Nigeria is located in western Africa and lies between latitudes 4
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2.4.7 Mangrove zone Mangrove vegetation depends on the coastal location of the zone, constant influence of saltish sea water(figure 7). The soil in the Mangrove zone is extremely poor and contains salt. The places, which were stabilized and are non-salt-marsh are suitable for growing of rice 
Nigeria is a large country with different types of climate. The humid subequatorial regime is typical for the southern part, the temperature is low in the mountains, the areas around the middle of the country have a tropical climate, and the tropical continental regime is observed in the north of the country. With regard to precipitation at the coastline, the eastern part records 430cm, the western region records 180 cm, the center of Nigeria records 130cm, the upper north is the driest zone and records only about 50cm. An itchy red dust is brought in by the wind from the Sahara and forms the southwest rainy weather. Temperature almost always remains approximately at the same level in the country, so rainfall can be considered a key factor affecting the formation of vegetation areas. Its level depends on the movement of air masses over the territory of Nigeria at different periods.. Read more: https://www.legit.ng/1130549-how-rainfall-determine-vegetation-distribution-nigeria.html In the northern half of the Sudanian Region (the Sudan zone of Keay, 1959a) the riparian forest is semi- deciduous but has frequently been degraded to riparian woodland. The most frequent large trees are Khaya senegalensis, Diospyros mespiliformis, Tamarindus indica, Ficusglumosa,F.sycomorus,Acaciasieberanaand,in rocky places, Adina microcephala. Sudanian transition woodland Refs.: Harrison & Jackson (1958, p. 23); Schnell (1977, p. 273, 292); White (MS, 1963). Too few species occur in sufficiently constant asso- ciation with others over sufficiently extensive areas to permit the recognition of well-defined ecological elements, though, more locally, poorly defined 'asso- ciations' can sometimes be recognized (Kershaw, 1968). Furthermore, any well-definedfloristicpattern which may formerly have existed h a s been greatly obscured because o f th e degradation most Sudanian vegetation has suffered. Most of the Sudanian Region is relatively low-lying and without pronounced relief. The climate changes gradually, and this, combined with the wide tolerances of th e species, renders difficult th e recognition o f distinct zones a n d distinct vegetation types. Some species, however, have a distinctly northern o r southern distribution, though the majority are more wide- spread. Species characteristic of the drier northern parts of the Sudanian Region include (S = Sudanian endemic): The Sudanian regional centre ofendemism 105 Transitionwoodlandwasprobablyformerlyextensive, Acaciaalbida,A.macrostachya(S),A.niloticasubsp. but only tiny remnants remain, especially in the ecotone adstringens (S), A. Senegal, A. seyal, Albizia chevalieri (S), betweenriparianforest and various types of savanna. Balanites aegyptiaca, Bauhinia rufescens (S), Boscia IntheYankariGameReserveinNigeria(White,salicifolia,Commiphoraafricana,C.pedunculata, MS, 1963) well-developed transition woodland occurs Dalbergia melanoxylon, Ficus sycomorus, Lannea humilis, on the outer fringe ofriparianforest. It is dominated by Lonchocarpus laxiflorus (S), Maerua angolensis, Pilio- Khaya senegalensis and Diospyros mespiliformis, both of stigma reticulatum (S ), Sclerocarya birrea (S ), which are regenerating freely. The more conspicuous
MS, 1963) rocky inselbergs are crowned with transition woodland dominated b y Olea capensis (including
associates are forest species and include Albizia zygia, Dialiumguiñéense,Ficuscapensis,Harungana mada- macrothyrsa,A.polyacanthasubsp.campylacantha,A. gascariensisandPachystelabrevipes. Near the western limit oftheSudanian Region, the forest of Bandia near Thiès (Schnell, 1977) is comprised of savanna and forest species. Several woodland species, including Parkia biglobosa,Adansonia digitata, Celtis (S), Cassia sieberana (S), Combretum collinum, C integrifoliaandAnogeissusleiocarpuscontributetothefragrans,C.glutinosum(S),C.molle,C.nigricans(S), 20-30 m tall canopy and assumethe habit of forest trees. Crossopteryxfebrífuga, Cussoniaarbórea,Daniellia oliveri Their forest associates are Khaya senegalensis, Morus (S), Detarium microcarpum (S), Dichrostachys cinérea, mesozygia, Ceiba pentandra andAntiaris toxicaría. Diospyros mespiliformis, Ekebergia capensis,Erythro- Transition woodland in the Sudan Republic near the eastern limit of the Sudanian Region has been described by Harrison & Jackson (1958). Important species include Terminalia glaucescens, Albizia zygia, Vitex doniana and Anogeissus leiocarpus. Sudanian woodland Most Sudanian trees have very wide geographical ranges, both longitudinal a n d latitudinal, a n d wide ecological tolerances. Well-defined centres of endemism of relatively small extent within the Region do not exist. phleum africanum, Ficus glumosa (S ), Haematostaphis barteri (S), Hymenocardia acida, Khaya senegalensis (S), Isoberlinia doka (S ), / . angolensis, Lannea schimperi, Mitragyna inermis (S), Nauclea latifolia, Parinari curatellifolia, Parkia biglobosa (S), Pericopsis laxiflora (S), Piliostigma thonningii, Prosopis africana (S ), Pseudocedrela kotschyi (S ), Pterocarpus erinaceus (S ), Steganotaenia araliacea, Sterculia setigera (S ), Stereospermum kunthianum, Strychnos madagascariensis, Swartzia madagascariensis, Syzygium guiñéense subsp. guiñéense,Terminaliaavicennioides(S),T.laxiflora(S), T macroptera (S), Trichilia emética, Vitex doniana, Tamarindus indica and Ziziphus mauritiana. Some of them extend northwards into the Sahel zone. Species characteristic of the wetter southern parts of schweinfurthiana, Protea madiensis, Terminalia glau- cescens (S) and Uapaca togoensis (S). Species occurring both in the drier and wetter parts of the Sudanian Region include: Acacia hockii, A. sieberana,Afzeliaafricana(S),Amblygonocarpus andon- gensis,Annona senegalensis, Anogeissus leiocarpus (S), Bombax costatum (S), Boswellia dalziellii (S), Bridelia ferruginea, Burkea africana, Butyrospermum paradoxum 106 Vegetation ofthe floristic regions Xeroderris stuhlmannii, Ziziphus abyssinica a n d Z . mucronata. It is convenient to divide the Sudanian woodlands into two types, though their floristic differences should not b e over-emphasized. The wetter woodlands in the south are often dominated by Isoberlinia doka. The drier northern woodlands characteristically lack Isoberlinia, except for small pockets which nearly always occur on rocky hills. Isoberlinia doka does not cross the Nile Valley, except in the extreme south, where it extends a short distance into Uganda. T h e woodlands occurring between the valley of the White Nile and the lower slopes of the Ethiopian Highlands appear to be related to Sudanian undifferentiated woodland and are briefly described below (page 107). Drier types in Nigeria The most extensive vegetation in Zamfara Forest Reserve west o f Katsina, where rainfall is approximately 700 mm per year, is Anogeissus woodland, which is kept rather open b y frequent fires and domestic animals (Keay, 1949). The area was cultivated during the firs lf o f last century but became uninhabited, probably between 1850 and 1870. The principal trees associated with Anogeissus a re : Acaciaseyal,A.Senegal,Adansoniadigitata,Albizia chevalieri, Annona senegalensis, Balanites aegyptiaca, Boswelliadalziellii,Butyrospermumparadoxum, Combre- tum glutinosum, Commiphora africana, Diospyros mespili- formis, Entada africana, Gardenia sokotensis, Hyphaene thebaica, Lannea microcarpa, L. schimperi, Lonchocarpus laxiflorus, Piliostigma reticulatum, Prosopis africana, Sclerocarya birrea, Strychnos spinosa, Tamarindus indica,
Woodland somewhat intermediate in floristic composi- tion between Isoberlinia woodland and the drier types of undifferentiated Sudanian woodland described above is found to the north of the main belt of Isoberlinia woodland. Small stands of Isoberlinia, especially /. tomentosa, occur scattered throughout, especially o n rocky hills. Relatively undisturbed woodland of this type occurs in Yankari Game Reserve in Bauchi State and has been described b y Keay (1961) and White (MS, 1963). Similar vegetation occurs in Cameroun (Mildbraed, 1932). The prevalent vegetation on the level sandy plateau in Yankari Game Reserve is a rather open woodland about 8 m high with the tallest species u p to 12 m . T h e most conspicuous trees are: Afzelia africana, Burkea th e Region h a s been very different from that o f th e bretum glutinosum, C.nigricans,Pericopsis laxiflora, laxiflora, Lannea schimperi and, in rocky places, Deta- rium microcarpum. Nearly all th e above belong to tw o families, namely, Combretaceae and Leguminosae. T h e genus Acacia, which is well represented in the drier undifferentiated Sudanian woodland, plays a very subordinate role in the wetter types. Rocky hills of hard metamorphosed sandstone have a much more diversified flora. with the drainage lines are relatively restricted. By contrast, grassland and wooded grassland on vertisols formed from Pleistocene alluvium are very extensive. The latter occupies former shallow lake basins which often extend into the Sahel zone. Their vegetation is treated collectively here. Valleyandflood-plaingrassland The Sudanian regional centre ofendemism 107 Ethiopian undifferentiated woodland (mapping unit 29b) In the extreme east o f the Sudan Republic, against th e frontier with Ethiopia, a narrow strip o f dark cracking clays o n sloping ground is dominated b y Anogeissus leiocarpus and Combretum hartmannianum with sporadic Sterculia setigera. In western Ethiopia the woodland consists chiefly of Anogeissus leiocarpus, Balanites aegyp- tiaca, Boswellia papyrifera, Combretum collinum, C. hart- mannianum, Commiphora africana,Dalbergia melano- xylon, Erythrina abyssinica, Gardenia ternifolia (lutea), Lannea schimperi, Lonchocarpus laxiflorus, Piliostigma thonningii, Stereospermum kunthianum and Terminalia brownii.
There is little published information. Pure grassland is rare. In most grasslands, both edaphic and secondary, there is an admixture of woody plants. Sudanian edaphic grassland and woodedgrassland (mapping units 62,63,and 64) Refs.: Harrison & Jackson (1958); Keay (1959a; 1960); Letouzey (1968a, p. 320-3); White (MS, 1963). Phot: Letouzey (1968a: 47). The recent geomorphological history o f africana, Anogeissus leiocarpus, Pteleopsis suberosa, Com- Zambezian Region. Hence the nature and extent of their edaphic grasslands are also dissim ilar. I n the Sudanian Lonchocarpuslaxiflorus,Terminaliaavicennioides,T.Regiongrasslandsonhydromorphicsoilsassociated Woodland and wooded grassland at the edgeof grassy flood plains ('fadamas') of theriversis of a some- what different composition and is chiefly composed of: Acacia sieberana, Adansonia digitata, Balanites aegyptiaca, Borassus aethiopum, Daniellia oliveri, Nauclea latifolia, Piliostigmathonningii, Pseudocedrela kotschyi,Terminalia macroptera, T. glaucescens, Mitragyna Tamarindus indica and Vitex doniana. Undifferentiated woodland in the Sudan Republic (mapping unit 29a) In Darfur Province Anogeissus leiocarpus occurs o n th e deeper Basement Complex soils, either in almost pure stands o r accompanied b y Combretum glutinosum, Terminalia laxiflora, Sclerocarya birrea, and Dichro- stachys cinérea. Stony ridges are dominated by Boswellia papyrifera (Wickens, 1977a). inermis, and the fan palm Borassus aethiopum. The prin- cipal grasses are Hyparrhenia cyanescens, Pennisetum u Yüklə 0,92 Mb. Dostları ilə paylaş:
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