Restoration interventions enhance plant species diversity and composition in the humid tropical highlands of Ethiopia.

Land degradation in the Ethiopian highlands poses a significant threat to biodiversity and ecosystem services. While large-scale afforestation, reforestation, and natural resource management interventions have been instigated, empirical evidence on their ecological effects remains inadequate. This study aims to examine vegetation diversity and plant community composition patterns associated with land restoration interventions across three agro-ecological zones in the humid tropical highlands of Ethiopia. Vegetation data were systematically collected from 672 plots established across 56 watersheds, using nested plot designs for trees (20 m × 20 m), shrubs (5 m × 5 m), and herbs (1 m × 1 m). The study employed a watershed-level paired treatment-control sampling design in which nine treatment plots and three adjacent control plots were established across three landscape positions per watershed. Results revealed a total of 160 plant species belonging to 121 genera and 74 families. Treated watersheds exhibited significantly higher mean species richness and Shannon diversity, while untreated control sites showed higher Simpson diversity in the tepid sub-moist highlands. Community-level analysis identified five major plant community types, with Community 4 showing relatively advanced ecological recovery patterns, while Community 3 was primarily characterized by plantation and agroforestry-associated species assemblages. Correlation analysis revealed strong positive associations between species richness and Shannon diversity and major restoration measures, including area closures, agroforestry, soil bunds, and stone bunds (r > 0.90, p < 0.001). In contrast, Simpson diversity showed negative associations with most restoration interventions, reflecting reduced species dominance under restored conditions. Overall, the findings indicate that integrated physical and biological restoration interventions are associated with improved floristic diversity and vegetation recovery patterns across the Ethiopian highlands. Site-specific and context-adapted restoration strategies are therefore essential for sustaining biodiversity conservation and enhancing ecosystem resilience.