Soil development and mineral transformations along a one?million?year chronosequence on the Galápagos Islands

The Galápagos archipelago is a well-suited model ecosystem for investigating soil evolution. Here, we study mineral transformations and pedogenesis of the volcanic soils in response to weathering duration (1,500–1,070,000 yr) climate (humid vs. dry). Our results show that pH, electrical conductivity, organic C content, cation exchange capacity (CEC), water retention decreased whereas clay content bulk density increased with age under humid climate. Andic properties were expressed ?4,300 yr old, but disappeared relatively early absent ?26,000 old. fraction young andic (?4,300 old) was dominated by allophane ferrihydrite. After 26,000 pedogenesis, illitic–vermiculitic phases predominant, older (?166,000 old), kaolinite, hematite, gibbsite prevailed. sequence orders from youngest second oldest site Histosol–Andisol–Alfisol (vermiculitic)–Alfisol (parasesquic)–Ultisol. chronosequence (1,070,000 met all diagnostic criteria an Oxisol except required low CEC. at two dry comparison sites less developed contents vitric materials (Entisol), dominantly smectitic mineralogy pronounced shrink–swell features 813,000 (Vertisol). highlight rapid transition through Andisol stage during as well strongly divergent pedogenic development zones Islands, both which have important bearings on functioning evolution this unique archipelago.