Quantification par approche micromorphologique couplée à de l’analyse d’images de l’effet de la mise en culture et de l’apport de matières organiques sur l’intensité et la dynamique des processus de lessivage et de bioturbation à l’échelle pluri décennale

Abstract : The intensity at which soils provide ecosystem services are function of soil properties that permanently evolved according to numerous processes. Lessivage and bioturbation are of crucial importance as they imply the clay size fraction but are still poorly characterized. This study aims at i) developing a digital 2D image analysis method to quantify both processes intensity, ii) quantifying the effect of two centuries of continuous cultivation and of a decade of organic amendments spreading on their intensity, and iii) characterizing their dynamics. We succeeded in quantifying those processes by carefully considering different levels of soil organization while combining a colorimetric and a textural approach. The percentage volume of worm-worked soil since 10 000 to 15 000 years is 65% at 40 cm depth and between 20 and 30% at 150 cm depth that corresponds to a soil mass flow of 6 500 t.ha-1, i.e. 1 700 t.ha-1 of clay size fraction. Illuviation is responsible for a clay size fraction mass flow of 1 100 t.ha-1. On a time scale as short as two centuries, cultivation was found to induce i) a change of the soil poral network characteristics until 1 meter depth, ii) a modification of the structure of the worm-worked soil volume, and finally iii) an increase of the lessivage intensity. A decade of organic matter spreading tended to lower the intensity of lessivage. Finally, our study points out the fact that soils are highly reactive and that our method may be particularly helpful to predict soil evolution while facing climate change among others.
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Ophélie Sauzet. Quantification par approche micromorphologique couplée à de l’analyse d’images de l’effet de la mise en culture et de l’apport de matières organiques sur l’intensité et la dynamique des processus de lessivage et de bioturbation à l’échelle pluri décennale. Science des sols. Université Paris-Saclay, 2016. Français. ⟨NNT : 2016SACLA024⟩. ⟨tel-01588074⟩

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