From andic non-allophanic to non-andic allophanic Inceptisols on alkaline basalt in Mediterranean climate A toposequence study in the Marghine district (Sardinia, Italy)

摘要

The properties of a non-andic, allophanic Inceptisol (POM1) and two andic, non-allophanic Inceptisols (FLM5 and SPM8), representative of a toposequence on basanite rocks of Mt. St. Antonio (central-western Sardinia, Marghine sub-region), were analyzed to better elucidate factors and processes that lead to a different expression of andic properties and allophane formation in xeric Mediterranean environment. A series of laboratory techniques including physical, chemical, micromorphological, X-ray diffraction (XRD), scanning electron microscopy (SEM) analyses were used. All soils are usually rich in organic carbon, dystric at the Great Group level, with saturation base from 72 to 10%, and with pH from subalcaline to acidic. Allophanic Inceptisol appears more intensely weathered than non-allophanic Inceptisols. Volcanic glass content is, in any case, negligible. POM1, formed on the plateau, shows a shallow solum (45 cm) with A(2) horizon that meets all the criteria for andic soil properties; the amounts acid oxalate-extractable Al-o and Si-o, together with pyrophosphate-extractable Al-p, typifies such a pedon as allophanic Inceptisol (0.19