The degradation of highland woodlands of central Argentina reduces their soil water storage capacity

Abstract

Soil water storage capacity and flow regulation relies mostly upon infiltration rate and soil depth. Disturbs such as grazing and fire strongly modulate the vegetation-soil system, and are capable of altering the infiltration rate and soil depth, as well. In mountain seasonal ecosystems, this impacts on soil capacity to slowly release water into streams. We aimed at analyzing if changes in vegetation structure and soil properties, mainly as a consequence of grazing and fire, of highland Polylepis australis Bitter woodlands of Córdoba mountains, also include alterations in general soil properties and, in particular, in those related to soil water storage capacity. In order to encompass the complete variability in vegetation structure we selected 28 sites in paddocks with different managements, restricting topographic variations. We did not find associations between vegetation structure and topographic variables, which indicates we could restrict the topographic variability. Sites with more structured vegetation had soils with lower soil bulk density and higher soil organic matter content and field capacity. Regarding soil water storage capacity, deeper soils with higher infiltration rates were those with more dense soils and higher organic matter content and field capacity, associated to more structured vegetation. This means that while vegetation-soil system of P. australis woodlands is more conserved, the soil presents more opportunities of infiltrating and storing water. Consequently, alterations on the vegetation-soil system, mainly given by grazing and fire, reduce soil water storage capacity of highland woodlands of central Argentina.