Synergistic Degradation Relationship Between Root–Soil Properties and the Evolution of Mattic Epipedon Cracks in Alpine Meadows

ABSTRACT During the degradation process of alpine meadows, the vegetation–root–soil system has degraded synergistically, and the composition and structure of mattic epipedons have altered, resulting in gradual thickening accompanied by the emergence of cracks and a qualitative shift in the degradation state. Clarifying root–soil–crack interactions during this process remains challenging. In this study, root–soil properties and crack evolution were investigated using redundancy analysis (RDA), and root reinforcement effects were quantified through the Wu–Waldron model (WWM). The results revealed that degradation significantly affected soil structure, root architecture, and crack morphology ( p < 0.05). Anthropogenic disturbances drove a compositional shift in plant communities from fine‐rooted graminoids and sedges with high tensile strength to coarse‐rooted forbs with lower tensile strength. This transition reduced the soil reinforcement capacity by about 44%, generating stress‐weakened zones within the mattic epipedon that initiated surface cracking. RDA revealed root length density as the primary driver regulating crack propagation and morphological evolution. Furthermore, crack development exacerbates soil and water erosion, impedes vegetation and root growth, and further destabilizes the turf layer. Exacerbated by external environmental stresses, specifically wetting‐drying and freeze–thaw cycles, crack expansion accelerates, triggering a self‐reinforcing cycle of degradation. Crucially, we identified a critical threshold: once the fractal dimension of the crack network reached about 1.58, the alpine meadow ecosystem underwent irreversible degradation. This study elucidated the coupled interactions between root–soil properties and crack development under degraded conditions, offered diagnostic indicators for a more intuitive assessment of meadow degradation, and provided a theoretical basis for understanding the development, progression, and ecological regulation of mattic epipedon cracks in alpine meadow ecosystems.