Indigenous Tree Species Diversity Under Exotic Plantations in Qimbaba Forest, North West Ethiopia

Abstract

This study was carried out in Qimbaba forest, northwest of Ethiopia to determine woody species diversity, regeneration capacity and soil seed bank in Eucalyptus plantation forest and adjacent natural forest. A total of 40 circular sample plots of 314 m² were established along a transect line at every 200 m between them. Transects were laid in east–west directions at 200 m distance from each other. Soil seed bank analysis was done from soil samples collected in each of the 40 plots (160 samples) to examine the similarity between the soil seed flora and aboveground vegetation. A total of 71 woody plant species (33 in Eucalyptus Plantation) and (63 in Natural Forest) were determined with the density ranging between 404 to 635 per ha in the plantation and natural forest, respectively. The population structure showed an inverted J-shape in both forests. The basal area were 4.9 m²/ha and 24.5 m²/ha for plantation and the adjacent natural forest respectively. The regeneration status in the Eucalyptus plantation was 699 seedlings and 344 saplings/ha while the natural forest had 1117 seedlings and 390 saplings/ha. On the other hand, the species richness of regenerated trees in the plantation and natural forest were 21 and 38, respectively. A total of 14 plant species representing 11 families were recovered from the soil seed bank, 12 (in 10 families) species in the natural forest and 7 of them were in the eucalyptus plantation forest (5 families). Soil seed bank (SSB) was not similar in the two forests with Sorenson’s similarity values of 0.208. There were 11,022 seeds/m² (natural forest) and 10,667 seeds/m² (Eucalyptus plantation forest) in the SSB.

Keywords: Florstic diversity, Eucalyptus, Natural forest, Soil seed bank, Fostering effect