Study of Soil Seed Banks in Ex-closures for Restoration of Degraded Lands in the Central Rift Valley of Ethiopia

Soil seed banks (SSB) can be important components in the process of rehabilitating degraded lands. Thus, this study was aimed to evaluate the role of SSB to the restoration of degraded lands in six, fifteen and twenty-five year’s ex-closures and adjacent degraded open grazing land (DOGL). Totally, 160 samples of SSB from four soil layers (litter, 0–3 cm, 3–6 cm & 6–9 cm), four sites and ten in a composite of 5 (15 × 15 cm) were collected and tested for seed viability through seed extraction and seedling emergence methods. Species richness and diversity showed a significant difference between the SSB of the ex-closures and DOGL (P = 0.0148 and P = 0.0218 respectively). Seed densities also showed significant differences between the vertical layers of the soils in the ex-closures and DOGL (P = 0.0112) and the interaction effect of the land use type and the vertical soil layers (P = 0.0174). Ex-closures and DOGL scored highest seed densities in their litter and bottom layers of the soils respectively. Most of the woody species in the SSB of older ex-closures were represented in the aboveground flora. Thus, this study has verified that SSB has played a vital role in the restoration of woody species in degraded land through ex-closure practices.