Crystalline clay constituents of soils from European volcanic systems

Abstract

Soils developed from young volcanic ash are often characterized by the preferential formation of non-crystalline constituents (short-range order minerals) and by the accumulation of organic matter. These non-crystalline materials, together with Al-and Fe-humus complexes, frequently represent a significant part of their colloidal fraction (Shoji and Ono 1978), and determine to a great extent the unique physical and chemical properties and behaviour of Andosols (FAO 2001). Moreover, depending on climate, vegetation cover characteristics, nature of parent material and time of exposure to weathering, a more or less important assemblage of crystalline phases is usually present. The heterogeneity of this mineralogical assemblage is quite large, comprising both 1:1 (hydrated and non-hydrated) and 2:1 layer silicates, as well as Fe-and Al-oxyhydroxides and primary minerals. Though varying in amounts, these materials can play an important role in soil functioning and are also of great importance in understanding soil genesis. © Springer-Verlag Berlin Heidelberg 2007.