Global rates of soil production independent of soil depth

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Emma Jayne Harrison, Jane Willenbring , Gilles Brocard 


Accelerated rates of soil erosion threaten the stability of ecosystems1, nutrient cycles2, and global food supplies3 if the processes that produce soil cannot keep pace. Over millennial timescales, the rate of soil production is thought to keep pace with the rate of surface erosion through negative feedbacks between soil thickness and the rate at which soil is produced from the underlying mineral substrate4,5. This paradigm in the Earth Sciences holds that some underlying mechanism lowers the rate of soil production when soil is thick and increases the rate of soil production when soils are thin. This dynamic balance lends support to two observations: First, soil covers >90% of Earth’s ice-free surface (NRCS) despite global erosion rates that vary by three orders of magnitude3 and second, the thickness of soils on Earth exists within a relatively narrow range even in old and deeply weathered landscapes7. However, the actual coupling mechanism between soil thickness and depth is unknown, and the functional form of the relationship is debated. Here, we question whether this balance exists and whether the apparent negative feedback instead arises from a computational artefact of how soil production rates are calculated in landscapes with changing erosion rates. As evidence, we compared sites that have likely experienced constant erosion rates and climate over geologic timescales with sites that may experience transient erosion responses to environmental change in a global compilation of soil production versus soil thickness. We conclude that soil production resists self-arresting behavior in some locations and is uniformly slow in arid and semi-arid settings - independent of soil depth. This result has drastic consequences for soil sustainability in the context of anthropogenically accelerated soil erosion such that an acceleration in modern erosion may not give rise to a concomitant, matched rise in soil production.



Physical Sciences and Mathematics


Erosion, Soils, Soil Production


Published: 2021-01-02 20:07

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