Impact of wetting-drying cycles on the hydro-mechanical behaviour of vegetated soil

Abstract

Climate change strongly affects the hydro-mechanical properties of soil. Due to drought and heavy rains the soil is subjected to severe hydro-mechanical loads, that, in turn, alter the microstructure of the soil. The most affected area is the so-called vadose zone, the layer of soil situated between the ground surface and the water table. Here the presence of vegetation has a strong impact, related to the elongation/expansion of the root architecture and the hydro-mechanical interactions with soil. Additionally, the presence of plant roots facilitate the evapotranspiration process from deeper soil layers.

The research presents an experimental investigation, aimed to reproduce the typical hydro-mechanical conditions as found in the vadose zone in controlled laboratory conditions. Drying-wetting cycles are induced in soils samples, where maize plants are free to sprout and develop as well as in reference non-vegetated samples. The water content and distribution within the soil matrix are studied through 4D (3D+time) in-vivo x-ray computed tomography and effects on the soil-root microstructure are quantified with 3D image analysis. Those are correlated with above ground measurements such as fluorescence (through a spectroradiometer) that, in turn, provides leaf water potential, and the stomatal conductance that controls the evapotranspiration.