| dc.description.abstract | Vast areas of forests have been degraded in Ghana. The degraded areas are generally
invaded by Chromolaena odorata, a strong competing species for trees. Planting is the
major primary means that is currently used to restore these areas back to forests.
However, natural regeneration or human-assisted natural regeneration may provide an
alternative way to regenerate these areas. To evaluate the potential of this alternative, the
density and species composition of tree seedlings under the canopy of Chromolaena
odorata and the seeds of both trees and Chromolaena odorata in a degraded area were
estimated. The response of tree seedlings to the removal of Chromolaena odorata was
also examined. One hundred and eight plots were established 20 m apart for assessing
the tree seedlings. Chromolaena odorata was removed from SO % of the plots to release
tree seedlings and left the other half intact. Seedling height, the number of leaves per
seedling, and seedling mortality were assessed in both released and unreleased plots
immediately after the release treatment (June 1998) and again three months later
(September 1998). Smaller plots (0.2S m2) next to half of the seedling plots were used to
sample the soil seed bank. The soil samples were taken from two different depths and
germinated in a germination house. Fifty five species of tree seedlings and seven species
of tree seeds were found at the site. There were 11,780 seedlings ha-1 and the seedlings
were well distributed in the degraded area. The density of tree seeds (46,000 seeds ha-1)
was 3.8 times higher than tree seedlings, but the species composition o f tree seedlings
was 7.8 times higher than the species composition of seeds. The spatial distribution of
tree seedlings was more even than that of tree seeds. The tree seed density did not vary
significantly with soil depth but the seed density of Chromolaena odorata (73.89 million
seeds ha*1) decreased with increasing depth from the surface. There were 1,606 times
more Chromolaena odorata seeds in the soil seed bank than tree seeds. Tree seedlings
responded positively to the removal of Chromolaena odorata. The height increment and
the increase in number of leaves per seedling were three times greater in released
seedlings than the unreleased ones three months after the release treatment. Sixty four
percent o f the species suffered various levels of mortality in the unreleased plots, but all
the seedlings of all the species survived in the released plots. The results suggest that
there are enough tree seeds and tree seedlings to restore the degraded area back to forest.
However, tree seedlings will have to be released from the competition of Chromolaena
odorata. | |
