Temporal evolution of soil erodibility: assessment of explanatory factors, and consequences on erosion modelling. An example from the Beauce area, France

Darboux, Frédéric

Temporal evolution of soil erodibility: assessment of explanatory factors, and consequences on erosion modelling. An example from the Beauce area, France

2012

Darboux, Frédéric

Soil erodibility is a key parameter in soil erosion models. Usually, water erosion models takeerodibility as a constant for a given soil. However, many studies showed that erodibility changesduring the year in relationship with climate. If the seasonal trends are recognized, the underlyingfactors and processes remain unclear. To assess the climatic parameters and soil propertiescausing these variations, a six-month long field monitoring was conducted in the Beauce area(south of the Paris Basin, France). Samples from two soils (a silty clay loam and a silt loam) andfrom two topographic positions were collected at two time scales: monthly, and a few days apartduring the week following significant rain events. Aggregate stability was used as a proxy of soilerodibility. Other measurements were humidity and temperature of soil and air, organic mattercontent, soil texture, water content, microbial biomass, hydrophobicity, and soil crusting. Aggregatestability showed large variability at both time scales. After significant rain events, aggregatestability showed different trends depending on soil type, rain amount and topographic positions.These differences in aggregate stability imply different erodibilities. The results clearly contradictthe common practice of assigning a temporally and spatially-constant erodibility to a given soil. Soiltexture, organic matter and microbial biomass could not precisely explain erodibility changes.However, the post-rain desiccation was significantly related to the erodibility increase at the shorttime step. This result emphasizes the influence of the wetting-drying cycles in soil erodibilityvariation.

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