Quantifying the controls on potential soil production rates: a case study of the San Gabriel Mountains, California
The potential soil production rate, i.e., the upper limit at which bedrock can be converted into transportable material, limits how fast erosion can occur in mountain ranges in the absence of widespread landsliding in bedrock or intact regolith. Traditionally, the potential soil production rate...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-08-01
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| Series: | Earth Surface Dynamics |
| Online Access: | https://www.earth-surf-dynam.net/5/479/2017/esurf-5-479-2017.pdf |
| Summary: | The potential soil
production rate, i.e., the upper limit at which bedrock can be converted into
transportable material, limits how fast erosion can occur in mountain ranges
in the absence of widespread landsliding in bedrock or intact regolith.
Traditionally, the potential soil production rate has been considered to be
solely dependent on climate and rock characteristics. Data from the San
Gabriel Mountains of California, however, suggest that topographic steepness
may also influence potential soil production rates. In this paper I test the
hypothesis that topographically induced stress opening of preexisting
fractures in the bedrock or intact regolith beneath hillslopes of the San
Gabriel Mountains increases potential soil production rates in steep portions
of the range. A mathematical model for this process predicts a relationship
between potential soil production rates and average slope consistent with
published data. Once the effects of average slope are accounted for, a small
subset of the data suggests that cold temperatures may limit soil production
rates at the highest elevations of the range due to the influence of
temperature on vegetation growth. These results suggest that climate and rock
characteristics may be the sole controls on potential soil production rates
as traditionally assumed but that the porosity of bedrock or intact regolith
may evolve with topographic steepness in a way that enhances the persistence
of soil cover in compressive-stress environments. I develop an empirical
equation that relates potential soil production rates in the San Gabriel
Mountains to the average slope and a climatic index that accounts for
temperature limitations on soil production rates at high elevations. Assuming
a balance between soil production and erosion rates on the hillslope scale, I
illustrate the interrelationships among potential soil production rates, soil
thickness, erosion rates, and topographic steepness that result from the
feedbacks among geomorphic, geophysical, and pedogenic processes in the San
Gabriel Mountains. |
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| ISSN: | 2196-6311 2196-632X |