• Badlands in the Tabernas Basin, Betic Chain

      Calvo-Cases, Adolfo; Harvey, Adrian M.; Alexander, Roy; Cantón, Yolanda; Lázaro, Roberto; Solé-Benet, Albert; Puigdefábregas, Juan; University of Valencia, University of Liverpool, University of Chester, University of Almería, CSIC, Almería (Springer, 2014-04-19)
      The complex badland landscape at Tabernas results from a combination of relief amplitude generated by tectonic uplift since the Pliocene and reactivated several times during the Pleistocene, the properties of the Tortonian sedimentary rocks and a predominantly arid climate. The landscape is dominated by deep incision of the main river systems, which continues in part of the headwater tributaries, and characterized by contrasting slope morphologies and a variety of microecosystems. The Tabernas badlands exhibit a diversity of landforms resulting from the combination of multi-age soil surface components that allow a variety of processes to operate at different rates. These are dominated by rilling and shallow mass movements on south-facing hillslopes. On old surfaces and north-facing hillslopes, where biological components are present, overland flow with variable infiltration capacity and low erosion rates prevail. Incision in the gully bottoms occurs in the most active areas.
    • Biocrusts and catchment asymmetry in Tabernas Desert (Almeria, Spain)

      Lázaro, Roberto; Calvo-Cases, Adolfo; Rodriguez-Caballero, Emilio; Arnau-Rosalén, Eva; Alexander, Roy; Rubio, Consuelo; Cantón, Yolanda; Solé-Benet, Albert; Puigdefábregas, Juan; Estacion Experimental de Zonas Aridas (CSIC); Universitat de Valencia; Universidad de Almeria; Manchester Metropolitan University; University of Chester (Elsevier, 2021-10-15)
      Catchment asymmetry is a fairly frequent phenomenon on a global scale but the main causes leading to its formation are still not well understood. Where the intervention of structural or tectonic causes is not relevant, asymmetry seems to result from differential erosion between opposite slopes that flow into the same channel, which is frequently associated with contrasted biocrust and/or vegetation covers. Biocrusts are known to be important surface stabilizing agents. However, their geomorphological consequences at the landscape scale are little known. In this study we combined field measurements with digital elevation models and image analysis to determine whether catchment asymmetry in the Tabernas Desert (semi-arid SE of Spain) is a local or general phenomenon, and to explore the main factors determining asymmetry occurrence, magnitude and direction. We pay special attention to the role of biocrusts. We found that catchment asymmetry is a very common phenomenon in the area; only 25% of the catchments are symmetrical, while approximately 40% present asymmetry with the relatively shady hillslope having a lower gradient, and 35% with that hillslope being the steeper. Solar radiation reaching the soil, surface area and channel gradient in the considered catchment stretch, as well as the total catchment area upstream from the lower point of the considered stretch were the main abiotic factors controlling the formation of the asymmetry. Microclimatic differentiation due to differences in radiation input caused by the uneven topography favoured the relative stabilization of the shadier hillslope and its colonization by biocrusts and later by plants. The effect of the biocrusts and vegetation protection against water erosion on shadier hillslopes is often stronger than that of the set of abiotic factors and gives rise to asymmetries with lower gradients in the shady hillslope by promoting lateral displacement of the channel. We hypothesised that the opposite pattern, with the sunnier hillslope having a lower gradient, occurs when abiotic factors control the development of asymmetry formation. In these conditions, the effect of biocrusts and plants would act in the opposite direction. We propose a conceptual model of feedbacks generating catchment asymmetry, with biocrust playing a crucial role.
    • Catchment asymmetry in Tabernas Desert (Almería, Spain)

      Lazaro, R.; Calvo-Cases, A.; Rodriguez-Caballero, E.; Arnau-Rosalén, Eva; Alexander, R.; Rubio, C.; Cantón, Y.; Solé-Benet, A.; Puigdefábregas, J.; Estación Experimental de Zonas Aridas (CSIC), Almería, Spain; Inter-University Institute for Local Development, Department of Geography, Universitat de València. Spain; School of Science & Environment, Manchester Metropolitan University, United Kingdom; Department of Geography & International Development, Univ. of Chester, UK; Departamento de Agronomia, Universidad de Almería, Spain
      Abstract and e-Poster presented at Geoecology and Desertification, from physical to human factors. International Symposium in memory of Prof Juan Puigdefabregas (EcoDesert) Almería, February 2019.