SOME BIOLOGICAL AND ECOLOGICAL STUDIES ON ACACIA DREPANOLOBIUM SJÖSTEDT IN BORANA, OROMIYA REGIONAL STATE, ETHIOPIA

Abstract

Studies on A. drepanolobium Sjöstedt, including effect of environmental factor, seed production, seed dispersal, soil seed bank, percent seed germination and coppicing capacity were conducted in Borana, Ethiopia. Although there were significant differences on soil properties among sites, pH and EC were within the normal range, and soils were rich in clay. Seed production per plant was 2417 ± 23 (X±SE), and very few trees bore seeds per plot. Seeds were found to disperse mainly by wind and water. Few seeds (<10 seeds/m²) were found in the litter layer and none in the mineral layer. Statistically significant differences were found in percent germination [F_{(5, 17)}, P < 0.05]. Fast rate and higher percent germination were achieved by scarification whereas dry (90°C) and moist heat treatments (98°C) resulted in mold outgrowths. Tukey’s HSD indicated that moist heat treatments did not improve the percentage germination. High percent and fast germination of A. drepanolobium in the control suggest the absence of marked seed dormancy. Stumping treatments did not show any significant differences but the coppice number and height tend to increase to the surface. Although Borana rangeland is home to A. drepanolobium, the species is becoming an aggressive invader. The seed sensitivity to high heat and the death of coppices by stumping at heights > 50 cm indicate that the species can be managed by periodic burning and cutting the tree for charcoal/firewood purposes. Further, awareness creation on the impacts of overgrazing and bottomland cultivation could also assist in the management of the species. Therefore, we recommend an integrated approach in the management of A. drepanolobium that should involve the local community.