Zonobiome of the Arid-Temperate Climate

Abstract

In Eurasia, this continental zonobiome stretches from the mouth of the Danube across eastern Europe and Asia, almost to the Yellow Sea. In North America, it occupies the entire Midwest, from southern Canada to the Gulf of Mexico. The degree of aridity varies considerably, and four subzonobiomes can be distinguished: (1) a semiarid subzonobiome having a short period of drought, with steppe and prairie vegetation (Fig. 87, Chkalov); (2) a very arid subzonobiome with a type VII climate (rIII), i.e., with as little rain (falling in winter) as the subtropical desert climate; (3) a subzonobiome similar to 2, but with summer rain; and (4) deserts of the cold mountainous plateaus (Tibet and Pamir). Thus Subzonobiomes 2 and 3 are genuine deserts, although the winters are cold. For practical purposes, it is helpful to distinguish an arid semidesert ecotone with a type VIIa climate between Subzonobiomes 1 and 2 and 1 and 3 (Fig. 87, Astrakhan). The semideserts (the sagebrush region in North America) are also more arid than the steppes but less arid than the deserts, and the vegetation is of a transitional type, although there is a well-developed drought lasting about 4–6 months.