La degradación de los bosques de altura del centro de Argentina reduce su capacidad de almacenamiento de agua

Abstract

R������. La capacidad del suelo de almacenar y regular el flujo de agua depende en gran medida de su su tasa de infiltración y profundidad. Los disturbios como el pastoreo y el fuego son moduladores fuertes del sistema vegetación-suelo, ya que son capaces de alterar la tasa de infiltración y la profundidad del suelo. En sistemas montanos estacionales, esto repercute sobre la capacidad de liberar lentamente el agua almacenada hacia el caudal de los arroyos. Nos propusimos indagar si las variaciones en la estructura de la vegetación, debidas en su mayoría al pastoreo y al fuego, de los bosques de altura de Polylepis australis Bi�er de las sierras de Córdoba se asocian a variaciones en las propiedades del suelo en general y, en particular, a aquellas que regulan la capacidad de almacenar agua. Para abarcar la variabilidad completa de estructura de la vegetación seleccionamos 28 sitios distribuidos en tres establecimientos con distintos manejos, y restringimos las variaciones topográficas. No detectamos asociaciones entre la estructura de la vegetación y la topografía; es decir, en general, logramos restringir el efecto topográfico. Por otro lado, aquellos sitios con vegetación más estructurada presentaron suelos con menor densidad aparente y mayor contenido de materia orgánica y capacidad de campo. En relación a la capacidad de almacenamiento de agua, los suelos más profundos y con mayor tasa de infiltración fueron los menos densos, con mayor contenido de materia orgánica y mayor capacidad de campo, asociados a una vegetación más estructurada. Es decir, mientras más conservado se encuentra el sistema vegetación-suelo de los bosques de P. australis, mayor cantidad de agua puede ingresar al suelo y ser almacenada. En consecuencia, las alteraciones del sistema vegetación-suelo, dadas principalmente por el pastoreo y el fuego, reducen la capacidad de almacenar agua de los bosques de altura del centro de la Argentina.[Palabras clave: Polylepis australis, tasa de infiltración, profundidad del suelo, estructura de la vegetación, suelo, montañas, pastoreo, fuego, disturbio, ecohidrología] A�������. The degradation of highland woodlands of central Argentina reduces their soil water storage capacity. 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 Bi�er 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. W...

Water storage dynamics across different types of vegetated patches in rocky highlands of central Argentina

“…It has even been suggested that a simplification of vegetation structure and a reduction of vegetation cover may reduce fog interception decreasing net precipitation (Gomez‐Peralta, Oberbauer, McClain, & Philippi, ; Ponette‐González et al, ). Thus, changes in vegetation structure associated to grazing and fire disturbances described for our study area (Poca et al, ) could be promoting a lesser interception of fog with consequences for the water balance.…”

“…Even though this area is characterized by relatively shallow soils (~1 m) and soil depth is naturally variable due to topography and micro roughness of the bedrock, disturbances act in synergy with these natural variations to reduce soil depth or even completely eliminate the soil profile, forming stonelands, which are clearly distinct from granitic outcrops (Cingolani et al, , ; Poca et al, ). Grazing and fire also reduce soil organic matter content, field capacity, and infiltration rate, and increase soil impedance and bulk density (Poca et al, ). Additionally, these disturbances reduce the size and increase the mortality of P .…”

“…The landscape consists of a mosaic of patches with variable vegetation structure within a matrix of granitic outcrops, including Polylepis australis Bitter woodlands, shrublands, tussock grasslands, grazing lawns, fernlands, and stonelands (Cingolani et al, 2003(Cingolani et al, , 2008(Cingolani et al, , 2013(Cingolani et al, , 2014Renison et al, 2006;Poca et al, 2018). All these vegetation types are, at least in part, the result of long-term disturbance by grazing and fire (Cingolani et al, 2003(Cingolani et al, , 2008(Cingolani et al, , 2013(Cingolani et al, , 2014.…”

“…All these vegetation types are, at least in part, the result of long-term disturbance by grazing and fire (Cingolani et al, 2003(Cingolani et al, , 2008(Cingolani et al, , 2013(Cingolani et al, , 2014. Even though this area is characterized by relatively shallow soils (~1 m) and soil depth is naturally variable due to topography and micro roughness of the bedrock, disturbances act in synergy with these natural variations to reduce soil depth or even completely eliminate the soil profile, forming stonelands, which are clearly distinct from granitic outcrops (Cingolani et al, 2008(Cingolani et al, , 2013Poca et al, 2018). Grazing and fire also reduce soil organic matter content, field capacity, and infiltration rate, and increase soil impedance and bulk density (Poca et al, 2018).…”

“…Moreover, grazing and fire disturbance shape vegetation structure and soil properties of those patches, contributing to set up a complex and contrasting landscape. These disturbances can even trigger strong erosion, transforming the vegetated patches into rocky areas with small spots of soil (Cingolani, Cabido, Renison, & Solís Neffa, 2003;Cingolani, Renison, Tecco, Gurvich, & Cabido, 2008;Cingolani et al, 2013Cingolani et al, , 2014Renison, Hensen, Suarez, & Cingolani, 2006;Renison et al, 2010;Renison et al, 2015;Poca, Cingolani, Gurvich, Whitworth-Hulse, & Saur Palmieri, 2018). We have previously shown that as long-term grazing and fire simplified vegetation structure, soil depth, organic matter content, field capacity, and infiltration rate were reduced, whereas soil impedance and bulk density increased.…”