The water-level fluctuation zone (WLFZ) of the Three Gorges Reservoir (TGR) experiences seasonal submergence and exposure, resulting in soil structure degradation and intensified erosion. This study investigated how flooding duration affects root development and the erosion resistance of root–soil complexes in the WLFZ of the TGR. Two representative herbaceous species were chosen for this study: Xanthium sibiricum, an annual with a taproot system, and Cynodon dactylon, a perennial with a fibrous root system. Root traits, soil erodibility K-value, shear strength, and soil texture were measured from plant and soil samples collected at different flooding durations (145–175 m elevations). Our results showed that prolonged flooding significantly suppressed root growth, particularly in the 145–155 m zone, where root length density and root tips were markedly reduced (p < 0.05). Soil erodibility increased with flooding duration, with erodibility K-values ranging from 0.050 ± 0.002 to 0.062 ± 0.001 t·hm²·h/(MJ·mm·hm²), while shear strength declined correspondingly. Textural shifts from silty loam to silt were observed at zones experiencing extended flooding, contributing to aggregate instability and decreased internal friction angles. Notably, Cynodon dactylon demonstrated superior soil reinforcement capacity compared to Xanthium sibiricum, with its root volume and surface area significantly correlated with reduced K-values (p < 0.01) and enhanced shear strength (p < 0.001), enabling it to better prevent bank erosion under flooding conditions. These findings underscore the importance of root morphological traits in maintaining soil stability under hydrological stress and highlight the potential of perennial fibrous-rooted species for vegetation-based erosion control in fine-textured riparian zones. This study provides a theoretical basis and practical reference for ecological restoration in the WLFZ of the TGR and similar environments.

Improved soil phosphorus (P) management can be achieved through an understanding of regional soil–P interactions and their relation to soil properties. To this end, soil samples from different use types (paddy soils, dry farmland soils, forest soils, and urban green land soils) were collected from 10 sites across the west to the east of Sichuan Basin, China. These samples were analyzed to determine their P sorption properties and physical and chemical compositions. P sorption was described using a modified Freundlich equation. The results demonstrated a gradient in P sorption within the basin, characterized by higher values in urban areas and a west-to-east decrease trend, along with the null-point values of soil sorption–desorption equilibrium. This variation was linked to the extensive use of P fertilizer, which altered soil particle surface conditions and significantly reduced both the quantity and rate of subsequent fertilizer sorption. Furthermore, P sorption was found to be correlated with the soil clay fraction, amorphous aluminum oxides, and soil organic matter contents. Urban expansion and accelerated erosion of productive agricultural land increase mean soil particle size and may decrease soil P holding and retention capacity. As preliminary deterioration in soil properties was found, conservative soil management is needed to address the potential threats of soil degradation in the central Sichuan Basin.

Soil erosion is a global environmental problem related to anthropogenic activities which are influenced by natural factors. The sloping cultivated lands, with serious soil erosion, constitute a significant proportion of the landscape in the remote mountain regions of southwestern China. The traditional soil conservation strategy, involving a certain height of lynchets on the edge of the terracing hedgerows of the sloping lands, plays an effective part in soil and water conservation. A typical sloping landscape with a lynchet of terracing hedgerows was chosen in this study. The objective of this study was to explore soil particle size fraction and spatial redistribution of ¹³⁷Cs in sloping landscapes with different lynchet heights of terracing hedgerows. The results showed that fine-grained sediments were deposited in front of the lynchet of terracing hedgerows, especially particle sizes grouped at <0.002 mm clay and 0.002–0.02 mm silt. The ¹³⁷Cs concentration profiles of the lynchet from the upper to the lower sloping landscape showed first increasing and then decreasing trends when the soil depth increased. ¹³⁷Cs inventory generally increased along with the whole sloping landscapes. Moreover, the results suggested that the mean ¹³⁷Cs inventory and erosion rate could be represented by the average value of the middle slope position. The highest value of annual erosion modulus reached 4917.06 t km⁻² a⁻¹ on the upper site of the sloping lands. Moreover, the annual erosion modulus was synchronously reduced from the upper to the lower sloping landscape and the erosion rate had a similar trend. Meanwhile, the K values of soil erodibility changed from 0.0338 t hm² h (hm⁻² MJ⁻¹ mm⁻¹) to 0.0375 t hm² h (hm⁻² MJ⁻¹ mm⁻¹) along the slope length. There was a logarithmic relationship between the K value and the ¹³⁷Cs inventory. Therefore, it is useful to study spatial patterns of soil erosion in different slope positions with different heights of lynchet of terracing hedgerows of the whole sloping landscape. Moreover, it is important to implement a soil conservation strategy in the remote mountain regions of China.