Spatial correlation network characteristics and influencing factors of urban ecological vulnerability in the Yellow River Basin, China.

Against the backdrop of arid and semi-arid climates, plantation degradation in the Three-North region of China has emerged as a critical constraint on regional ecosystem stability and the sustained provision of ecosystem services. We synthesized the major manifestations and plantation degradation in the Three-North region. Plantation degradation is commonly characterized by tree physiological dysfunction, accompanied by growth decline at indivi-dual and stand scales, stand structural instability, and a decline in ecosystem functions. From an integrated ecological and tree physiological perspective, we highlighted how key ecological drivers, including water stress, nutrient limitation, and tree species-site mismatch under drought stress, could induce hydraulic failure, carbon starvation, and imbalance in water-carbon coupling, thereby driving the transition of plantations from physiological decline to structural and functional degradation. Moreover, we emphasized that tree species with different water-use strategies exhibited distinct degradation pathways and risk profiles under drought stress, which were jointly regulated by hydraulic safety margins and carbon balance constraints. Despite growing attention, substantial gaps remained in identifying dominant driving factors, quantifying key physiological thresholds, and elucidating cross-scale coupling processes. Future studies should integrate multi-scale indicators, such as water use efficiency, to develop species- and region-specific diagnostic and early-warning frameworks for plantation degradation.