Ecological Status Index and Sustainability-Oriented Regional Assessment of Redbed Ecosystems in China

Redbed ecosystems are characterized by strong spatial heterogeneity and are vulnerable to water limitation, soil erosion, and land-use disturbance, creating challenges for sustainable ecosystem management across China. A single ecological indicator cannot adequately represent the multidimensional conditions of redbed regions. This study developed a sustainability-oriented regional assessment framework by integrating lithology, geomorphology, climate, soil, and vegetation and constructing an Ecological Status Index (ESI) using entropy-weighted linear aggregation. Soil properties, the kernel normalized difference vegetation index (KNDVI), and vegetation types were analyzed to characterize regional ecological differentiation. The results show that soil clay content is an important factor regulating soil water-holding capacity, whereas greater soil thickness does not necessarily correspond to higher soil organic carbon content. KNDVI remained relatively high in ferrallitic and leached soils, while values in arid, desert, saline–alkali, and alpine soils were generally below 0.1. KNDVI and precipitation received the largest individual weights, accounting for 19.10% and 17.55%, respectively. Regional ESI values ranged from 0.1589 to 0.8164, with the highest value in Region 11 and the lowest in Region 2. Regions 10-2 and 9-2 also ranked highly, whereas Regions 1 and 3 exhibited low values. The regional assessment revealed variation within the four broad ecosystem classes and distinguished alpine constraints from arid limitations. By linking ecological regionalization with quantitative status assessment, the proposed framework provides a basis for sustainable land management, soil and water conservation, and site-specific ecological restoration in redbed regions.