Biological Soil Crusts of Asia Including the Don and Volga Region
Information on biological soil crusts in Asia is extremely rare and scattered throughout the literature. Language barriers make it difficult to identify relevant publications. Although scientific literature on soil algal and cyanobacterial communities fro
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7.1 Introduction Information on biological soil crusts in Asia is extremely rare and scattered throughout the literature. Language barriers make it difficult to identify relevant publications. Although scientific literature on soil algal and cyanobacterial communities from the former USSR is fairly abundant (e.g., Bolyshev and Manucharova 1947; Gollerbakh et al. 1956; Forest 1965; NovichkovaIvanova 1980), reports on soil cyanobacteria, algae, and lichens from other countries are usually restricted to single publications chronicling expeditions to specific biomes or regions (e.g., Cogt 1979; Huneck et al. 1984, 1987, 1992). In addition, most studies focused on the soil independent of its relationship to biological soil crusts (see Novichkova-Ivanova 1980). As a result, information on crust-forming organisms is scattered and is found partly in the phycological and lichenological literature that addresses “subaerial” algae (including cyanobacteria) and/or terricolous lichens. Because of their close phytogeographical relations to Asia, biological soil crusts of the eastern European Volga and Don region are included in this chapter as well.
7.2 Semideserts and Deserts of the Lower Courses of the Volga and Ural River The semidesert region along the lower courses of the Volga and the Ural Rivers extends eastward to the foothills of the Altai. Within this region, crusts composed of cyanobacteria, lichens, and more rarely mosses and liverworts, cover large areas (Keller 1930). The crusts are more abundant in the northern parts of the semidesert. However, these crusts do not form compact, luxurious carpets, but rather scattered black patches when dry. After rainfall, they become greenish and prominent. The soils on which the crusts occur belong to the bright chestnut or brown-colored solonetz type. According to the Ecological Studies, Vol. 150 J. Belnap and O.L. Lange (eds.) Biological Soil Crusts: Structure, Function, and Management © Springer-Verlag Berlin Heidelberg 2001
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author, the main activity time of the crusts is spring and autumn. During summer, activity depends on rainfall events. The most prominent cyanobacterium in these soil crusts is Microcoleus vaginatus (Vauch.) Gom. Occurring less frequently are Scytonema ocellatum Lyngbye ex Bornet et Flahault and scattered thalli of Nostoc commune (L.) Vaucher ex Bornet et Flahault. Nostoc flagelliforme Berk. et Curtis, with its characteristic large, hair-like thalli, occurs in some parts of the region (Keller 1930). However, both Nostoc species mentioned contribute to crust formation only during certain stages of their life cycles. Their large, easily visible thalli do not penetrate and are not fixed to the upper soil surface, and are thus not an integral part of the crust. Only their hormogonia and thallus primordia have an endedaphic phase. In the semideserts of the lower Volga and Ural rivers, 44 different soil lichen taxa have been reported (Keller 1930). Only a few of them are found in soil crusts, including Diploschistes scruposus var. terrestris Per
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