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This article in SSSAJ

  1. Vol. 75 No. 4, p. 1330-1342
     
    Received: July 20, 2010
    Published: July, 2011


    * Corresponding author(s): albert@eeza.csic.es
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doi:10.2136/sssaj2010.0283

Two-Dimensional Porosity of Crusted Silty Soils: Indicators of Soil Quality in Semiarid Rangelands?

  1. I. Miralles-Melladoa,
  2. Y. Cantónb and
  3. A. Solé-Benet *c
  1. a Estación Experimental de Zonas Aridas CSIC04120-Almería, Spain
    b Dep. of Soil Science, University of Almería, 04120-Almería, Spain
    c Estación Experimental de Zonas Aridas CSIC04120-Almería, Spain

Abstract

Little is known about the morphological characteristics of pores in soil crusts. The objective was to characterize the two-dimensional (2D) porosity (amount, shape, size, and area of pores) of soil crusts to ascertain their potential as indicators of soil quality for natural crusted soils. The 2D-porosity was described in thin sections and measured by image analysis of polished resin-impregnated soil blocks. Physical soil crust and incipient biological soil crusts appear to be the lowest-quality soils in terms of number of pores (average of 131–133 cm−1) and area occupied by pores or meso-macroporosity (3.5–4.2%). Their most abundant pore types were small unconnected rounded pores. Soil crust infiltration coefficients (65–72% annual) were among the lowest and their high erosion rates (81–204 g m−2 yr−1) were not only due to their lower total porosity, but also to their pore shapes and sizes. Biological soil crusts appear on higher-quality soil, where the higher the organic C content, the more evolved the soil crust is (with lichens and cyanobacteria). Such soil crusts have better developed pore-systems with specific meso- and macropore morphologies, for example, large, interconnected elongated and irregular pores. Biological soil crusts (BSCs) dominated by lichens have the largest meso-macroporosity (up to 23.65%) due to the predominance of elongated pores. In many cases, infiltration is low (46–57%) because the biological crusts are somewhat detached from the soil underneath, but the armouring effect decreases erosion rates (7–23 g m−2 yr−1). Soil crust pore numbers, size, and shape were useful indicators of soil quality.

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