The use of site index for monitoring site quality and productivity of the Sunt plantation in the Blue Nile Case Study: Riverain Forest along the Blue Nile Lembwa Forest

The Forests are rapidly dwindling and ground vegetation has disappeared from extensive areas, creating various environmental hazards, forest products scarcity and land productivity decline. These results are largely attributed to the management approaches currently adopted in Sudan, which are criticized as being inefficient and unsustainable. Riverain forests lie long both banks of the Blue Nile as detached area, have from a very unique forest ecosystem. Acacia nilotica (Sunt) has been found the most valuable timber producing species. Since the establishment of the plantations in 1935, the species was managed on thirty year's to approach normal structure and attain sustainable production. They were for some times managed for sustained yield throughout the first thirty years rotation (1935-1964), presently the forests are described as declining in productivity. A difference in growth trends and production potentials exists between two site quality classes. Stands in both quality classes are at present managed with similar objectives and on the same rotation. But they produce timber of different quality and size. The main objective of the present study is to evaluate the productivity of the site Sunt plantation and the possibility for their management on sustainable production basis. The area / age distribution over the first rotation (1935-1964) area related to total area, indicates a stable and balanced structure of organized distribution of Acacia nilotica stands in space (area) and time (age). This structure is an indication of a sustainable form of management. Being grouped in five years age classes, the difference between groups in area is very small from the average (11520/6 =1920 feddan / 5 years group), The second thirty years rotation (1965-1994) indicates a wide variation between the actual areas within 5-years groups and the expected average of (1920-2000) feddan. Similar trends or area / age distribution were detected for individual forests. In Lembwa forest the area / age structure in a series of one year age groups was developed for 13 compartments in 1987. The thirteen compartments were delineated into three units of one year age-group in 2004. All the compartments in Lembwa forest were inventories in 1987 and in 2004 for site index values and quality class assessment, using top height against age. The compartments indicated a change Q.C.I during the 1987 to Q.C.II in the 2004 inventory as a result of failure to control felling or top VII height trees. This was verified by measurement of the diameters of large stumps and projection of d b h estimations to height estimated. The estimated height resulted in adjustment of compartments Quality class to class