Woody composition, diversity, and soil properties in exclosures of semi-arid central Tigray, Ethiopia

Globally, deforestation remains a major driver of land degradation, despite recent reductions in forest loss. In Ethiopia, exclosures are implemented as nature-based solutions to restore degraded landscapes and promote vegetation recovery. This study evaluates woody floristic composition, species diversity, and soil properties in 15- and 32-year-old exclosures, comparing them to nearby rangelands where livestock graze year-round. Using a systematic sampling method, 36 plots (400 m2) were established across elevation gradients to survey woody vegetation and collect soil samples. Nonmetric Multidimensional Scaling (NMDS) analysis examined woody community composition, and t-tests compared soil and vegetation properties between exclosures and rangelands. Forty-two woody species from 25 families were identified, with Dodonaea angustifolia, Becium grandiflorum, and Euclea racemosa being the most common. Both exclosures showed significantly higher species richness and Shannon diversity than rangelands (p < 0.01). The 32-year-old exclosure had greater tree abundance and species evenness compared to the 15-year-old exclosure. However, no significant differences in soil properties, including electrical conductivity, organic carbon, nitrogen, and pH, were found between exclosures and rangelands. The 15-year-old exclosure did show significantly higher cation exchange capacity (CEC) compared to the rangeland (p < 0.05). Correlation analysis revealed a strong positive relationship between species diversity and exclosure age, while soil properties remained largely unchanged, except for CEC. The study highlights exclosures as an effective nature-based solution for enhancing species richness and biodiversity, supporting their use in land restoration. However, the lack of significant soil improvement suggests that vegetation recovery does not always lead to immediate soil enhancement, underscoring the need for long-term monitoring to understand the ecological impacts of exclosures.