The effect of utilization on seed bank and vegetation dynamics of indigenous plant species including selected wild foods in Rawashda forest in eastern Sudan [Sudan]

The study covered the ecological process as a result of past and present use of nomads on range plants and trees, in the Rawashda forest reserve in eastern Sudan, for the seasons 1992 and 1993, it also covered the significance of different utilization levels on the forest environment, the potential of forest productivity through seed bank and persistency studies in 1993 and 1994, the biological productivity of selected range plants that have wild food importance, beside socio-economical studies of nomadic tribes herding in the forest area. Vegetation studies showed, low percentage of monocotyledons to dictyledons (4.7 in 1992, and 6.6 in 1993), related to the total hits on plants along the transects. There was total increase in the numbers of less preferred species and a decrease in the numbers of preferred ones. Preferred species showed some dominance early in the season, at the time of maximum vegetative growth, while the less preferred ones showed that later at the time of seed setting which may give them more chance to contribute to the seed bank in the forest. The preferred species showed high diversity early in the season (14 kinds in 1992, and 11 kinds in 1993) but decreased sharply late at the time of seed setting to 5 and 6 kinds respectively, showing less stability along the season, while the less preferred one seem to be more stable, since they started with 8 kinds in both seasons but ended with 6 and 8 kinds for the two seasons receptively. Carrying capacity studies showed that the forest was not only severely utilized at the proper time of use, but also at improper one, this was found true for both seasons 1992 and 1993. There were significant difference along the different utilization levels (Protected, normally grazed, and destroyed), in term of total biomass production for 5 harvesting dates in 1993 rainy season, and for the species Justica flava at the time of maximum vegetative growth, as a result of selective grazing. Seed and fruits production of Sesabania spp showed significant along the uttilization levels. Protected areas dominated by species like Dinebra, Commelina, normally grazed areas dominated by less preferred species like Leonotis africana. Solanum spp which is poor range plant seemed to dominate degraded areas in the forest. The browsing utilization on Acacia seyal in 1992 was more early in the season than late, with a difference of 5.8, and more on variety seyal than fistula. In 1993 it was also more early in the season than late, with values of 32.7 in October and 32 in December for seyal, 46.6 in October, and 40.68 in December for fistula. The biological productivity studies showed that C. olitorius, C. fasicularis, Brachaiaria obtusiflora, and Dactyloctenium aegyptium showed different days to emergence in 1992 and 1993, but the germination of C. olitorius, and D. aegyptium was more responsive to seasonalvariation than the other two species. All the species showed less days to flowering and seed setting when grown late in 1993. D. aegyptium tried to shorten its life cycle when grown late in the season, while the opposite responce shown by C. fasicularis. C. fasicularis showed best production of dry matter in September 1993 compared to July, but with a decrease of 24 of seed production compared to 1992. In July 1992 it showed the highest seed production for the two seed rates. Olitorius produced in September 1993 8 times the a mount of seed production as in September 1992, this species showed different response to the seed rate at early and late sowing in 1993.B. obtusiflora showed the best production of seed and dry matter in 1993 compared to 1992, but the different seed rate didn't show difference in seed production more than 17 in September. Seed bank studies showed that, the total numbers of seeds detected in the seed bank were very little compared to the forest flora in term of quantity and quality. Species composition in the seed bank was also varied between the treatments. Seed persistency experiment showed that, although no significant differecnes were detected, more seeds were lost from the surface than 10 cm. depth, and this varied between species in different groups. Normads socio-economical studies proved that, in eastern Sudan they were more familiar with C. olitorius and H trionum as wild food and range plants, they use their leaves and fruits, use them dry and fresh, but C. olitorius and H trionum. are more common than the other species. less families were familiar with D. aegytium and B. obtusiflora as wild food plants, and it used they use their seeds, D. aegyptium die soon after the rainy season, while B. obtusiflora seemed to grow better in more wetter areas. The time of nomads entrance, exit, re-exit, and how long they stay in the forest was dictated by the rainfall and environmental condition in each season. All nomads herd to the north at the onset of the rainy season. They are more reluctant to measures like reducing numbers of live stock, fencing or allotting areas per tribe as a way of range improvement in forest.