EFECTO DEL CAMBIO DE USO EN LA ESTABILIDAD DE LA ESTRUCTURA Y LA FUNCIÓN DE LOS POROS DE UN ANDISOL (TYPIC HAPLUDAND) DEL SUR DE CHILE

Volcanic soils in southern Chile cover approximately 60% of the arable land in the country. These soils are under a wide range of land uses from pristine systems to intensively used ones. The objective of this study was to determine the effect of the land use change on: i) the structural stability after external and internal forces, ii) the hydraulic conductivity and iii) its functional resilience. Disturbed and undisturbed soil samples were collected at 5, 20 and 40 cm depths in an Andisol (Typic Hapludand) under native forest (NF), 50 year old pasture (P50) and 1 year old pasture (PI). The water retention, shrinkage and consolidation curves, hydraulic conductivity (Ks), air permeability (Ka), organic carbon content (CO), soil texture and allophane contents were determined. The unsaturated hydraulic conductivity (Ku) was estimated according to van Genuchten (1980). Soil deformation indexes as a consequence of mechanical (COLEm) and hydraulic (COLEh) stresses were calculated. The studied soil is subject to continuous changes in their structure as a consequence of mechanical and hydraulic stresses affecting the pore size distribution and its functionality. The magnitude of these changes decreased with the increasing intensity of the land use. The great shrinkage capacity of the soil may have consequences on its hydraulic behaviour depending on the drying intensity through the formation of cracks and preferential path flows. Finally, the soil pores are able to recover its functional integrity after compaction, which is strongly related to the presence of organic matter contents. Los suelos volcánicos del sur de Chile constituyen cerca del 60% del suelo arable del país. Estos suelos se encuentran bajo un amplio rango de usos desde sistemas prístinos hasta otros con un uso intensivo. El objetivo de este trabajo fue determinar el efecto del cambio de uso de suelo sobre: i) la estabilidad del suelo frente a presiones externas e internas; ii) la conductividad hidráulica y iii) su resiliencia funcional. Muestras disturbadas y no disturbadas de suelo fueron recolectadas a 5, 20, 40 cm de profundidad en un suelo Andisol (Typic Hapludand) bajo un renoval de bosque nativo (NF), una pradera de 50 años (P50) y otra de 1 año de uso (Pl). Se determinó la curva de retención de agua, contracción y consolidación, la conductividad hidráulica saturada (Ks), permeabilidad de aire (Ka), contenidos de carbono orgánico (CO), textura y alofán. Se estimó la conductividad hidráulica