Uganda covers a land area of 196 840 km2 between latitudes 1°30' south and 4° north and between longitudes 29°30' and 35° east. In addition 41 500 km2 of the country area are open water and swamp.
Physically, the country consists of a plateau generally between 1 200 and 1 500 m dissected by numerous streams. In the west, this plateau is interrupted by an escarpment forming the lakes Edward and Albert, with the uptrust of the Ruwenzori mountains (5 110 m) in the centre between the lakes. In the extreme north the plateau extends across the Nile into the district of West Nile. The south-west is very hilly and higher than the rest of the country. In the east, along the border with Kenya, three high mountains dominate: Elgon (4 321 m), Kadam (3 068 m) and Moroto (3 083 m).
The Nile divides the country in two parts, flowing from Lake Victoria at Jinja through Lake Kyoga to the northern tip of Lake Albert, and then north to the Sudan. A significant proportion of the southern part of Uganda contains swamps.
The climate is tropical, with 1 000 mm or more rainfall over most of the country. In the extreme northeast, in Karamoja, exists a small zone with less than 500 mm of rainfall (2).
The population is estimated for 1980 at 13.2 million inhabitants, with an annual growth rate of about 3.1%.
1. Present situation
1.1 Natural woody vegetation
1.1.1 Description of the vegetation types
The following description of the woody vegetation of Uganda is based on (7).
Closed broadleaved forests (NHC)
a) Lowland forest (below 2 000 m)
Two major forest areas remain in Uganda: the forests around lake Victoria and those of the Western Rift Escarpment.
- The forests of the lake Victoria belt start from Jinja, where the Nile leaves the lake, and continues westwards along the northern shore of the lake, down the western shore and towards Tanzania (east of the Nile very little is left of the dense forest, which covered most probably large areas in former times). These forests cover also some of the islands in the lake. The forests lie around 1 200 m and extend inland for 50–60 km. Generally the hilltops are covered by a short grass vegetation, the hillsides by a mixture of cultivated areas and elephant grass thickets (natural fallow) and in the valleys by forests and swamps. Most of them are small, but some cover up to 20 000 ha (between Jinja and Kampala). Although there are many different communities in the climax forests in the lake Victoria belt, there is a tendency towards dominance by the genera Celtis, Chrysophyllum, Aningeria, Piptadeniastrum with among lesser important species Morus, Holoptelea, Antiaris and Alstonia. In the understorey occur Trichilia, Teclea, Lychnodiscus, Lasiodiscus and Acalypha. The species which usually characterize the succession of secondary forests are: Albizia, Antiaris, Blighia, Canarium schweinfurthii, Celtis africana, C. durandii, Entandrophragma, Fagara, Lovoa, Majidea and Pycnanthus.
- The lowland forests in the Western Rift Escarpment form a belt of large forests between 500 to 1 650 m.a.s.l. The rainfall ranges here from 1 250 to 1 625 mm. The forest areas are separated by farmlands and various types of “post-cultivation” vegetation, mainly elephant grass thicket and Hyparrhenia grassland. Formerly, many of the existing forests must have been connected with each other and with the Ituri forest in Zaire. These changes have occurred, due partly to climatic variations as it seems unlikely that human activities alone would account for them.
These forests, unlike the lake Victoria belt forests, have a tendency to monospecific dominance. After the initial colonizing forest, a mixed forest appears with Alstonia congensis, Trichilia prieuriana, Khaya anthotheca, Celtis mildbraedii, Cynometra alexandri among others; its composition varies much from place to place. The climax forest that develops afterwards depends on altitude: from 1 000 to 1 200 m Cynometra alexandri is highly dominant (Uganda ironwood); the understorey is sometimes dominated by Lasiodiscus mildbraedii and sometimes by Celtis spp. and Strychnos mitis. Very large trees, other than Cynometra occur, such as Khaya and Entandrophragma. Patches of characteristic colonising species (e.g. Maesopsis), mature alongside climax canopy species in a mosaic pattern, in the spaces left by the fall of large trees. Another type of climax community is the Parinari forest, consisting of almost pure stands of Parinari excelsa, associated in the understorey with Carapa grandiflora. Other understorey species are: Craterispermum laurinum, Trichilia prieuriana and Pleiocarpa pycnantha.
Large patches of lowland bamboo (Oxytenanthera abyssinica) are found in the Acholi and West Nile districts. They are 4–9 m high, not very dense and have a sparse ground layer.
b) Upland forests (above 2 000 m)
The upland forests are usually separated from the lowland or medium altitude forests by grassland and cultivation areas. The latter reach in the Western Escarpment a maximum altitude of about 1 650 m, and from here on, up to about 2 100 m, much of the original forest has been removed. Only in the south-west exists a continuous forest cover from 1 500 m up to 2 400 m called “the impenetrable forest”. The upland forests in Uganda are considered to extend to about 3 150 m. Their composition varies from mountain to mountain, but four principal communities are found: Juniperus forest, Chrysophyllum forest, bamboo thicket and Hagenia-Rapanea woodland. According to the elevation three zones can be distinguished (lower, intermediate and upper) and in each of them a wetter, intermediate and a drier type.
- In the wetter lower zone from 1 525 to 2 440 m, occurs Aningeria adolfi-friederici in association with Alangium chinense, Albizia gummifera, Allophylus abyssinicus, Casearia battiscombei, Tabernaemontana sp., Croton macrostachyus, Neoboutonia macrocalyx, Pygeum africanum, Strombosia scheffleri, Syzygium guineense and others.
Between 1 200 and 2 700 m, with over 2 200 mm of rainfall occurs the Ficalhoa-Afrocrania forest. Pillar wood (Cassipourea malosana) becomes plentiful in some forest areas of Mount Kadam, Mount Elgon and the Imatong Mountains between 2 000 and 3 000 m. The Chrysophyllum forest is part of the impenetrable forest and covers about 30 000 ha of the Rukiya Mountains in south-western Uganda, between 1 400 and 2 400 m; the higher range is dominated by Chrysophyllum while in the lower range it is dominated by grey plum (Parinari excelsa). Prunus is locally dominant. The most abundant trees are, on the hilltops, Chrysophyllum gorungosanum, Macaranga kilimandscharica and Olea hochstetteri and on hillslopes the latter with Faurea saligna which forms, in places almost pure stands, 20 m tall. Other species of the upper storey reaching about 30 m, are: Olinia usambarensis, Podocarpus milanjianus, Polyscias fulva and Rapanea rhododendroides.
On upper hillslopes, the forest is normally taller and denser than on the ridges. There is a well-defined dominated tree stratum, around 18 m high with Allophyllus macrobotrys, Cassipourea ruwenzorensis. The understorey has many Rubiaceae. A common shrub is Cyathula uncinulata.
- In the intermediate lower zone occur coniferous forests (see below).
- The drier lower type is not represented in Uganda. The intermediate one is characterized by bamboo; the largest areas of mountain bamboo occur on the Ruwenzori mountains, the Virunga volcanoes and the Echuya reserve on the Ruchiga mountains in the south west. The bamboo Arundinaria alpina is the main species, growing over 10–12 m high in dense even stands on good soils. The upper zone usually consists of low woodland from 12 to 18 m, with Hagenia abyssinica, accompanied by Rapanea rhododendroides and Hypericum or Sambucus.
c) Swamp forests
In the swamp forests of the lake Victoria belt the following species occur: Bombax reflexum, Cathormion altissimum, Cleistanthus polystachys, Erythrina excelsa, Euphorbia teke, Macaranga schweinfurthii, Mitragyna stipulosa, Parkia filicoidea, Phoenix reclinata, Pseudospondias microcarpa, Spondianthus preussii, Treculia africana, Beilschmiedia ugandensis, Voacanga obtusa. The canopy seldom exceeds 24 m, the lower stratum consisting mainly of Raphia, Tabernaemontana and Voacanga, sometimes with Phoenix reclinata.
In the south-west of Uganda forests occur sporadically on swampy ground with Myrica kandtiana, Rapanea rhododendroïdes and Syzygium cordatum, with a canopy height of 10 m approximately.
d) Forests with a significant proportion of coniferous species exist in several places 1. In the lower and intermediate zones of the upland forests some small patches of Juniperus forest (Juniperus procera) occur which are presumably relics of some larger communities. In the same zone a mixed forest exists with Podocarpus gracilior and Juniperus procera, in association with Ocotea, Olea and other upland hardwoods. Along the western shore of lake Victoria, on elevated lake and river deposits, on clayey soils occurs an evergreen two storeyed forest with Podocarpus usambarensis var. dawei and Baikiaea eminii as dominant trees. Podocarpus has been heavily exploited. In some places P. usambarensis is replaced by P. milanjianus. Most of the exploited areas have an understorey of Lasiodiscus milbraedii. The upper canopy reaches 30 m and the lower storey 15 m.
Open broadleaved forests (NHc/NHO)
In the extensive grasslands (e.g. those of the Ruwenzori national park) some areas, especially around the crater lakes, are quite densely wooded, the other having only scattered trees interrupted by termite mounds bearing thickets. The woody species include Acacia spp., Balanites aegyptiaca, Albizia spp., Ficus spp. The termite mounds often have Euphorbia candelabrum, Capparis tomentosa and Grewia similis.
Parts of Teso, Lango, Acholi and Karamoja districts, with 1 000–1 250 mm annual rainfall, are covered by an open grassland with Butyrospermum paradoxum (shea butter nut), often accompanied by Combretum and associated species.
The Acacia-Themeda and wooded grasslands with Combretaceae cover large areas south of the Katonga valley extending in a zone 100–150 km wide north of the Tanzanian border. Acacia gerrardii and A. polycantha are the most common. Where there is an increase in effective rainfall (central Uganda) the Acacia-Themeda wooded grassland is replaced by the combretaceous wooded grassland and woodland with about 22 species of Combretum, the most common being C. collinum and C. molle. Terminalia spp. also occur, sometimes forming a Terminalia woodland (these stands are damaged by elephants which debark the trees, as has been noticed in Kabalega national park).
Woodland formations most similar to the “miombo” woodlands of Tanzania are found in the north-west (West Nile). Characteristic trees are Isoberlinia doka, Daniellia oliveri and Afzelia africana.
Finally over relatively small areas (north-west of Lira, north-east of Arua, west of Kampala - Hoima road) open stands of Borassus aethiopum occur on sandy soils with mobile ground water.
Shrub vegetation (nH)
In northeast Uganda (Karamoja) a dry type of bushland is found, which corresponds to a rainfall of 500–750 mm per year; some authors consider it to have been derived from dry semi-evergreen woodland by degradation through overgrazing and erosion. The vegetation consists of thorny bushes with annual grass. Studies have revealed about 500 species belonging to 30 families. Genera most represented are Commiphora, Acacia, Euphorbia, Grewia.
Between 3 000 and 4 000 m the upland forest on the Ruwenzori and the Virunga volcanoes is interpreted with ericaceous woodland, consisting of twisted ang gnarled trunks of Philippia trimera, Rapanea rhododendroïdes, Senecio erici-rosenii, S. adnivalis and Hypericum spp. In the same area Dendrosenecio woodland and wooded grassland, up to about 7 m in height, can also be found. Another type of high altitude vegetation is the Helichrysum shrub up to 3 m, abundant on the Ruwenzori.
1.1.2 Present situation of the woody vegetation
Present areas
Areas of natural woody vegetation estimated at end 1980
(in thousand ha)
Broadleaved | NHCf1uv | NHCf1uc | NHCf1m | NHCf1 | NHCf2i | NHCf2r | NHCf2 | NHCf | NHCa | |
100 | 125 | 440 | 665 | 40 | 45 | 85 | 750 | ε | ||
NHc/NHO1 | NHc/NHO2i | NHc/NHO2r | NHc/NHO2 | NHc/NHO | NHc/NHOa | nH | ||||
(1 300) | (3 200) | (750) | (3 950) | (5 250) | (1 600) | 100 | ||||
Bamboo | NHBf1uv | NHBf1uc | NHBf1m | NHBf1 | NHBf2i | NHBf2r | NHBf2 | NHBf | NHBa | |
2 | 2 | 13 | 13 | 15 | ε | |||||
Broadleaved and bamboo | NH.f1uv | NH.f1uc | NH.f1m | NH.f1 | NH.f2i | NH.f2r | NH.f2 | NH.f | NH.a | |
100 | 125 | 442 | 667 | 40 | 58 | 98 | 765 | ε |
- According to (11), the reserved forests covered in 1979 641 000 ha and were being cleared at a rate of about 1.7% per year, which corresponds with the area mentioned in (5) for 1972 of 732 000 ha. Applying the percentages of (5) the area of productive reserved forest can be estimated at 415 000 ha. About 100 000 ha of these are assumed to be undisturbed, the balance being under management. For the non-reserved forests which covered 150 000 ha in 1972 (5) the assumption was made that they disappear at 2% per year, (somewhat quicker than the reserved forests) resulting in about 125 000 ha for 1980, all being exploited (NHCf1uc).
- According to (6) 45 000 ha of closed forests are reserved for protection purposes (NHCf2r).
- Forest fallow (NHCa) is assumed to occupy only small areas.
- The assessment of woodland areas (NHc/NHO) is very tentative for lack of information outside forest reserves. A general land use distribution has been used, derived from documents (4) and (5).
Land use in Uganda
(in thousand ha)
Land use class | Approximate area |
Reserved forests and woodlands | 1 520 |
Reserved parks and game reserves | 1 470 |
Agriculture | 4 760 |
Urban areas | 70 |
“Sleeping sickness affected area” | 140 |
Other land | 11 730 |
Total land area | 19 690 |
“Other land” includes 125 000 ha of closed forests outside forest reserves (see above). About half of the “other land” is considered to have some kind of tree vegetation, resulting in 5.8 million ha, of which 1 million is assumed to be productive. The total area of productive woodlands (NHc/NHO1), including about 300 000 ha of woodlands inside the forest reserves (6) (which are considered productive in totality), is therefore 1.3 million ha. If the same proportion is used for the “reserved parks and game reserves”, the total area of woodlands unproductive for legal reasons (NHc/NHO2r) amounts to 750 000 ha approximately.
Of the 4.8 million ha considered as unproductive woodlands one third is assumed tentatively to be affected by agriculture (NHc/NHO a) while the remaining two thirds (3.2 million ha) would correspond to woodlands of poor stocking (NHc/NHO2i). All these estimates will have to be reviewed when a general land use map will be available and they have been indicated with brackets in the table.
- The area of “heath and shrub vegetation” was estimated at 100 000 ha. (10) mentions an area of 118 000 ha for “bamboo, heath etc.”
Ownership
As already mentioned, all closed forests (except 125 000 ha) are reserved. According to (2) 82% correspond to the central government forest service and 18% to the local government forest services.
There is no information about the ownership of the extensive non-reserved open woodlands outside the reserved parks and game reserves. Most probably they are also in their majority under the control of the central or local government forest services.
Legal status and management
According to the “1980 United Nations List of National Parks and Game Reserves” there are three national parks - Kabalega (ex-Murchison Falls), Ruwenzori (ex-Queen Elizabeth) and Kidepo Valley - covering a total area of 729 000 ha and 13 game reserves with a total area of 972 000 ha. The present overall area of national parks and game reserves is some what higher than the one given above (1 701 000 versus 1 470 000 ha) but this may not affect significantly the area of woodlands unproductive for legal reasons (NHc/NHO2r), the more so as it is said, in the same document, that “extensive destruction” took place in 1979 in the game reserves.
In the closed forests the management is based on the application of uniform system with post-harvest silvicultural treatment and a rotation of 60–80 years, to produce harvestable trees of DBH≥ 52 cm (5ft girth) (2). The conversion to the uniform system is done in one or two cycles. In the latter case, an intermediate felling cycle is introduced of about 30–40 years, this to prevent trees becoming overmature, or for supply reasons.
Through application of this management system it is hoped to increase the production from 1–1.5 m3/ha/year to 6–7 m3/ha/year. A special facet of the management is the protection needed against elephants (population and area control) causing damage by browsing, debarking and trampling (2).
Enrichment planting is carried out in two regions in the Budongo forest with Maesopsis eminii and Khaya sp. and in the Mabira forest with Maesopsis eminii. With this latter species it is hoped to get a final harvest of 120 m3/ha in 30 years, while for Khaya sp. a rotation of 60–70 years will be needed (5). Up to 1971 about 8 000 ha are reported to have been treated with enrichment planting (8). In (6) an area of 2 500 ha of enrichment planting is reported for the year 1973–74.
Forest utilization
Log harvesting
People are allowed, for their own personal domestic use to take reasonable quantities of forest produce from forest reserves and public land without restriction, provided that no “reserved trees” or planted trees are taken. All other harvesting from both forest reserves and unreserved public land is controlled (2). A major part of the forest industries was taken over by government in 1972 as a result of the departure of the Asians. They are run by Wood Industries Corporation (WICO) (11).
Felling, bucking and skidding are either manual or mechanized (skidding of logs by farm tractors). Species are divided into a compulsory class (species which have to be cut) and an optional class (species which may be harvested but without obligation), and a fee must be paid according to the volume taken out. Fees are higher for the most valuable species. For the compulsory species, an allowable cut is imposed, while for the other category the cut is generally free. This fee system has been changed over time, and (5) claims that “it gives no real basis anymore for the value of the exploited loge”.
The commercial timber supply comes from the accessible and productive high forest and from the plantations. The species most harvested are: nongo, mugavu (Albizia spp.) alstonia (Alstonia spp.), osan (Aningeria altissima), antiaris (Antiaris toxicaria), lufugo, mukomakoma, akasinsa (Celtis spp.), white star apple, munyamata, monkey star apple (Chrysophyllum spp.), mvule (Chlorophora excelsa), muhimbi, Uganda ironwood (Cynometra alexandri), gedu, sapele, muyovu, utile (Entandrophragma spp.), african mahogany, tido (Khaya spp.), nkoba, mukusu (Lovoa spp.), musizi (Maesopis eminii), mucence (Newtonia buchanani), mpewere (Piptadeniastrum africanum), mubura (Parinari excelsa), podo (Podocarpus spp.). According to (5) the merchantable volume of the untreated tropical high forest was from 25 to 40 m3 per ha, but (8) quotes that this volume increases to 70–100 m3/ha as a result of non-commercial species becoming commercial, which seems rather high. The average output per ha (VAC) for the whole country is estimated at 27 m3/ha, although it is realized that the best forests may produce 50 m3/ha or more.
Total production of sawlogs and veneerlogs was, according to the FAO Yearbook of Forest Products 1966–1977 as follows:
Period | 1966–70 | 1971–75 | 1976 |
Average annual production (in thousand m3) | 142 | 157 | 106 |
However (9) gives an average for the 1971–75 period of 173 000 m3 per year of sawlogs.
From 1973 there is a production of coniferous sawlogs and veneerlogs estimated at 14 000 m3 per year. The areas covered by forest exploitation should amount approximately now at 4 000 ha per year (106 000 m3/27 m3).
Other forest products
Fuelwood production is estimated at 13 million m3 per year from 1972 to 1977 (FAO Yearbook of Forest Products). Most of it is extracted from the open woodlands and wooded grasslands. Part of the firewood produced is converted into charcoal, used in households and industry. The latter used also imported charcoal from Kenya up to 1975 when this trade was prohibited. Since then demand has been met locally (11). According to (9) consumption (households and industry) was about 80 000 tons in 1974. (5) estimated that in the early 70's around 10 million m3 of fuelwood and 700 000 m3 of poles were cut annually by the subsistence sector of the economy.
Bamboo has a considerable local importance as a building material. According to (5) however, only two areas were systematically exploited and regulated in 1973.
The same source mentions that a small amount of gum arabic, enough to satisfy local demand is collected.
1.1.3 Present situation of the growing stock
The following table indicates the standing volumes at end 1980.
Growing stock estimated at end 1980
(totals in millions m3)
NHCf1uv | NHCf1uc | NHCf1m | NHCf2 | NHc/NH01 | |||||||||||
VOB | VAC | VOB | VOB | AAC | VOB | VOB | VAC | ||||||||
m3/ha | total | m3/ha | total | m3/ha | total | m3/ha | total | m3/ha | total | m3/ha | total | m3/ha | total | m3/ha | total |
180 | 18 | 27 | 2.7 | 120 | 15 | 120 | 53 | 0.4 | 0.18 | 80 | 7 | 20 | 26 | 1 | 1.3 |
The annual allowable cut (AAC) over 50 cm DHB, based on (5), is about 0.4 m3/ha/year for the compulsory and optional species.
According to (11), the estimated growing stock over 50 cm DBH in the natural high forest is around 20 m3/ha. If the felling limit is reduced to 30 cm DBH, there is an additional volume of 10.9 m3/ha. (5) gives for the southern part of the Kibale forest, an average volume per ha, all species, 20 cm DBH and over, of 154.4 m3 and 50 cm DBH and over, of 69.3 m3/ha.
1.2 Plantations
1.2.1 Introduction
Planting of coniferous species started in 1941 on an experimental scale, and was expanded on a larger scale in 1946. In the western part of the country planting schemes were started in 1948 and 1949 at Kyehara and Lendu respectively (3). First species planted was Cupressus and pines were introduced afterwards. Hardwood plantations are based on Eucalyptus spp. and have become a major source of supply for fuelwood and poles. Planting of indigenous hardwood species have presented problems yet to overcome.
1.2.2 Areas of established plantations
Industrial plantations
Areas of established industrial plantations estimated at end 1980
(in thousand ha)
Category | Species | Years | 76–80 | 71–75 | 66–70 | 61–65 | 51–60 | 41–50 | before 41 | Total |
Age class | 0–5 | 6–10 | 11–15 | 16–20 | 21–30 | 31–40 | > 40 | |||
PH.1 = PHL1 | Timber species (see below) | 0.5 | 0.7 | 0.5 | 0.3 | 0.2 | 0.1 | 2.3 | ||
PS.1 | Cupressus spp. | 1.0 | 1.2 | 0.8 | 0.3 | 0.5 | 0.2 | 4.0 | ||
Pinus patula | 0.3 | 0.6 | 1.5 | 1.1 | 0.5 | 4.0 | ||||
P. radiata | ε | ε | 0.3 | 0.2 | 0.5 | |||||
P. caribaea | 0.5 | 1.0 | 0.8 | ε | 2.3 | |||||
Others | 0.1 | 0.2 | 0.2 | 0.1 | ε | ε | 0.6 | |||
Subtotal PS.1 | 1.9 | 3.0 | 3.3 | 1.8 | 1.2 | 0.2 | 11.4 | |||
P..1 | Total industrial plantations | 2.4 | 3.7 | 3.8 | 2.1 | 1.4 | 0.3 | 13.7 |
Previous table is based on (6) for areas up to mid 1974, but with a reduction from 1970 onwards of 50%. From this year a tentative estimate was made, based on (11), which states that about 16 000 ha of softwood plantations for industrial use existed in 1976. (5) mentions that the main species used in the hardwood plantations for timber (PHL1) are: Khaya spp., Olea sp., Fagara sp., Tectona grandis. The area in 1972 amounted according to the same source, to about 2 100 ha.
In high altitude areas species used for the softwood plantations are mainly P. patula and Cupressus lusitanica. P. caribaea and P. oocarpa are planted in medium and low altitude areas.
Other plantations
There are also Eucalyptus plantations producing fuelwood and poles which are operated on a coppice system with two coppice rotations following the original planting. It is estimated that about 32 000 ha of fuel and pole plantations exist in the country at end 1980.
1.2.3 Plantation characteristics
Species | Rotation (years) | M.A.I. (m3/ha/year) | Final cut (m3/ha) | Thinnings (m3/ha(age) | Source |
Cupressus lusitanica 1 | 25 | 11.2–32.1 | 138–353 | 12–48 (7) | |
61–192 (14) | (5) | ||||
69–209 (20) | |||||
Pinus spp. 2 | 25 | 7.6–35.0 | 88–460 | 12–41 (8) | |
43–172 (15) | (5) | ||||
48–203 (20) | |||||
“Softwood” | 15 | 20.0 | 200 | ? | (11) |
30 | 18.7 | 380 | 60 (12) | (11) | |
120 (20) | |||||
Eucalyptus spp. | 7 | 20.0 | 140 | (11) | |
(fuel) | 5 | 200-52.0 | 100–260 | (5) | |
(poles) | 14 | 12.9–47.1 | 180–660 | (5) |
1 For Cupressus lusitanica, figures mentioned correspond with site qualities 12 to 22.
2 For Pinus, figures mentioned correspond with site qualities 50 to 100.
2. Present trends
2.1 Natural woody vegetation
2.1.1 Deforestation
Average annual deforestation
(in thousand ha)
Periods
1976–80 and | 1981–85 (projections) | ||||
NHCf1uv | NHCf1uc | NHCf1m | NHCf1 | NHCf2 | NHCf |
3 | 7 | 10 | ε | 10 |
According to (11) the reserved natural high forests have been reduced by 12% “during the last years”, referring probably to the period between 1972 (date of last inventory (5)) and 1978 (last year before report) or 1.7% per year. Other reports state that the natural high forest is being subject to a certain pressure “due to other landuses”.
Deforestation in savannas is mainly due to alienation to other uses (permanent agriculture especially) and to a much lesser extent to forest plantations. According to the available information the shifting cultivation does not present a serious problem and is estimated to account for not more than 5 000 ha per year (mainly in woodlands outside forest reserves) which are to be added to 35 000 ha of deforestation due to permanent agriculture and other uses including forest plantations.
2.1.2 Degradation
One case of degradation is the one occurring in the Podocarpus-Baikiaea forests which are invaded by Lasiodiscus sp. after exploitation. Large areas of previously valuable closed forest have been degraded to almost pure stands of Lasiodiscus of small height.
In the woodlands and wooded grasslands degradation is mainly the consequence of fire and overgrazing. Most of the grasslands with or without tree vegetation, in the plains and hilly country below 1 600 m, are swept by fires during the two annual dry seasons. However, where they extend right up to the boundaries of the forests, and fires are prevented, there is a natural tendency for the forest trees to invade the abandoned cultivated lands (1). On the other hand if there is much grazing, the reduction of the grass cover seems to prevent the conversion of wooded grasslands into woodlands. Main causes are trampling of the ground by cattle, increased run-off and reduced percolation. The succession in this case is directed towards bushland or bush grassland. This occurs in particular in the heavily grazed areas of northeastern Uganda, with a rainfall of about 800 mm (7). Grazing, fire and effective rainfall are often interrelated in such complex ways that it is impossible to predict the consequences of variations in their relative importance.
One of the most striking features of the Uganda landscape, according to (1), are the large patches of elephant grass Pennisetum purpureum, which constitutes a desirable natural fallow (7). The same authors mention that the areas of elephant grass east of Ruwenzori and in Bunyoro may indicate areas where well-worked Terminalia grassland has been intensively farmed with the result that trees and short grass have been replaced by Pennisetum. If left undisturbed the elephant grass thicket is soon invaded by shrubs and bushes, such as Acanthus pubescens, Vernonia spp., Clausena spp., Acalypha spp., and later pioneer trees appear such as Albizia and Maesopsis. However, it is thought unlikely that human activities alone would account for the large areas of wooded grasslands separating many of the forests.
(7) mentions that the most isolated dense forest in the West Nile province (Zola forest) is being prevented to spread by both fire and elephants. The latter cause damage when they become too numerous by trampling, eating the seedlings and debarking many trees (mainly Albizia, Chrysophyllum, Cola, Cordia and Khaya).
2.1.3 Trends in forest utilization
One change likely to occur is a decrease of the exploitable minimum diameter to 30 cm for some species. However, the corresponding increase on the output per ha should be modest (around 2 m3/ha). Charcoal consumption is expected to reach 250 000 tons by 1985.
2.1.4 Areas and growing stock at end 1985
Areas of natural woody vegetation estimated at end 1985
(in thousand ha)
Broadleaved | NHCf1uv | NHCf1uc | NHCf1m | NHCf1 | NHCf2i | NHCf2r | NHCf2 | NHCf | NHCa | |
100 | 110 | 405 | 615 | 40 | 45 | 85 | 700 | ε | ||
NHc/NHO1 | NHc/NHO2i | NHc/NHO2r | NHc/NHO2 | NHc/NHO | NHc/NHOa | nH | ||||
(1 215) | (3 110) | (725) | (3 835) | (5 050) | (1 620) | 100 | ||||
Bamboo | NHBf1uv | NHBf1uc | NHBf1m | NHBf1 | NHBf2i | NHBf2r | NHBf2 | NHBf | NHBa | |
2 | 13 | 13 | 15 | ε | ||||||
Broadleaved and bamboo | NH.f1uv | NH.f1uc | NHcf1m | NH.f1 | NH.f2i | NH.f2r | NH.f2 | NH.f | NH.a | |
100 | 110 | 282 | 490 | 41 | 58 | 98 | 715 | ε |
Growing stock estimated at end 1985
(in million m3)
NHCf1uv | NHCf1uc | NHCf1m | NHCf1 | NHCf2 | NHCf | NHc/NHO1 | |||
VOB | VAC | VOB | VOB | AAC | VOB | VOB | VOB | VOB | VAC |
18 | 2.9 | 13 | 49 | 0.16 | 80 | 7 | 87 | 24 | 1.2 |
2.2 Plantations
Industrial plantations
(11) mentions as a fair estimate an annual planting programme of 1 600 ha per year. However, it is estimated that total annual planting rate of industrial plantations will not exceed 900 ha, of which 200 ha of “other hardwood species” and 700 ha of coniferous species.
Areas of established industrial plantations estimated at end 1985
(in thousand ha)
Category | Species | Years | 81–85 | 76–80 | 71–75 | 66–70 | 56–65 | 46–55 | before 46 | Total |
Age class | 0–5 | 5–10 | 11–15 | 16–20 | 21–30 | 31–40 | > 40 | |||
PH.1 = PHL1 | Timber species | 1.0 | 0.5 | 0.7 | 0.5 | 0.4 | 0.2 | ε | 3.3 | |
PS.1 | Cupressus spp. | 1.5 | 1.0 | 1.2 | 0.8 | 0.5 | 0.3 | 0.2 | 5.5 | |
Pinus patula | 0.5 | 0.3 | 0.6 | 1.5 | 1.3 | 0.3 | ε | 4.5 | ||
P. caribaea | 1.0 | 0.5 | 1.0 | 0.8 | ε | 3.3 | ||||
P. radiata | ε | ε | 0.4 | 0.1 | 0.5 | |||||
Others | 0.5 | 0.1 | 0.2 | 0.2 | 0.1 | 1.1 | ||||
Subtotal PS | 3.5 | 1.9 | 3.0 | 3.3 | 2.3 | 0.7 | 0.2 | 14.9 | ||
P..1 | Total industrial plantations | 4.5 | 2.4 | 3.7 | 3.8 | 2.7 | 0.9 | 0.2 | 18.2 |
Other plantations
The planting rate of fuelwood and pole plantations is tentatively estimated at 1 000 ha per year, resulting in a total area of 37 000 ha in 1985.
Bibliography
Snowden, J.D. 1953 “The Grass Communities and Mountain Vegetation of Uganda” - London
Mugwanya, M. 1961 “The Forests and the Forest Administration of Uganda” - Entebbe
Uganda Forest Department 1969 “Estimation of Probable Outturn from Uganda's Softwood Plantations 1960–1979” - Technical note no. 160/69 - Entebbe
Uganda Ministry of Manning and Economic Development 1973 “Statistical Abstracts 1972” - Entebbe
Lockwood Consultants Limited 1973 “Forest Resource Development Study, Republic of Uganda” - Final Report: Main Volume, Annexes 1 to 4 - Toronto (Canada)
Ministry of Agriculture and Forestry, Forest Department 1974 “Annual Report for the July 1973 to June 1974” - Entebbe
Lind, E.M. and Morrison, M.E.S. 1974 “East African Vegetation” - Longman - London
Karani, P.K. 1975 “Uganda Forest Department Country Report for FAO Conference on moist Tropical Forests 1975” - Entebbe
Forest Department 1976 “Progress Report for Uganda” - Fourth session of African Forestry Commission (Bangui) - Entebbe
FAO 1979 “Future Requirements for Forest Products” - based on the work of E. Sakman - FO:UGA/74/019 Project Working Document no. 6 - Rome
Kir, A. 1979 “Draft of Terminal Report: Forest Development” - UGA/74/019 - Rome
La République du Zaïre occupe une surface totale de 2 344 885 km2 entre les parallèles 5°20'N et 13°28'S et les méridiens 12°10' et 31°15'E, dont plus de 77 000 km2 sont recouverts par les eaux, soit une surface de terres évaluée à 2 267 600 km2. Le territoire se présente comme un quadrilatère de forme sensiblement carrée, les dimensions extrêmes étant de 2 139 km dans le sens est-ouest et de 2 094 km dans le sens nord-sud. Le pays est presque entièrement enclavé au centre de l'Afrique, n'ayant qu'une façade de 40 km sur l'Océan Atlantique à l'embouchure du fleuve Zaïre entre la province angolaise du Cabinda et le reste de l'Angola sur la rive gauche du fleuve (34).
Le territoire du Zaïre est tout entier occupé par le bassin du fleuve du même nom, vaste cuvette souvent marécageuse, dont l'altitude moyenne ne dépasse pas 400 m, les points les plus bas se trouvant au nord-ouest dans la région des lacs Tumba et Mayi-Ndombe (ex-Léopold II), vers laquelle convergent les principaux affluents de la rive gauche. Ouverte seulement à l'ouest, la dépression centrale est fermée partout ailleurs par des reliefs bordiers. Au nord, entre les cours du Zaïre et de l'Oubangui, s'étendent des plateaux monotones (entre 600 et 800 m). Au sud, d'autres plateaux, vastes et étagés, s'élèvent progressivement vers le sud-est et atteignent dans le Shaba 1 000 à 2 000 m. A l'est, le socle ancien se relève fortement aux abords des grands effondrements de la Rift Valley occidentale. Les altitudes atteignent 4 500 m dans le massif volcanique des Virunga, à la frontière du Rwanda; dépassent 5 000 m dans le massif du Ruwenzori, qui marque la frontière avec l'Ouganda; atteignent 2 000 m dans les Montagnes Bleues, à l'ouest du lac Mobutu Sese Seko, et dans les monts Kivu, à l'ouest du lac qui porte leur nom (d'apres l'atlas Jeune Afrique).
77% du territoire se trouve à moins de 1 000 mètres d'altitude et 0,8% seulement au-dessus de 2 000 mètres.
On peut distinguer:
un climat équatorial au voisinage de l'équateur constamment chaud et humide, avec 140 à 160 jours de pluie par an, un maximum de précipitation en Avril et Octobre et un minimum en Janvier et Juillet. Dans les zones de faible altitude (cuvette) la pluviométrie annuelle est comprise entre 1 800 et 2 200 millimètres;
un climat tropical, au delà des parallèles 3°N et 3°S avec l'apparition d'une véritable saison sèche dont la durée augmente avec l'éloignement de l'équateur (4 mois à Kinshasa, 5 mois à Kamina et 6 mois à Lumumbashi);
des variantes altitudinales dans les régions montagneuses de la partie orientale des provinces du Kivu et du Shaba, où la pluviométrie peut atteindre jusqu'à 3 000 mm et les températures moyennes décroissent à raison de 1°C pour 180m de dénivellation.
Les parties les plus sèches se trouvent sur la côte atlantique au Bas-Zaïre (810 mm de pluie à Banana où se fait sentir l'influence du courant froid de Benguela) et dans les parties basses du Shaba où la pluviométrie peut descendre aussi en dessous de 1 000 mm.
Les chiffres officiels font état d'une population de 21 368 000 personnes en 1970 et 25 569 000 à la fin de 1975 soit un taux d'accroissement durant cette période de 3,4% par an, qui, projeté sur 1980, correspond à une population de 30,2 millions environ. Les projections des Nations Unies et de la FAO donnent un chiffre légèrement inférieur (28,0 à 28,3 millions). La population rurale en 1975 atteignait 21 millions d'habitants, soit une densité moyenne de 9,3 habitants au km2, variant de 5–7 pour les provinces du Shaba, de l'Equateur et du Haut-Zaïre à près de 28 pour le Bas-Zaïre. La population agricole est estimée par la FAO à 20,6 millions de personnes en 1979 (soit 3,4 millions de familles environ) croissant au taux de 2,0%, nettement inférieur à celui de la population totale. Bien qu'accentuée en certains endroits, la pression de l'agriculture sur la végétation reste dans l'ensemble faible. D'immenses zones de forêt restent à l'abri des défrichements du fait en particulier du regroupement de la population le long des principales voies d'accès terrestres ou fluviales. Là où la culture itinérante a pris sur la forêt, la durée des jachères ne se réduit pas en général d'une manière significative.
1. Situation actuelle
1.1 Végétation ligneuse naturelle
1.1.1 Description des types de végétation
La description qui suit utilise essentiellement le travail de J. Lebrun et G. Gilbert dans “Une classification écologique des forêts du Congo” (5) et reprend les dénominations utilisées dans la carte de végétation de R. Devred (11) (12). Elle est presentée dans le cadre des grandes catégories de végétation utilisées dans cette étude.
Formations forestières feuillues denses (NHC)
(a) Les forêts ombrophiles sempervirentes sur sol ferme de basse et moyenne altitude (“forêts ombrophiles équatoriales” de Lebrun et Gilbert) représentent environ un tiers des forêts denses sur sol ferme du pays (entre 35 et 40 millions d'ha). Elles s'observent surtout dans une large auréole autour de la cuvette centrale (occupée dans une large proportion par des formations forestières édaphiques des zones basses marécageuses et inondables). Elles constituent le noyau climax dont dérivent une partie des forêts semi-décidues et représentent le secteur oriental de l'ensemble des forêts ombrophiles équatoriales de la région guinéenne qui s'étend du Libéria au Zaïre. Parmi les espèces arborescentes caractéristiques on peut citer des Cesalpiniées comme Brachystegia laurentii, Gilbertiodendron dewevrei, G. ogoouense, Julbernadia seretii, des Ebenacées (Diospyros spp.), des Olacacées (Diogoa zenkeri, Heisteria parvifolia), des Annonacées (Isolona thonneri, Polyalthia suaveolens, des Myristicacées comme Staudtia stipitata (niové du commerce). Les deux premières essences, comme d'autres Cesalpiniées en forêt dense africaine (cf. peuplements de Monopetalanthus durandii au Gabon) constituent des peuplements purs ou presque purs de grande étendue (9). Les peuplements de Gilbertiodendron dewevrei se retrouvent au Congo et marginalement au Cameroun et en République Centrafricaine.
(b) Les forêts denses humides semi-décidues sur sol ferme de basse et moyenne altitude (“Forêts mésophiles semi-caducifoliées” de Lebrun et Gilbert) peuvent être divisées en trois groupes (5);
les “forêts semi-caducifoliées subéquatoriales et guinéennes” se retrouvent dans ou en bordure du massif forestier sempervirent équatorial et constituent des “stades syngénétiques antérieurs au climax” (“forêts denses humides semi-décidues de dégradation” suivant Devred). Parmi les espèces caractéristiques on peut citer des Légumineuses - Pericopsis elata (afrormosia ou assamela ou kokrodua du commerce), Copaifera soyauxii, Dialium spp. Gossweilerodendron balsamiferum (tola du commerce, particulièrement abondant au Mayumbe dans le Bas-Zaïre), Oxystigma oxyphyllum (tchitola du commerce) Scorodophloeus zenkeri - les Celtis, des Méliacées - Entandrophragma angolense (tiama du commerce), Guarea cedrata et G. thompsonii (bossé du commerce) - etc..;
les “forêts semi-caducifoliées subéquatoriales et periguinéennes” qui sont des forêts climax ou édaphiques des régions périphériques à la cuvette centrale, dans les territoires de savanes guinéennes avec comme espèces caractéristiques Albizia zygia, Bombax flammeum, Celtis kraussiana, Cordia chrysocarpa, Lovoa trichilioides (dibetou du commerce), Millettia spp. (wenge du commerce), Parkia spp., Pygeum africanum. Devred distingue en particulier les “forêts denses humides semi-décidues subéquatoriales et guinéennes à Cynometra alexandri” co uvrant plus d'un demi-million d'hectares aux confins orientaux des provinces du Haut-Zaïre et du Kivu;
les “forêts semi-caducifoliées, semi-tropicales à distribution zambézienne” constituent des noyaux de forêt dense, au milieu des forêts claires et savanes boisées du sud du pays, appelées “muhulu” et comportent une proportion très élevée d'espèces arborescentes décidues lui conférant, avec leur hauteur relativement basse (15 à 25 mètres), un aspect de forêt dense sèche; quelques espèces caractéristiques sont Baphia bangweolensis, Brachystegia spiciformis var. schmitzii, Entandrophragma delevoyi et Manilkara sp.
(c) Les forêts denses submontagnardes et montagnardes représentent à l'heure actuelle probablement moins d'un demi-million d'hectares et sont confinées sur la bordure orientale de la province du Kivu.
On distingue:
les “forêts ombrophiles de montagne” (dorsale de l'Ituri, versants du Ruwenzori, volcans des Virunga, dorsale du Kivu, crêtes bordant les lacs Kivu et Tanganika) se caractérisant notamment par la présence de conifères 1 (Podocarpus milanjianus, P. usambarensis, Juniperus procera) et d'espèces feuillues telles que Alangium chinense, Ekebergia ruppeliana, Ficalhoa laurifolia, Ocotea usumbarensis;
les “forêts sclérophylles montagnardes” entre 1 500 et 3 200 mètres, qui peuvent se présenter sous la forme soit de forêts basses de 10 à 12 mètres, soit de maquis plus ou moins ouverts (et doivent être classées alors dans les formations arbustives - nH). Des espèces caractéristiques sont Agauria salicifolia, Erica arborea, Ilex mitis, Myrica salicifolia Pittosporum spp., Rapanea spp.;
les forêts sclérophylles submontagnardes à Crewia spp., Carissa edulis, Euphorbia calycina et E. dawei qui ont pratiquement disparu au Burundi et au Rwanda (sauf dans ce dernier pays dans la partie orientale) et qui se présentent souvent sous forme de maquis.
(d) Les “forêts édaphiques liées aux sols hydromorphes” revêtent au Zaïre une importance considérable. Elles couvrent environ 20 millions d'hectares dans la cuvette centrale essentiellement. Lebrun et Gilbert distinguent les catégories suivantes:
les “forêts ripicoles colonisatrices” de faible hauteur ou arbustives (et à ce dernier titre devant figurer dans la catégorie nH de cette étude), à substrat constamment ou presque constamment baigné par l'eau, sans période de drainage proprement dite. Elles comprennent notamment les franges forestières à Uapaca heudelotii formant transition entre les groupements arbustifs pionniers et les forêts marécageuses ou inondables;
les “forêts riveraines ou insulaires”, à substrat subissant des alternances de fortes inondations et d'exondaison avec une période de drainage de courte durée, comportant des espèces telles que Cleistopholis patens, Ficus mucuso, Lannea welwitschii, Oxystigma buccholzii, Pseudospondias microcarpa, Spondianthus preussii etc…;
les “forêts périodiquement inondées” avec une période d'exondaison relativement longue, à Guibourtia demeusei (bubinga du commerce) parfois en peuplements purs ou accompagnés d'autres espèces de Cesalpiniées telles que Didelotia unifoliolata, Monopetalanthus pteridophyllus, et d'autres familles, comme Oubanguia, Pachystela, Parinari et Scytopetalum;
les “forêts marécageuses”, sans période marquée d'assèchement et de drainage avec, parmi les espèces plus caractéristiques, Alstonia congensis, Berlinia heudelotiana, Entandrophragma palustre, Mitragyna ciliata, M. stipulosa, Uapaca guineensis etc..;
les “forêts vallicoles alluviales”, sur les banquettes alluvionnaires subissant des crues périodiques, avec Erythrina excelsa, Khaya nyasica, Pterygota mildbraedii, Sterculia ambacencis;
les mangroves dans le système deltaïque de l'embouchure du Zaïre et dans les lagunes intérieures en arrière de la côte atlantique, avec comme essences les plus importantes Avicennia nitida, Conocarpus erectus et Rhizophora racemosa. Leur surface est estimée dans cette étude à 50 000 hectares environ.
(e) La succession des types de forêt secondaire après défrichement par l'agriculture itinérante est bien décrite dans les documents (3) et (5). Ce dernier document distingue:
les jachères et recrûs forestiers de plaine (NHCa) “correspondant aux stades arbustifs ou arborescents initiaux de la reconstitution ou de la recolonisation forestière dans l'aire des forêts denses de plaine” et comprenant: les “friches et jachères préforestières” avec notamment Caloncoba welwitschii, Harungana madagascariensis et Trema orientalis et les recrûs forestiers, notamment les parasoleraies (Musanga cecropioides);
les stades arborescents terminaux de la reconstitution et abritant typiquement ou cohabitant avec des espèces de la forêt primitive (“vieilles forêts secondaires”), avec notamment Pycnanthus angolensis (ilomba du commerce) et Fagara spp. dans l'aire de la forêt sempervirente, et Terminalia superba (limba du commerce) et triplochiton scleroxylon (samba, ou ayous, ou obeche du commerce) dans l'aire de la forêt semi-décidue;
le recrûs et les forêts secondaires de montagne incluant les friches et jachères préforestières avec des petits arbustes et des grandes herbes du type Lobelia gibberoa et des recrûs et forêts secondaires à Polyscias fulva, Neoboutonia macrocalyx, Croton macrostachys etc.
Formations forestières feuillues ouvertes (NHc/NHO)
Les forêts claires et savanes boisées correspondent aux “forêts tropophiles” selon Lebrun et Gilbert et surtout à leurs formes altérées ou dégradées provenant des défrichements par l'homme et de l'action des feux courants. Ces deux auteurs distinguent:
les “forêts tropophiles zambéziennes”, elles-mêmes subdivisées de la manière suivante:
les formations à Berlinia giorgii et Marquesia macroura qui servent en fait de transition entre les forêts semi-décidues et les forêts tropophiles proprement dites, notamment dans les provinces du Bas-Zaïre et de Bandundu (“savanes guinéennes teintées d'éléments soudano-zambéziens à l'ouest du lac Leopold II”, selon Devred) et dans le secteur lundien du domaine zambézien (sud du Kasai occidental). D'autres espèces caractéristiques sont Brachystegia mimosaefolia, Daniellia alsteeniana, Guibourtia coleosperma, Uapaca nitida, U. sansibarica;
les formations à Balanites quarrei, Boscia caloneura et Fagara homblei dans les sols frais de la province du Shaba;
les formations à Brachystegia macrophylla et Monotes spp.;
les “forêts tropophiles soudaniennes” sont peu représentées sauf aux confins de la République Centrafricaine et du Soudan (“forêts claires tropophiles soudaniennes” selon Devred). Parmi les espèces caractéristiques on peut citer Butyrospermum parkii, Daniellia oliveri, Detarium senegalense, Erythroxylon manii, Isoberlinia spp. (dont I. doka), Lophira lanceolata, Monotes kerstingii, Parinari kerstingii, Parkia biglobosa et Uapaca somon.
La carte de végétation de Devred offre une classification plus détaillée des formations mixtes forestières et graminéennes laquelle comprend outre les deux catégories déjà mentionnées ci-dessus, les classes suivantes:
“savanes guinéennes teintées d'éléments soudano-zambéziens;
“forêts denses sèches dégradées remplacées par des forêts claires tropophiles et îlots de savanes zambéziennes”;
“forêts claires tropophiles dégradées”;
“savanes steppiques zambéziennes des plateaux Bateke et du Kwango méridional”;
“savanes steppiques zambéziennes des hauts plateaux katangais”;
“savanes boisées sur sols alluvionnaires à Acacia sieberiana var. woodii et A. polyacantha var. campylacantha;
“forêts claires tropophiles soudaniennes”.
Bambousaies (NHB)
Dans les forêts de montagne du Kivu, entre 2 350 et 2 550 mètres, de même qu'au Rwanda et au Burundi, la “forêt feuillue-résineuse” selon Pierlot (19) est souvent constituée d'un taillis-sous-futaie claire de Podocarpus usambarensis sur un taillis d'Arundinaria alpina. Cependant l'étage de futaie est souvent très clairsemé ou même absent, de sorte que l'on se trouve en présence de véritables forêts de bambou à l'état presque pur.
Des bambousaies à Oxytenanthera abyssinica sont signalées sur la carte de végétation au 1/5 000 000ème au Shaba (région de Kamina et Lubundi, sud de Kolwezi, nord de Pweto sur la frontière zambienne) et au nord-est du pays dans la région de Mahagi et Aru, à la frontière ougandaise.
Formations (essentiellement) arbustives (nH)
Devred distingue différentes catégories de savanes arbustives dans la carte de la végétation au 1/5 000 000ème, à savoir:
“savanes arbustives guinéennes de transition, teintées d'éléments soudano-zambéziens” dans le Kwango méridional aux confins angolais des provinces du Bas-Zaïre et de Bandundu;
“savanes arbustives zambéziennes”, au Shaba entre la zone des savanes guinéennes au nord et les forêts claires tropophiles zambéziennes au sud;
“savanes guinéennes et soudano-zambéziennes arbustives en bordure des vallées” dans la région située entre les rivières Kwango et Kwilu dans la province de Bandundu;
“savanes arbustives orientales teintées d'éléments soudaniens” en bordure du lac Albert à la frontière avec l'Uganda;
“savanes arbustives de transition guinéennes - orientales, teintées d'éléments soudaniens”, aux confins nordorientaux des frontières avec le Soudan et l'Ouganda;
“savanes arbustives soudaniennes” au milieu des “forêts claires tropophiles soudaniennes”, au nord des précédentes.
Une partie des “forêts sclérophylles montagnardes et submontagnardes” (selon Lebrun et Gilbert) se présente sous une forme arbustive (cf. plus haut). Il en est de même de certaines forêts ripicoles colonisatrices à caractère soudano-zambézien “formant des rideaux ou des galeries étroites le long des cours d'eau, colonisant les marais en voie de colmatage ou succédant aux roselières ou papyraies” (5) à Mirica spp. et Syzygium cordatum ou de celles à caractère guinéen à Euphorbiacées (Alchornea cordifolia, Antidesma leptobotryum, Phyllantus floribundus).
Les “forêts sclérophylles littorales” (selon Lebrun et Gilbert) “constituent l'aboutissement de la colonisation végétale des sables littoraux et paraissent en équilibre avec le climat côtier” (5). Elles se présentent “le plus souvent sous forme de bosquets ou de boqueteaux peu étendus” (5) et couvrent une surface négligeable par rapport à l'ensemble des formations arbustives du pays.