Soil pore structure dynamics under steady-state wetting-drying cycle

Abstract

The soil pore space is an arena for processes responsible for numerous critical soil functions. We sampled 15 soil samples from 3 horizons (A, E, Bt) and performed a detailed X-ray microtomography (XCT) imaging study of the full wetting-drying (W-D) curve. This way, we revealed the dynamics of soil pore structure under slow water changes for Albic Retisols. In total, our analysis is based on 135 3D tomography scans (9 soil moisture points for each sample). Using the obtained structural information in the form of binary pore-solid segmentations, we were able not only to visualize structural dynamics (which showed significant changes within the soil at ∼10 µm – 3 mm pore sizes range) but also computed major classical morphological metrics. The analysis of these parameters and conceptual model of structural behavior revealed that after the W-D cycle the studied soil degraded in general. This is contrary to the prevailing previous findings for mainly compacted soils where W-D cycles led to structural improvements. We discussed the major implications of these findings and outlined a possibility to deepen our understanding of soil structure-function relationships, including dynamic hydraulic soil properties and 3D soil structure digital model.