Drivers of vegetation and soil seed bank dynamics in the Bale mountains of southeastern Ethiopia: implications for ecosystem restoration

Abstract

Abstract Mountains are highly vulnerable to climate change, influencing species distributions, soil seed bank dynamics, and ecosystem resilience. This study examined relationships between aboveground vegetation and soil seed banks across five altitudinal ranges (2500–2700 m, 2800–3100 m, 3200–3500 m, 3600–3900 m, and >4000 m) in the Bale Mountains, encompassing Dry Afromontane, Ericaceous, and Afroalpine vegetation types. At each range, five 10 × 10 m plots were established to sample soil at three depths (0–10, 10–20, and 20–30 cm) and record floristic composition. Soil seed bank germination was assessed under greenhouse conditions, and soil nutrients were analyzed in the laboratory. Species composition differences were evaluated using Bray–Curtis dissimilarity, while the effects of altitude and soil nutrients were tested using Adonis2 and canonical correspondence analysis (CCA). Difference in species richness and seedling density among vegetation types and soil depths were analyzed using ANOVA. Aboveground vegetation and the soil seed bank showed strong compositional dissimilarity (Bray–Curtis = 0.91). Soil nutrients, including organic matter, soil organic carbon, available phosphorus, available potassium, and total nitrogen, significantly influenced species composition (P < 0.05). Soil seed bank richness declined with depth, reaching its lowest at 20–30 cm (6.48 ± 3.15). Above ground species richness varied significantly with altitude, with the lowest values above 4000 m (6.8 ± 2.40). Soil seed bank richness peaked at 3200–3500 m and decreased toward both lower and higher elevations. Overall, altitude and soil depth strongly shaped species composition and seed persistence, highlighting mid- altitudinal habitats as key reservoirs of plant diversity and ecosystem resilience.