TY - JOUR

T1 - Changes in topsoil characteristics with climate and island age in the agricultural zones of the Galapagos

AU - Dinter, Tamara C.

AU - Gerzabek, Martin H.

AU - Puschenreiter, Markus

AU - Strobel, Bjarne W.

AU - Strahlhofer, Matthias

AU - Couenberg, Paulina M.

AU - Zehetner, Franz

PY - 2020

Y1 - 2020

N2 - The flora and fauna of the Galapagos Islands have long been subject to scientific inquiry, but the soils have remained largely ignored until recently. The objective of this study was to assess the differences in main soil characteristics and nutrient reserves within and among the agricultural zones of islands Isabela, Santa Cruz and San Cristobal to provide background information for informed agricultural decision making and a baseline against which future changes may be assessed. Aqua regia-extractable Al and Fe showed a general trend of accumulation with island age and increasing moisture levels within the agricultural zone, while base cations Ca, K, Mg and Na tended to decrease along the same gradients, with some variation likely due to agricultural inputs. Concentrations of silicon, aluminum and iron associated with amorphous constituents (Si-o, Al-o, Fe-o) tended to decrease with island age while iron in crystalline and non-crystalline hydrous oxides (Fe-d) showed a slight increase. Aluminum and iron in non-crystalline and organic complexes were more abundant in areas with higher precipitation. Electrical conductivity, pH in water, pH in sodium fluoride, phosphate retention, organic carbon content and particle size tended to decrease with island age while bulk density increased. Andic properties were expressed in all the soils of the youngest island studied, Isabela, and in higher-elevation soils of the intermediate-age Santa Cruz Island, while the soils of the oldest island studied, San Cristobal, did not show andic properties and were dominated by crystalline clays and iron oxides. The wide range of soil development across the three islands requires soil management recommendations be tailored to each island and even within each island to ensure appropriate stewardship of this important natural resource.

AB - The flora and fauna of the Galapagos Islands have long been subject to scientific inquiry, but the soils have remained largely ignored until recently. The objective of this study was to assess the differences in main soil characteristics and nutrient reserves within and among the agricultural zones of islands Isabela, Santa Cruz and San Cristobal to provide background information for informed agricultural decision making and a baseline against which future changes may be assessed. Aqua regia-extractable Al and Fe showed a general trend of accumulation with island age and increasing moisture levels within the agricultural zone, while base cations Ca, K, Mg and Na tended to decrease along the same gradients, with some variation likely due to agricultural inputs. Concentrations of silicon, aluminum and iron associated with amorphous constituents (Si-o, Al-o, Fe-o) tended to decrease with island age while iron in crystalline and non-crystalline hydrous oxides (Fe-d) showed a slight increase. Aluminum and iron in non-crystalline and organic complexes were more abundant in areas with higher precipitation. Electrical conductivity, pH in water, pH in sodium fluoride, phosphate retention, organic carbon content and particle size tended to decrease with island age while bulk density increased. Andic properties were expressed in all the soils of the youngest island studied, Isabela, and in higher-elevation soils of the intermediate-age Santa Cruz Island, while the soils of the oldest island studied, San Cristobal, did not show andic properties and were dominated by crystalline clays and iron oxides. The wide range of soil development across the three islands requires soil management recommendations be tailored to each island and even within each island to ensure appropriate stewardship of this important natural resource.

KW - Galapagos Islands

KW - Volcanic ash soils

KW - Age sequence

KW - Elevation sequence

KW - Andic properties

KW - Agricultural soils

KW - SANTA-CRUZ ISLAND

KW - SOILS

KW - PEDOGENESIS

KW - THRESHOLDS

KW - EXTRACTION

KW - COMPLEXES

KW - ALUMINUM

KW - GRADIENT

KW - ELEMENTS

KW - BASALT

U2 - 10.1016/j.geoderma.2020.114534

DO - 10.1016/j.geoderma.2020.114534

M3 - Journal article

VL - 376

JO - Geoderma

JF - Geoderma

SN - 0016-7061

M1 - 114534

ER -