2.1. Phytogeography of the country
2.2. Utilization patterns of forest species
2.3. Threats
The forest ecological zones are similar to those described by Harrison and Jackson (1958).
The desert (zone 1)
This zone embraces vast areas of northern Sudan, approximately 29% of Sudan total area. The annual rainfall is less than 75 mm and with red sandy soil. Woody vegetation is around the Nile banks and seasonal watercourses, mainly Acacia tortilis, Ziziphus spina-christi, Boscia senegalensis, and Cadaba farinosa. Towards the southern part of the desert, where increased rainfall permit, woody species like Indigofera bracteolata and Fagonia cretica are found scattered all over. Along the Nile bank the tree species present are Acacia nilotica, Faidherbia albida and Acacia seyal.
Semi-desert (zone 2)
This zone constitutes about 19.6% of the area of the country. Annual rainfall ranges from 75 mm in the north to 300 mm in the southern fringe. According to soil type, the vegetation is subdivided into:
Low rainfall woodland savannah (zones 3 and 4)
It covers 27.6 % of the country on clay and sandy soils with annual rainfall between 300 mm and 800 mm. It is subdivided into two zones according to soil type:
High rainfall woodland savannah (zone 5)
The main species of this zone are: Khaya senegalensis, Combretum hartmannianum, Parkia africana, Daniellia oliveri, Isoberbinia doka and Anogeissus leiocarpus.
Special forest Types (zone 6)
These forest types lie within the low rainfall savannah or even the semi-desert areas. They are mainly around the rivers and seasonal watercourses. The most important species is Acacia nilotica, Ziziphus spina-christi, Faidherbia albida, Hyphaene thebaica, Borassus aethiopum, and Oxytenanthera abyssinica.
Montane forests (zone 7)
Four important mountain masses occur in the Sudan, which are the Red sea Hills in the east, Jebel Marra in the west, and Imatong and Didinga mountains in the south. They occupy less than 1% of the country, with minor and introduced species.
The forest tree species in Sudan have economical, ecological, and recreational values. The woody products from the forestry sector are sawn timber, round poles, and fuelwood. The Forest Product Consumption Survey (1995) showed that the total annual consumption of wood in Sudan was 15.77 million m3. Fuelwood share was 87.5%, as the most important direct benefit from the forest. Ecologically forest tree species stabilize sand dunes in the fragile system in the semi-desert region, ameliorate soil through nitrogen fixation, and provide natural ecosystems for wildlife and conservation of biodiversity.
Fuel wood
Fuelwood contributes 78% of the energy balance of Sudan; the rest are 8% oil, 8% generated electricity and 6% agricultural residues. However, the 8% of the oil balance consume all the export returns of the Sudan. Rural inhabitants use most of the tree species in the low rainfall savannah for fuelwood (wood and charcoal). Removal of dead trees and branches is permitted for people living around forests. Forest authorities direct the commercial logging of mostly Acacia nilotica and Acacia seyal for firewood and charcoal for supply to the cities.. This is mostly from thinning and branches of Acacia nilotica in the reserved riverine forests, and clearing of Acacia seyal and other acacias from areas allocated for agriculture.
Saw timber
The main wood products are building poles, sawn timber in the form of railway sleepers, construction and joinery elements. The study showed that the household sector uses 89.4% of the total wood produced while industrial, commercial and service use amount for 10.6%.
Sawn timber is mainly from Acacia nilotica and other species of the high rainfall savannah woodland zone like: Isoberlinia doka, Khaya grandifoliola, Milicia excelsa, Khaya senegalensis, Olea hochstetteri, Afzelia africana, Daniellia oliveri, Sclerocarya birrea, Podocarpus milanjianus and Acacia nilotica.
Non-woody products
Non-woody products contribute significantly to Sudan exports (19.35% of the total exports). Other forest products of importance to rural communities are honey, fruit, fibers, food, fodder, medicinal materials, dyes and as tannin material.
Gum arabic from Acacia senegal and other acacias generate income for farmers and contribute significantly to Sudan exports. Badi (1993) provides an exhaustive list of about 100 species bearing non-woody products used as food, oil, fodder, gum, fibre, medicine, and tannin agents. Policies are now towards reducing the consumption of wood as an energy source and increase their use as sawn timber for furniture. Research is encouraged to identify uses of woody and non-woody products for high commercial values.
The Sudan forest tree vegetation cover was estimated as 40% in 1901 of the total area, 34-36% in 1958 (Harrison and Jackson 1958), and decreased to 19% in 1990 as estimated by the FAO. It decreased further to 13.7% according to the recent surveys (Abdelnour and Abelmagid, 1997).
Man has been the most powerful and persistent factor that caused the deforestation and disturbance of Sudan natural ecosystems. The main human activities that are threatening the tree species and endangering some of them are unregulated cutting for timber and fuelwood, clearing of forestland for agriculture, overgrazing of livestock, burning and civil wars.
About 80 per cent of Sudan’s population derives its living from crop farming or grazing. Approximately 5 percent of the country’s land area is used for arable cultivation; large areas are used for seasonal grazing. The chief food crops include sorghum (durra), millet, wheat, rice, sesame, cassava, potatoes, beans, bananas, sugar cane, and groundnuts (peanuts). Cotton is Sudan’s leading cash crop; it is produced in large amounts in the Gezira region between the Blue and White Niles. The livestock population in 1995 included about 35 million chickens, 23 million sheep, 22 million cattle, 16.5 million goats, and 2.9 million camels. Livestock production is carried out mainly through nomadic pastoralism using traditional practices (Libanis, 1998). During the 1970s large-scale mechanized production of sorghum was introduced in eastern Sudan, in the area between the Blue Nile and Atbara rivers. Production increased hugely, particularly in 1994, enabling Sudan for a while to become an exporter of the grain, but at the cost of soil erosion, and increased desertification (Libanis, 1998).
The demand for wood, mainly for fuelwood, is high in the north beyond the allowable cut. The situation in the north is becoming more critical due to extensive clearing for large scale mechanized farming operation, and overgrazing. If current rate of clearing for wood and agriculture continues, there will be no forest in the low savannah regions shortly.
The civil war in the south is posing a serious threat to forest resources. Apart from that the non-human factors threatening the forest tree species and consequently the genetic resources are drought, natural tires, and insects. In addition, the drought of the 1980’s affected tree spp seriously in the low rainfall savannah areas and arid zones.
