonation, was established by the German scientist A. von Humboldt. Zonation was first defined as a fundamental law of differentiation of major natural complexes by V. V. Dokuchaev in 1898.

E. N. LUKASHOVA