Quantifying the rate and depth dependence of bioturbation based on optically-stimulated luminescence (OSL) dates and meteoric 10Be

Michelle O. Johnson*, Simon M. Mudd, Brad Pillans, Nigel A. Spooner, L. Keith Fifield, Mike J. Kirkby, Manuel Gloor

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    46 Citations (Scopus)

    Abstract

    Both the rate and the vertical distribution of soil disturbance modify soil properties such as porosity, particle size, chemical composition and age structure; all of which play an important role in a soil's biogeochemical functioning. Whereas rates of mixing have been previously quantified, the nature of bioturbation's depth dependence remains poorly constrained. Here we constrain, for the first time, the relationship between mixing rate and depth in a bioturbated soil in northeast Queensland, Australia using a novel method combining OSL (optically-stimulated luminescence) ages and meteoric beryllium-10 (10Be) inventories. We find that the best fit mixing rate decreases non-linearly with increasing soil depth in this soil and the characteristic length scale of 0.28m over which the mixing coefficient decays is comparable to reported rooting depth coefficients. In addition we show that estimates of surface mixing rates from OSL data are highly dependent on erosion rate and that erosion rate must be constrained if accurate mixing rates are to be quantified. We calculate surface diffusion-like mixing coefficients of 1.8×10-4 and 2.1×10-4m2yr-1 for the studied soil for two different estimates of soil erosion.

    Original languageEnglish
    Pages (from-to)1188-1196
    Number of pages9
    JournalEarth Surface Processes and Landforms
    Volume39
    Issue number9
    DOIs
    Publication statusPublished - Jul 2014

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