Woody species diversity, structure and regeneration status of Omo National Park, Southern Ethiopia

Abstract

Ethiopia's rich ecological landscapes, including its protected areas, are increasingly threatened by deforestation, agricultural encroachment, overgrazing, and climate variability. This study assessed the woody species composition, structure, and regeneration status of Omo National Park, located in southwestern Ethiopia. A total of 97 main plots (20 m × 20 m) for mature trees, 97 subplots (5 m × 5 m) for saplings, and 388 microplots (1 m × 1 m) for seedlings were systematically established. Woody species with a diameter at breast height (DBH) ≥ 2.5 cm and height ≥ 2.5 m were measured. In total, 72 woody species belonging to 51 families and 28 genera were recorded, comprising 39.5% trees, 57.9% shrubs, 1.6% tree/shrub forms, and 0.21% climbers from 950 individual plants. Fabaceae (10 spp.) and Combretaceae (7 spp.) were the most species-rich families. The park exhibited a high Shannon diversity index (3.34) and evenness (0.74), with a mature woody plant density of 244.8 individuals ha⁻¹ and a total basal area of 17.76 m² ha⁻¹. Species frequency declined with increasing DBH and height classes. Seedling and sapling densities were 450 and 411.6 individuals ha⁻¹, respectively, indicating good overall regeneration status. The study highlights the need for targeted monitoring and management of dominant and potentially invasive species to ensure the park's ecological sustainability.