Grasslands of the World.pdf - Disasters and Conflicts - UNEP

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Plate 11.2
Millet, a major crop in the arid and semi -arid areas.
Grasslands of the world
soils; crops are only possible under special conditions; stock-rearing, where it is
possible, reigns without competition . Detailed descriptions are available in the
pasture profiles for Burkina Faso (Kagoné, 2002), Mali (Coulibally, 2003) Niger
(Geesing and Djibo, 2002) and Ghana (Oppong-Anane, 2001).
The Sahelian zone , from the Atlantic through Chad , is arid , with a summer
rainfall of 250–500 mm and a dry season of nine to eleven months. In the
northern Sahel , which belongs to the Saharan-Sindian floristic domain according
to Wickens (1997), the 150 mm isohyet corresponds to the southern limit of
the Saharan species Cornulaca monacantha , Panicum turgidum and Stipagrostis
pungens and to the northern limit of such Sahelian shrubs as Boscia senegalensis
and Commiphora africana and the grass Cenchrus biflorus .
The Sahel ’s southern limit adjoins the deciduous woodlands of the Sudanian
domain at between 450 and 500 mm/yr precipitation . Acacia spp. dominate the
thin scrub along with Balanites aegyptiaca ; laterite outcrops and cuirasses are
colonized by Combretum nigricans , Guiera senegalensis , Lannea acida and
Sclerocarya birrea . The grass component of the northern dunes is dominated
by Cenchrus biflorus , Aristida mutabilis and Schoenfeldia gracilis . To the south,
Schoenfeldia gracilis is important; on flood plains of rivers, grasslands with perennials
like Echinochloa stagnina , Oryza barthii and Vossia cuspidata provide
excellent grazing when the floods have receded. Crops are grown, opportunistically,
with millet (Pennisetum spp. ) the most important – it is usually sown
when rain falls, with resowing, perhaps several times, until a reasonable stand
is attained.
MARZIO MARZOT