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Depth-dependent soil mixing persists across climate zones

April 7, 2020

Soil mixing over long (>102 y) timescales enhances nutrient fluxes that support soil ecology, contributes to dispersion of sediment and contaminated material, and modulates fluxes of carbon through Earth’s largest terrestrial carbon reservoir. Despite its foundational importance, we lack robust understanding of the rates and patterns of soil mixing, largely due to a lack of long-timescale data. Here we demonstrate that luminescence, a light-sensitive property of minerals used for geologic dating, can be used as a long-timescale sediment tracer in soils to reveal the structure of soil mixing. We develop a probabilistic model of transport and mixing of tracer particles and associated luminescence in soils and compare with a global compilation of luminescence versus depth in various locations. The model–data comparison reveals that soil mixing rate varies over the soil depth, with this depth dependency persisting across climate and ecological zones. The depth dependency is consistent with a model in which mixing intensity decreases linearly or exponentially with depth, although our data do not resolve between these cases. Our findings support the long-suspected idea that depth-dependent mixing is a spatially and temporally persistent feature of soils. Evidence for a climate control on the patterns and intensities of soil mixing with depth remains elusive and requires the further study of soil mixing processes.

Citation Information

Publication Year 2020
Title Depth-dependent soil mixing persists across climate zones
DOI 10.1073/pnas.1914140117
Authors Harrison J. Gray, Amanda Keen-Zebert, David Furbish, Gregory E. Tucker, Shannon A. Mahan
Publication Type Article
Publication Subtype Journal Article
Series Title PNAS
Index ID 70209678
Record Source USGS Publications Warehouse
USGS Organization Crustal Geophysics and Geochemistry Science Center; Geosciences and Environmental Change Science Center

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