The impact of paleoclimatic on the structural strength of loess paleosol sequences and its implications for tillage on the Loess Plateau: A case study from Luochuan profile

Abstract

The structural strength of the Loess-Paleosol Sequence (LPS) and the presence of paleosols within the LPS have significant implications for tillage and understanding past climate conditions. This research investigation sought to examine the structural strengths of the Luochuan (LC) LPS via both triaxial shear and oedometer tests, with the microstructure being further characterized through scanning electron microscopy. Results indicate that the LPS's structural strength tends to increase as burial depth increases. Additionally, the loess layer's structural strength is typically lower than that of the adjacent paleosol layer. The LPS's microstructure experiences considerable transformations with increased burial depth, particularly regarding changes in particle contact relationship, degree of cementation, and pore volume. This shift is characterized by a transition from an overhead structure to a matrix structure. These findings suggest that the loess layers' structural strength is associated with weaker pedogenic weathering occurring under cold and dry climatic conditions, whereas the paleosol layer exhibits a higher structural strength due to intense weathering during a warm and humid climate. Overall, this study establishes a link between paleoclimate and mechanical properties, using microstructure as a mediating factor, and provides a theoretical basis for tillage on the Loess Plateau.