Plant Formations in the Nigerian-Cameroonian BioProvince Peter Martin Rhind Nigerian-Cameroonian Evergreen Rain Forest These forests are often characterized by species of the Fabaceae sub-family Caesalpinioideae and species such as the endemic Calpocalyx heitzii (Fabaceae – sub- family Mimosoideae) and the regional endemic Sacoglottis gabonensis (Humiriaceae). They are more or less arranged in three strata. Large emergents and upper canopy trees reach heights of 35-50 m and include many regional endemics such as Anthonotha fragrans, Aphanocalyx margininervatus, Erythrophleum ivorensis (Caesalpinioideae), Desbordesia glaucescens (Irvingiaceae), Lovoa trichilioides (Meliaceae) and Pterocarpus soyauxii (Fabaceae). The sub-canopy at heights ranging from 20-35 m is often dominated by the endemic Calpocalyx dinklagei (Fabaceae) and regional endemics like Dialium pachyphyllum, Tetraberlinia bifoliofolia (Caesalpinioideae), Dichostemma glaucescens (Euphorbiaceae), Diogoa zenkeri, Strombosia grandifolia (Olacaceae), Greenwayodendron suaveolens (Annonaceae) and Santira trimera (Burseraceae). The under storey tends to be discontinuous and reaches about 10 m in height. Typical small trees and shrubs include endemic s like Allexis cauliflora, Rinorea albidiflora (Violaceae), Asystasia macrophylla (Acanthaceae), Crotonogyne manniana (Euphorbiaceae), Palisota ambigua (Commelinaceae) and Scaphopetalum blackii (Sterculiaceae), together with many regionally endemic species such as Diospyros preusii (Ebenaceae), Jollydora duparquetiana (Connaraceae) and Massularia acuminata (Rubiaceae). The ground flora is largely dominated by seedlings, but also includes many herbaceous species such as the endemic grass Puella schumanniana (Poaceae). Nigerian-Cameroonian Semi-Deciduous Forest Forests of this type can be found, for example, in the Campo-Ma’an area, but the relative proportions of evergreen and deciduous elements vary from place to place. In the eastern parts, the forests are characterized by a discontinuous canopy with large open areas often covered by the regionally endemic herb Haumania danckelmaniana (Marantaceae) and the regionally endemic rattans Calamus deerratus, Laccosperma opacum and Oncocalamus mannii (Arecaceae). The irregular canopy trees include the endemic Dacryodes buettneri (Burseraceae) and a number of regionally endemic species such as Celtis tessmannii (Ulmaceae), Coula edulis (Olacaceae), Distemonanthus benthamianus, Pentaclethra macrophylla, Stachyothyrsus staudtii (Fabaceae), Lophira alata (Ochnaceae), Petersianthus macrocarpus (Lecythidaceae), Pterygota macrocarpa, Triplochiton scleroxylon (Sterculiaceae), Pycnanthus angolensis (Myristicaceae) and Tabernaemontana crassa (Apocynaceae). Nigerian-Cameroonian Swamp Forest These forests are found, for example, throughout the Zaire basin along rivers, and in river basins and creeks and there are extensive stands in the Niger Delta. Many of the trees have special breathing or aerial roots (pneumatophores), and these combined with the unusual architecture of species like Lasiomorpha senegalensis (Araceae), a giant, spiny regionally endemic aroid, and the regionally endemic Ficus vogeliana (Moraceae) with its sinuous buttresses bearing flagelliform infructescens, can give these forests a very strange physiognomy. Other common trees include various endemic species like Anthonotha macrophylla, Aphanocalyx hedinii, Gilbertiodendron demonstrans (Fabaceae), Berlinia auriculata, Plagiosiphon multijugus (Fabaceae), Cola hypochrysea (Sterculiaceae), Diospyros gracilescens (Ebenaceae), Neolemonniera batesii (Sapotaceae), Pachypodanthium barteri (Annonaceae), Spondianththus preussii, Uapaca heudelottii Copyright © 2010 Peter Martin Rhind (Euphorbiaceae) and a multitude of regionally endemic species. The tallest trees can reach heights of 45 m, while the dense shrub layer includes various narrow leaved rheophytic species such as the endemic Alsodeiopsis zenkeri (Icacinaceae). There are also many lianas, and climbing palms such as Acistraphyllum, Calamus and Eremospatha with their ‘evil’ hooked spines are particularly characteristic. Nigerian-Cameroonian Lower Montane Forest These forests occur in upland areas such as the Nkolmedjabambon, Ongongo and Nkolebengue hills and on Mount Cameroon. They typically occur above an altitude of about 1800 m and have a more open and irregular structure than lowland forests. On Mount Cameroon the more closed areas have two discontinuous tree layers. The highest can reach heights of 40 m or so and comprise just three species: Schefflera abyssinica and the endemic or near endemic Schefflera manni (Araliaceae) and Syzygium staudtii (Myrtaceae). The second storey reaches heights of about 18 m and includes Canthium glabriflorum, Pittosporum mannii, Pygeum africanum, and the endemic Allophylus bullatus (Sapindaceae). Other endemic trees include Afrostyrax lepidophyllus (Huaceae), Dacryodes macrophylla (Burseraceae), Garcinia mannii (Hypericaceae), Leonardoxa africana (Fabaceae), and a variety of regionally endemic species like Anisophyllea polyneura (Anisophylleaceae), Endodesmia calophylloides (Hypericaceae), Fillaeopsis discophora (Fabaceae) and Protomegabarica stapfiana (Euphorbiaceae). Many of the trees are evergreen but unlike their lowland counterparts they tend to have hemispherical crowns and short gnarled trunks, while plank buttresses are absent. They also lack the cauliflory habitat of lowland species. The two Schefflera species start their life histories, as epiphytes but eventually become stranglers like some Ficus species. The undergrowth is very rich in species but extremely varied in structure. Shrubs can reach heights of 4 m and typically includes Crassocephalus mannii, Discopodium pinninervium, Maesa lanceolata, Solanum mauritianum and the endemic Pavetta hookeriana (Rubiaceae). Also conspicuous are the two giant acantheceous herbs Mimulopsis solmsii and the endemic Oreacanthus mannii (Acanthaceae). In fact, much of the undergrowth is dominated by these two species and few others can tolerate the shade beneath them. In less shady areas, the field layer is characterized by dicotyledonous species especially small members of the Acanthaceae such as the endemic Isoglossum glandulifera (family?), while other endemics include Cyperus mannii (Cyperaceae), Palisota mannii (Commelinaceae) and Senecio burtonii (Asteraceae). There is also an abundance of stinging Urticaceae such as Fleurya ovalifolia and Laportea alatipes, and ferns such as the endemic or near endemic Pteris togoensis (Pteridaceae). Bryophytes are also well represented. Climbing plants, such as the endemic Mikaniopsis maitlandii (Asteraceae), are numerous but not a conspicuous feature of the vegetation. Most are slender twiners or root climbers and the only true liana is Clematis simensis, although certain other species like the endemic Urera cameroonensis (Urticaceae) approach the size of lianas. Epiphytes are very abundant and include flowering plants, ferns, lycopods and bryophytes. Among the flowering plants are Pleopeltis preussii and the endemic Polystachya alpina (Orchidaceae). Nigerian-Cameroonian Upper Montane Forest At elevations between 2000-2900 m on Mount Cameroon there are patches of stunted, open forest with trees reaching no more than about 6 m high. The main trees are Hypericum lanceolatum, Myrica arborea and the endemic Agauria salicifolia (Ericaceae), while common shrubs are Adenocarpus mannii and Philippia mannii. A dense sward of tussock grass dominates the field layer with species such as Andropogon distachys and Bromus leptocladus. Also here are various large forbs like the endemic Peucedanum angustisectum (Apiaceae) and Succisa trichotocephala (Dipsacaceae), while smaller forbs include the endemic Wurmbea tenuis (Colchicaceae). Copyright © 2010 Peter Martin Rhind Nigerian-Cameroonian Mountain Scrub Between mountain forest and mountain grasslands there is a zone of fringing scrub. On Mount Cameroon the characteristic species of this zone include Philippa mannii and the endemic Satureja robusta (Lamiaceae). Field layer plants include various herbs and grasses, but also characteristic of this zone is the giant endemic Lobelia columnaris (Campanulaceae). This species represents West Africa’s nearest approach to the spectacular giant lobelias of the afro-montane floras of East African Nigerian-Cameroonian Mountain Grassland On Mount Cameroon’s upper escarpments and summit areas at altitudes ranging from 3500-3960 m mountain grasslands predominate. In the coarse lava fragments and ash zones on the summit where sulphurous fumes discharge from various fissures the endemic grass Pentaschistis mannii (Poaceae) forms widely spaced tussocks. All other plants are dwarfed to just a few cm including the shrubbly ericoids Blaeria mannii and Philippa mannii. At lower levels where conditions are less harsh the endemic Deschampsia mildbraedii (Poaceae) becomes the main grass species, which in places can exceed 30 cm in height. Other common species are Luzula campestris, Senecio clarenceanus and the endemic Helichrysum mannii (Astaeraceae) and Veronica mannii (Scrophulariaceae). However, on very steep slopes Bulbostylis erratica and Festuca abyssinica becomes a feature of the vegetation together with the endemic Silene biafra (Caryophyllaceae). These upland grasslands have been likened to the paramos of the tropical Andes. However, the tree-like Dendrosenecio and Lobelia species so characteristic of the East African mountains such as Ruwenzory are lacking. Only Crassocephalum