Abstract
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.
Highlights
Government and non-government organizations have been promoted and started rehabilitation practices on the degraded lands of the country using a set of passive rehabilitation measures ex-closures were dominantly practiced[2,4,5]
A total of 16 woody species in 12 families were recovered from the litter and the top nine centimetres of the soil samples collected from all the ex-closures and degraded open grazing land (DOGL) (Supplementary Table S1)
The 10% of the woody species in the soil seed banks which had not denoted in the aboveground flora of twenty-five years ex-closure indicating that some seeds of woody species in the soil seed banks could stay more than twenty-five years as persistent until specific environmental requirements of woody species germinations are changed
Summary
Government and non-government organizations have been promoted and started rehabilitation practices on the degraded lands of the country using a set of passive rehabilitation measures ex-closures were dominantly practiced[2,4,5]. In the passive restoration of degraded lands, the presence of viable soil seed banks and changes in environmental conditions such as moisture, light regime, and temperature fluctuations are very essential which may bring about the germination of dormant seeds that have remained viable in the soil for several years[9]. This implied that species overcome periods of unfavourable weather conditions by building up large seed stock in the soil, which is known as “soil seed banks”. The emphasis was to: (1) Determine the composition, density, diversity and richness of woody species in the soil seed banks of six, fifteen, twenty-five years ex-closures and DOGL, (2) Investigate the soil seed bank distribution of woody species in the vertical layers of the soils in the six, fifteen, twenty-five years ex-closures and DOGL, (3) Examine and compare the similarities between woody species richness and diversity in the soil seed banks and their respective aboveground standing woody species in the six, fifteen, twenty-five years ex-closures and DOGL thereby to determine the role of soil seed banks to the restoration of woody species in the ex-closures
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