Effects of fire on soil seed bank, vegetation cover and some soil properties in ElNour forest at Blue Nile State

This study was carried out in ElNour Forest in the Blue Nile State. The selected site was dominated by Acacia trees (A. seyal. A. senegal). These trees were cleared from the site to determine trees and dominant grasses (Brachairai obtusiflora. Cymbobogon nervatus) soil seed banks and it's power to regenerate the site with this soil seed banks. The site was treated with three levels of intensity (Light. Moderate and Severe) fire to determine the effect of fire on natural regeneration of the tree through its effects on soil seed banks and soil properties, which influence the natural regeneration. Fire treatment was repeated for three successive seasons. The results showed that fire had no effect on the soil seed bank of A. seyal, A. senegal and C. nervatus but B. obtusiflora soil seed bank was increased. The soil seed banks of A. seyal, B obtusiflora and C. nervatus decreased with seasons, but seasons have no effects on A. senegal soil seed bank. For the grasses soil seed bank most of the seeds were in the top soil 2 cm rather than 5 and 10 cm. The fire has no effects on vegetation cover biodiversity because it has no effects on vegetation cover richness or density accordingly the plants in the site were classified as fire resistant species. The equitability of the species in vegetation cover was not affected by fire. The equitability of A. seyal was stable through the seasons but it decreased in the case of grasses. Fire was found to have no effect on soil nitrogen, phosphorus, organic carbon, pH and soil moisture content, seasons also have no effect on soil characters except soil pH and phosphorus, which decreased with the seasons. It was concluded from this study that grass fire was not an important factor that affect natural regeneration of A. seyal forests in the contrary of what is believed by the forest management authorities for regeneration of A. seyal forests. A kind of plant succession was observed in the site which started after tree clearance, where the grasses dominated the site for 2-3 years and then decreased with seasons to allow Acacia seedlings to colonize in the site. This succession was found to coincide with Phosphorus depletion and decrease in pH and this may be the main cause for such kind of succession that the grasses exploited soil P for 2 seasons when the grasses fail to produce seeds at low content the tree seedling appear. It is recommended to use soil seed bank rather than replanting for reforestation of the A. seyal forests. This method is cheaper and may creates rich biodiversity