Effects of land-use change on morphological, physicochemical, and mineralogical properties of volcanic soils in southern Chile

Chilean volcanic soils, such as Andisols and Ultisols, cover much of the country’s arable land and are valued for their unique mineralogical characteristics. This study investigated the effects of land-use change from native forest to silvoagricultural systems on pedogenesis across four volcanic soil types: Acrudoxic Duraquand, Duric Hapludand, Typic Paleudult, and Typic Hapludult. Morphological analyses revealed that soils under agricultural uses have undergone changes in soil structure in addition to a loss in organic horizons. Significant differences were noted in physical and chemical properties, including bulk density, soil organic carbon (SOC), pH, and extractable aluminum. Andisols under croplands displayed higher bulk densities, lower SOC, and decreased extractable aluminum contents compared to those under native forests. Principal component analyses (PCA) revealed a distinct separation between land uses based on andic properties, suggesting, in some cases, a partial loss of these distinctive characteristics. Mineralogical analyses detected allophane, gibbsite, kaolinite, and hydroxy-interlayered minerals; however, no direct evidence was found for crystalline clay mineralogical transformations due to land-use change. Furthermore, while future studies would benefit from a finer-scale soil classification to account for the geomorphological variability of southern Chile, the present findings already highlight clear impacts of land-use change on pedogenesis in volcanic soils. Keywords: Volcanic soils, Land-use change, Pedogenesis, Andic properties, Soil mineralogy.