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This article in SSSAJ

  1. Vol. 76 No. 5, p. 1685-1695
     
    Received: Jan 13, 2012
    Published: September 12, 2012


    * Corresponding author(s): mandy.williams@unlv.edu
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doi:10.2136/sssaj2012.0021

Biological Soil Crusts in the Mojave Desert, USA: Micromorphology and Pedogenesis

  1. Amanda J. Williams *,
  2. Brenda J. Buck and
  3. Mengesha A. Beyene
  1. formerly at Dep. of Geoscience currently at School of Life Sciences Univ. of Nevada, Las Vegas 4505 S. Maryland Pkwy. Las Vegas, NV 89154-4004
    Dep. of Geoscience Univ. of Nevada, Las Vegas 4505 S. Maryland Pkwy. Las Vegas, NV 89154-4010
    formerly at Dep. of Geoscience Univ. of Nevada, Las Vegas 4505 S. Maryland Pkwy. Las Vegas, NV 89154-4010 currently at SES Group & Associates, LLC Turner-Fairbank Highway Research Center/FHWA 6300 Georgetown Pike McLean, VA 22101

Abstract

Biological soil crusts (BSCs) are bio-sedimentary complexes that play critical ecological roles in arid landscapes; however, the interactions between component biota and sediments are poorly understood. A detailed micromorphological investigation of BSC development and crust microstructure in the Muddy Mountains Wilderness Area, Nevada, examined features in thin section using petrographic microscopy, light microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. The >1800 microscopic observations were linked to crust macroscale features and soil geomorphology. Complex bio-sedimentary structures of BSCs reflect a dynamic genetic history and diverse formative processes, including: (i) stabilization and authigenic mineral precipitation; (ii) wetting–drying and expansion–contraction; (iii) dust capture; (iv) microscale mass wasting; and (v) vesicular (Av) horizon formation. A new conceptual model for hot deserts illustrates how these processes co-develop with BSC succession, during countless wet–dry cycles, to build up pinnacle microtopography while simultaneously forming Av horizons in the bio-rich and bio-poor zones. Complex surficial and internal bio-sedimentary structures, which vary as a function of crust morphology, trap surface water for uptake by crust organisms, while dust influx provides a source of nutrients. These phenomena influence landscape-scale water dynamics and biogeochemical cycling, increasing the availability of soil resources during times of biotic stress. Biological soil crusts uniquely facilitate the accumulation, morphology, and ecosystem function of dust and should, therefore, be considered critical agents in arid pedogenesis and landscape development.

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Copyright © 2012. Copyright © by the Soil Science Society of America, Inc.