Objective Cementing substances in soil represent the most active components and form the foundation and core of soil aggregate formation. The aims were to clarify the effects of alpine meadow degradation and restoration processes on soil cementing substances.

Method This study investigated the changes in soil aggregate stability and cementing substance content during grassland succession (from natural Kobresia patches → degraded bare patches → transitional weed patches → naturally restored Kobresia patches / artificially restored Gramineae meadow patches), and examined the influence of various cementing substances on aggregate stability.

Result ① In the surface soil layer (0 - 10 cm), the mean weight diameter, geometric mean diameter and the proportion of macroaggregates decreased initially and then increased along the degradation and restoration gradient (P < 0.05). Moreover, natural restoration significantly improved aggregate stability compared with artificial restoration (P < 0.05). In the subsurface layer (10 - 20 cm), these indicators did not change significantly during the grassland succession. ② After grassland degradation, both organic and inorganic cementing substances in surface soil decreased significantly (P < 0.05). Following restoration, the contents of complexed aluminum oxides, glomalin-related soil proteins, total organic carbon, and aggregate-associated organic carbon significantly increased (P < 0.05). Among them, natural restoration markedly enhanced the levels of various forms of iron and aluminum oxides (P < 0.05). No significant changes were observed in the subsurface layer during the succession. ③ Based on pearson correlation, redundancy analysis, and partial correlation analysis, free aluminum oxides and complexed aluminum oxides were identified as the key cementing substances influencing the stability of surface and subsurface soil aggregates, respectively.

Conclusion The results demonstrate that the restoration of degraded alpine meadows affects soil aggregate stability by altering the content of cementing substances, and that different restoration approaches influence distinct types of cementing substances.