Andisols of Turkey: An example from the Cappadocian Volcanic Province

Abstract

A number of studies have been conducted on the genesis of soils from volcanic deposits in semi- humid and humid climates. However, there has been little study of the mineralogical properties and genesis of soils from volcanic rocks in arid and semi-arid climates. This study was conducted to understand the genesis of soils from different volcanic parent materials, such as andesite, dacite, volcanic ash, basalt and ignimbrite, in the region east of the Erciyes stratovolcano in Central Anatolia. At least three soil profiles were selected from each parent material, and 17 soil profiles were described. Soil samples were also taken from each soil horizon for physical, chemical and mineralogical analyses. Soil profiles vary according to elevation and the types of derived-parent materials and are divided into 17 pedons and 15 horizons (2A, 2Bw, 2Bw1, 2C, A2, BC, Bw, Bw1, Bw2, Bw3, C, C1, C2, Cr, R). Soil acidity varied from slightly alkaline to slightly acidic in all soils. Organic matter contents were higher in the surface horizons and generally decreased with depth in all pedons. The extractable cation values of ammonium oxalate, pyrophosphate, dithionite-citrate and sodium pyrophosphate, as well as unhydrolyzed volcanic glass, allophone, imogolite, smectite and ferrihydrite contents of the soils, are variable based on the parent materials, pedons and elevations that are typical of the Cappadocian volcanogenic soils in Anatolia of Turkey. These soils can generally be described as alu-andic Andisols, due to their Alo+1/2Feo values and Alp/Alo ratios. The important factors affecting the formation and development of soils are climatic variations affecting horizon development and genesis, soil parent material diversities and leaching regimes originating from elevation differences.