How lysimetric monitoring of Technosols can contribute to understand the temporal dynamics of the soil porosity

Soil poral architecture controls soil functioning and is submitted to temporal changes. The monitoring of soil structure dynamics is complicated by inherent technical constraints in its measurement that are either punctual or complex. In this study, four soils, from a natural one to incrementally anthropized (including three Technosols: Spolic Toxic, Terric Transportic, Spolic Garbic Hydric), have been studied. Seven 2-m3 lysimetric columns have been setup to compare planted and non-planted treatments over 3 to 6 years. Data on the water balance and the hydrodynamics were continuously acquired. Differences were observed between the various soils as a function of their texture. The presence of vegetation also led to significant differences, especially in hot periods, between the vegetated and the bare soils treatments: the amount of water stored into the soil was up to 210 L m− 2 higher for bare soil. Furthermore, the analysis of the “critical water storage capacity” highlighted differences in the hydrodynamics at two time scales. For vegetated soils, similar seasonal variations depending on the climatic conditions were observed for all soils, with higher SCRIT values in cold periods compared to hot periods (differences were up to 190 L m− 2). These results were attributed to roots development over the climatic year that decreases water storage capacity and increases preferential flows. Besides, significant trend evolution was also observed but only for the youngest i.e. the most anthropized soils. Their total water storage capacity decreased down to 52%. It is possibly due to soil compaction, the increase of pore connectivity related to root development and the formation of organo-mineral associations. Our work promotes the association of monitored lysimeters as tool and the study of soils within a gradient of anthropization in order to describe a pedogenetic process like the dynamics of soil porosity.