Quantification of red soil macropores affected by slope erosion and sediment using computed tomography

• Published in: Vadose zone journal 2023-11, Vol.22 (6), p.n/a
• Main Authors: Zhang, Si‐Yi, He, Bin, Hao, Beibei, Lv, Depeng
• Format: Article
• Language: English
• Subjects: Computed tomography; Cores; Gullies; Hydrology; Macroporosity; Moisture content; Precipitation; Rain; Sediment; Sediments; Soil analysis; Soil erosion; Soil infiltration; Soil properties; Soil structure; Soil water; Tomography; Vegetation; Water erosion; Water infiltration
• ISSN: 1539-1663; 1539-1663
• DOI: 10.1002/vzj2.20276

Soil structure is an important factor interacting with soil erosion and sediment processes. However, few studies have focused on the relationship between soil macroporosity and soil erosion across different terrains. The aim of this study was to quantify and compare soil properties and macroporosity characteristics in collapsing gully areas and to explore their impact on the formation and development of collapsing gullies. Soil cores were excavated at different positions of a typical collapsing gully and then scanned to analyze soil macropores. Soil properties and saturated hydraulic conductivity were also investigated. The results showed that the contents of sand, silt, and clay, the mean weight diameter of aggregates, and the infiltrate rates varied at different positions. The valley had the greatest macroporosity (1.09% ± 0.33%), the number (5919 ± 703), volume (1468 ± 194 mm3), and surface area (10.4 ± 2.6 m2) of macropores, as well as the mean volume (16.8 ± 7.4 mm3) of macropores >1 mm3, whereas these indices were lowest at the slope (0.15% ± 0.14%, 1189 ± 747, 266 ± 188 mm3, 1.7 ± 1.4 m2, and 10.6 ± 2.9 mm3, respectively). The macroporosity and the number of macropore decreased with increasing depth but were also influenced by the erosion and sediment processes. The processes of sediment and the roots of vegetation also influenced the orientation of the macropores. Macropore characteristics at different sites of the collapsing gullies affected the soil water infiltration and hydraulic conductivity and further affected the processes of water erosion and mass erosion. Core Ideas The architecture of soils at an erosive collapsing gully was studied using CT. The ridge had middle macropores and was collapsing due to high infiltration. Soil at the slope had low macroporosity and Ksf and was eroded by runoff. Sediment at the valley had highest macroporosity and was eroded by subsurface flow. Erosion and sediment processes interacted with soil structure properties. Core Ideas The architecture of soils at an erosive collapsing gully was studied using CT. The ridge had middle macropores and was collapsing due to high infiltration. Soil at the slope had low macroporosity and Ksf and was eroded by runoff. Sediment at the valley had highest macroporosity and was eroded by subsurface flow. Erosion and sediment processes interacted with soil structure properties.