Soil seed banks in plantations and adjacent natural dry Afromontane forests of central and southern Ethiopia
2002
Sendeta, F (Wondo Genet College of Forestry, Shashemene (Ethiopia)) | Teketay, D (Ethiopian Agricultural Research Organisation, Addis Abeba (Ethiopia)))
The soil seed bank was investigated in plantation stands and adjacent natural forests at Menagesha-Suba and Munessa-Shashemene forest sites in central and southern Ethiopia, respectively. The total numbers of species identified in the 0-9 cm soil layer were 58 at Menagesha-Suba and 52 at Munessa-Shashemene with the corresponding soil seed bank densities ranging between 27,200 and 82, 600 and 4,500 and 36,900 seeds m(-2), respectively. Herbs dominated both in the number of species and densities of seeds while the contribution of woody species was generally low. The horizontal distribution of seeds in the soil exhibited considerable variation at both sites. However, the overall vertical distribution of seeds in the soil was similar in all stands with the highest densities occurring in the upper three centimeters of soil with gradually decreasing densities with increasing depth. The similarity in species composition of the soil seed bank was generally low in stands both within and between the two sites. In general, the results provide further evidence that consolidate the conclusions of previous studies on soil seed banks in Ethiopia. The dry Afromontane region, in which the two study sites are located, can be characterized as possessing large numbers of buried seeds of forbs, grasses and sedges. Only a few woody plants are represented, and these by few seeds, in the soil seed bank, suggesting that most woody plants rather use the seed rain, seedling banks or copping from stumps as alternative regeneration routes. These results imply that the herbaceous flora has a better chance of natural recovery in the event of disturbances owing to the diverse soil seed banks while the regeneration of woody species, particularly trees and shrubs, would be prevented by removal of mature individuals and their seedlings on the forest floor since most of them lack seed reserves in the soil. This, in turn, indicates that future existence of the woody flora characteristic of dry Afromontane areas in Ethiopia depends on the conservation and sustainable utilization of the few remnant natural forests.
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