This formation ranges from the coast near the S. Tomé airport to the Praia das Conchas (Seashell Beach), where rainfall is less than 700mm a year (sometimes 500mm a year).
Soils are dark or black with rock outcropping and compact undersoil, supporting grassland and shrubland-type vegetation.
Three kinds of poaceae dominate the regions (Panicum maximum, Rottoboelia esaltata and………….). Small arboreal formations punctuate the herbal mosaic (dry, open tropical forest) which, given the absence of a continuous arboreal canopy, are in strong contrast to the rest of the country.
Especially noteworthy are the Adansonia digitata (Micondoeiro), alternating with Tamarindus indica (tamarindeiro), Ziziphus abissinica (zimbroeiro), Ximenia americana (limoeiro da praia), Psidium guajava (goiabeira), Vernonia amygdalina (“libô mucambú”) and Erythroxyllum emarginatum.
There are also clusters of halophyles (Rhizophora racemosa and Avicennia germinans) on the briny mud of river estuaries and waterlines.
Where salinity is less, there can be found Hibiscus tiliaceus, Dalbergia ecastaphyllum and Erythroxyllum emarginatum.
It is believed that these formations result from massive anthropic pressure: intensive deforestation and frequent recourse to fire, in order to prepare for sugarcane cultivation, since the beginning of Portuguese settlement.
On Príncipe island there are no savannas, although some herbaceous species can be found near the airport.
2.7.7 Shade forest
This formation occupies about 32 289ha, roughly 32,9% of national territory. It tends to occupy areas where relief is smoother and a few hills, such as Muquinquim and Saccli, located on the district of Lobata, and others that do not stand above 300m in height.
This shade forest was created to serve the needs of cocoa (Theobroma cacao) and coffee (Coffea sp.) plantations, species that were introduced with exports in mind; the fixation of nitrogen in the soil allowed for the introduction of Erythrina sp. into these forests.
Cocoa plantations require maintenance of the forest canopy in order to provide shade for cocoa and coffee plants. It’s been demonstrated that this practice helps maintain high levels of forest biodiversity in producing countries (Rice & Greenberg 2000).
2.7.8 Secondary forest (capoeira)
Occupies nearly 30% of the country’s surface. On S. Tomé Island, it covers about 26,000ha and, on Príncipe, about 4,000ha.
There are secondary formations of variable age where we may still identify traces of former use, namely on account of a significant proportion of introduced species. Composition is similar to that of the shade forest, the main distinguishing factor is the presence or absence of coffee or cocoa plants. These areas have, in the past, been used for plantation and are now abandoned, as the soil is marginally apt, at best, slopes are steep and access is difficult.
The flora presents exotic, cultivated and pioneer species, of rapid growth. These form plant communities. Examples are Bambusa vulgaris (Bamboo), Cecropia peltata (Gofe), Maesa lanceolata (Mutopa), Dracaena arborea (Pau Sabão), Ficus spp., (Figtrees), Harungana madagascariensis (Pau sangue), Cestrum laevigatum (Coedano) and more.
Other arboreal species are to be observed here, such as Pycnanthus angolensis (Pau-caixão), Pentaclethra macrophylla (Muandim), Artocarpus altilis (Fruta pão), Artocarpus heterophylla (Jaqueira), Treculia africana (Izanquenteiro), Antiaris welwitschii (Amoreira), Chytranthus mannii (Pessegueiro-de-S. Tomé), among others.
The most frequent vines are: lutchiga (Urera trinervis), Dioscorea spp. and Adenia lobata.
2.7.9 Dry forest
Occupies boundary áreas of Guadalupe, including the margins of Água Castelo, Água de Guadalupe and Rio de Ouro, occurring in the areas where rainfall is between 1000mm and 1500mm per year, with a clearcut dry period. On Príncipe island, there are no dry forests.
On the upper layer of this formation there are deciduous trees like Milicia excelsa, Spondias microcarpa (guêgue) and Ficus mucuso (Figo plocô). The underbrush presents shrubs often threatened by fire, like Ophiobotrys zenkeri (Stala-stala), Oncoba spinosa (malimboque) and Ochna membranacea (pau dumo), Harungana madagascariensis (Pau sangue), Cestrum laevigatum (Coedano), and more.
On S.Tomé, along the estuaries and riverbeds (the most important being Malanza), and on Príncipe (between Praia Grande and Praia Seca), there are halophyle forests occupying the low, flat shores, also seen around murky, shallow lagoons, separated from dry land at the estuaries. The formation occupies a transitional area between marine and land ecosystems. The vegetation, not very diverse, is dominated by: Rhizophora mangle, Rhizophora racemosa (Rhizophoraceae), both of them trees with aerial roots and Avicennia germinans (Avicenniaceae), which possess pneumatophores. The ecosystem may present ferns of the genera Microsorium and Acrostichum aureum, the latter being frequent in mangroves around the world.
On intertidal zones, animal life develops among tree roots. These surfaces host invertebrates such as cf. Isognom and the mangrove crab cf. Aratus, as well as cucumbas of the genus Perioptalmos, fish that can breath outside water as well as in.
Avian species include waterfowl (Gallinula chloropus), cranes (Bubulcus ibis), green-backed herons (Butorides striatus) and the kingfisher (Alcedo spp.).