Preprints
https://doi.org/10.5194/esurf-2021-22
https://doi.org/10.5194/esurf-2021-22

  01 Apr 2021

01 Apr 2021

Review status: this preprint is currently under review for the journal ESurf.

Vegetation and climate effects on soil production, chemical weathering, and physical erosion rates

Mirjam Schaller and Todd Alan Ehlers Mirjam Schaller and Todd Alan Ehlers
  • University of Tuebingen, Department of Geosciences, Schnarrenbergstrasse 94-96, 72076 Tuebingen, Germany

Abstract. Weathering of bedrock to produce regolith is essential for sustaining life on Earth and global biogeochemical cycles. The rate of this process is influenced not only by tectonics, but also by climate and biota. Here we investigate these interactions with new observations of soil production, chemical weathering, and physical erosion rates from the large climate and vegetation gradient of the Chilean Coastal Cordillera (26° to 38° S). These findings are compared to a global compilation of published data from similar settings. The four Chilean study areas span (from North to South): arid (Pan de Azúcar), semi-arid (Santa Gracia), mediterranean (La Campana) and temperate humid (Nahuelbuta) climate zones. We test the hypotheses that: 1) soil production as well as chemical weathering rates increase with increasing mean annual precipitation; 2) physical erosion rates stabilize as vegetation cover increases; and 3) the contribution of chemical weathering to total denudation is constant over the climate gradient.

We find observed soil production rates range from ~7 to 290 t/(km2 yr) and are lowest in the sparsely vegetated and arid North, increase southward toward the vegetated mediterranean climate, and then decrease further South in the temperate humid zone. This trend is discussed and compared with global data from similar catchments underlain by granitic lithologies. Calculated chemical weathering rates range from zero in the arid North to a high value of 211 t/(km2 yr) in the mediterranean zone. Chemical weathering rates are comparable in the semi-arid and temperate humid zones (~20 t/(km2 yr). Physical erosion rates are low in the arid zone (~11 t/(km2 yr)) and increase towards the South (~ 40 t/(km2 yr)). Combined total chemical weathering and physical erosion rates indicate that denudation rates are lowest in the arid North and highest in the Mediterranean climate zone. The contribution of chemical weathering to total denudation rates increases and then decreases with increasing mean annual precipitation from North to South. The observation that the calculated chemical weathering rates in the southernmost location, with the highest mean annual precipitation and the highest chemical index of alteration, are not the highest of all four study areas is found to be consistent with the global data analysis.

Mirjam Schaller and Todd Alan Ehlers

Status: open (until 23 May 2021)

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Mirjam Schaller and Todd Alan Ehlers

Mirjam Schaller and Todd Alan Ehlers

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Short summary
Soil production, chemical weathering, and physical erosion rates from the large climate and vegetation gradient of the Chilean Coastal Cordillera (26° to 38° S) are investigated. We find observed rates are generally lowest in the sparsely vegetated and arid North, increase southward toward the vegetated mediterranean climate, and then decrease further South in the temperate humid zone. This trend is compared with global data from similar soil-mantled hillslopes underlain by granitic lithologies.