Uso de la tierra y ambiente local de descomposición en el Chaco Semiárido de Córdoba, Argentina

Abstract

R������.El cambio en el uso de la tierra es un proceso clave debido a sus efectos directos sobre la identidad y la estructura de la vegetación. En el Chaco Semiárido se conoce poco acerca del impacto de los cambios en la vegetación sobre los procesos relacionados con el ciclado de nutrientes (e.g., la descomposición). En este trabajo analizamos si las modificaciones en la vegetación, producto de distintas intensidades en el uso de la tierra, producen cambios en las condiciones del ambiente local, y si estos cambios afectan el patrón de descomposición de dos materiales comunes. En las configuraciones vegetales analizadas encontramos que el cambio en el uso de la tierra tiene un impacto evidente sobre la cobertura vegetal, aunque no se traduce en cambios consistentes en el ambiente local de descomposición. Específicamente, encontramos que el incremento en la intensidad de uso se asoció a la disminución de la cobertura vegetal, de la altura de esa cobertura y de la cantidad de broza depositada sobre el suelo. Estas modificaciones estuvieron vinculadas a una disminución del contenido total de C y N en el suelo. Sin embargo, los cambios en la estructura de la vegetación no se relacionaron con los cambios en las condiciones ambientales locales (temperatura y humedad), pese a que se detectaron diferencias en esas variables ambientales entre las distintas configuraciones vegetales. Por su parte, la descomposición fue mayor en aquellos sitios con menor cobertura vegetal, que a su vez, presentaron menor temperatura del aire. Estos resultados sugieren que el cambio en el uso de la tierra tiene un impacto muy evidente sobre la cobertura de la vegetación, pero este impacto no se traduce en cambios consistentes en el ambiente local de descomposición. En estudios futuros será interesante evaluar la contribución de los procesos de degradación abiótica (fotodegradación y fragmentación física) sobre la descomposición y el ciclado de nutrientes.[Palabras clave: controles de descomposición, materiales comunes, carbono, configuraciones vegetales, estructura de la vegetación, clima local] A�������. Land use and local decomposition environment in the Semiarid Chaco of Córdoba, Argentina.Land use change is a key process due to its direct effects on the identity and structure of vegetation. In semiarid Argentinean Chaco, there is scarse information about the consequences of vegetation changes on processes related to nutrient cycling (e.g., decomposition). In this work, we analyse if changes in local climatic conditions due to changes in vegetation structure, related to different land use types, affect decomposition pa�ern of two common materials. We found that land use change has a clear impact on vegetation cover, but this impact is not reflected into a consistent change in local decomposition environment. Specifically, we found that more intensive land use types were related to a decrease in vegetation cover and height and also to less li�er quantity. These changes were associated with lower soil C and N. However, changes in vegetatio...

Not gone with the wind: Vegetation complexity increases seed retention during windy periods in the Argentine Semiarid Chaco

“…The different quadrats where the retention experiment was carried out were characterized by different degrees of vegetation complexity, which in turn was strongly associated with land use regime: the ecosystem type with the most intense long‐term biomass removal (open shrubland) was the one showing the simplest vertical structure, lowest ground cover and a dominance of grasses and S. sellowii in the surface layer. These changes in vegetation structure and ground cover type are consistent with those reported as the consequences of long‐term intense biomass removal by grazing and logging in the semiarid Chaco (Bregaglio, Karlin, & Coirini, ; Cabido et al., , ; Coirini et al., ; Conti & Díaz, ; Conti et al., ; Cuchietti et al., ; De Casenavea, Pelottob, & Protomastro, ; Gardner et al., ).…”

“…Along the transect and every 5 m, we set a 50 cm × 50 cm quadrat (10 quadrats per plot). In each quadrat, we measured the following descriptors of vegetation complexity: ground cover percentage, vertical structure (estimated by the number of vegetation touches on a marked 2‐m pole, Gardner et al., ) and ground cover types (estimated as the percentage of litter, forbs, graminoids and Selaginella sellowii , based on previous studies by Cabido et al., ; Conti et al., ; Conti & Díaz, ; Cuchietti et al., ).…”

“…The Chaco forest — the most extended seasonally dry forest in South America — has experienced important land‐use changes in the last few decades (Cabido, Acosta, Carranza, & Díaz, ; Cabido, Manzur, Carranza, & González Albarracin, ; Grau & Aide, ; Hoyos et al., ). These changes have modified the physiognomy and species composition (Cabido et al., , ; Gardner, Cabido, Valladares, & Díaz, ; Karlin, ) and affected ecosystem processes such as carbon sequestration (Conti & Díaz, ; Conti et al., ), decomposition and nutrient cycling (Cuchietti et al., ), herbivory (Díaz, Acosta, & Cabido, ; Díaz, Cabido, Zak, Martínez Carretero, & Araníbar, ; Tálamo et al., ) and water dynamics (Jobbágy, Nosetto, Santoni, & Baldi, ). Nevertheless, the effect of land‐use change on processes related to ecosystem recovery and resilience, like seed dynamics, is still poorly known.…”

Low resilience at the early stages of recovery of the semi‐arid Chaco forest—Evidence from a field experiment

“…Additionally, our index included not only different intensities of present and past land use (represented as the different ecosystem types), but also the variation of these ecosystem types in time, through a local control. These control plots enabled us to assess the impact of different intensities of land use, confirming the general findings of previous studies (Conti & Díaz, 2013;Conti et al, 2016Conti et al, , 2018Cuchietti et al, 2017;Gardner et al, 1995;Lipoma et al, 2019), and also to identify changes in vegetation composition that were the result of factors different from exclusion, principally variation in precipitation (Supporting Information Appendix 1). High-rainfall periods in the ecosystem of the Chaco forest are supposed to have a synergistic effect with exclusion from grazing (Adamoli et al, 1990;Cabido et al, 1992Cabido et al, , 1994Cotroneo et al, 2018) and it has been suggested that the restoration of degraded arid ecosystems might be achieved in an efficient way by adjusting stocking rates to the occurrence of temporal windows of opportunity (Holmgren & Scheffer, 2001;Meserve et al, 2003).…”

Altitude and species identity drive leaf litter decomposition rates of ten species on a 2950 m altitudinal gradient in Neotropical rain forests

“…Fresh litter (senescent leaves released from the tree) was collected in and around the plots over a period of one year, oven dried at 65℃ and stored. Litter of the two standard species, A. communis and J. ichu , was imported to Costa Rica from collection sites in Central Argentina (Cuchietti et al, ; Vaieretti et al, ).…”