In 1972, four aerial censuses were carried out to assess the annual migration of zebra and wildebeest between Tarangire National Park and Simanjiro Plains. About 6000 zebra and 10,000 wildebeest were in the Plains in the middle of the rainy season, in April. During the dry season in August the animals were concentrated in the Park. The migration from the Park to the Plains started at beginning of the rains, in November/December. Recent censuses by Tanzania Wildlife Conservation Monitoring (TWCM, 1991, 1995) indicate that an estimated 23,000 zebra and 11,000 wildebeest migrate into the Park from Simanjiro and other wet season areas. Encroaching cultivation is a threat to the migration corridors and sustainability of the ecosystem . Providing benefits from wildlife to communities around the park would safeguard the future of the wildlife.

Summary A total of twenty‐four aerial censuses were carried out in the Simanjiro Plains, northern Tanzania, from 1970 to 1972 in order to estimate the populations, densities and biomass of eleven common large herbivores. Results show that amongst wild herbivores zebra and wildebeest have the highest populations which reach a peak during the wet season between March and May. They were estimated to be about 6000 and 5000, respectively. The corresponding densities were 10.96/km2 and 7.44/km2, respectively. There were practically none of these species in the area during the dry season. Figures for the other species are given. Cattle have the highest population which reaches a peak during the dry season. It was estimated to be about 26,000 with a corresponding density of 44.83/km2. The average total biomass density for all herbivores was 8500 kg/km2. RÉSUMEÉ Un total de 24 recencements atriens furent menés dans les Plaines du Simanjiro, en Tanzanie du Nord entre 1970 et 1972, en vue d'estimer les densités et biomasses des populations de 11 grands herbivores communs. Les résultats montrent que, parmi les herbivores, le zèbre et le gnou ont les populations les plus élvées, qui atteignent un maximum durant la saison des pluies entre mars et mai. On a estimé ces populations à 6000 et 5000 respectivement. Les densités correspondantes sont de 10,96/km2 et de 7,44/km2 respectivement. 11 n' y a pratiquement aucune de ces espéces dans la région durant la saison sèche. Les résultats concernant les autres espèces sont donnés. C'est le bétail qui a la plus haute densité de population, atteignant un maximum pendant la saison séche. II a été estiméà environ 26.000, correspondant à une densité de 44,83/km2. La biomasse moyenne totale pour tous les herbivores est de 8500 kg/km2.

SummaryIn a general ecological study of the Simanjiro Plains, northern Tanzania carried out from 1970 to 1972, the vegetation was studied as part of the habitat of large herbivores using this area. The main vegetation types are short Digitaria macroblephara and Panicum coloratum grassland covering 51%, Acacia tortillis and Commiphora schimperi woodland occupying 26%; the Acacia stuhlmannii and A. drepanolobium bushland occupying 13% and the Pennisetum mezianum and Acacia stuhlmannii (seasonally water‐logged) bushed grassland occupying 10%. Low grass cover (46%) and widespread occurrence of unpalatable or even poisonous species is an indication of overgrazing. For a full list see the appendix.RésuméDans le cadre de I'étude écologique des plaines de Simanjiro (Nord Tanzanie), réalisée de 1970 à 1972, le végétation a étéétudiée en tant que composante de l'habitat des grands herbivores de la zone. Les principaux types de végétation sont une prairie àDigitaria macroblephara et Panicum coloratum qui couvre 51 % de la surface d'étude; une savane boiste àAcacia tortilis et Commiphora schimperi pour 26%; une savane arbustive àAcacia stuhlmannii et A. drepanolobium pour 13%, et la prairie emboissonée et temporairement engorgée àPennisetum mezianum et Acacia stuhlmannii pour 10%. Un couvert herbacé faible (46%) et l'existence frtéuente d'espéces refusées par les animaux ou même toxiques sont des preuves de surpâturage. Une liste de plantes usuelles collectées au cours de l'étude est fournie en annexe.

Trials were conducted in 1987 and 1988 to test methods of intercropping annual Ethiopian clovers, Trifolium spp, with wheat. Several different clover varieties, sowing methods, plant spacings, planting dates and rates of phosphorus application were compared. Planting in single or double alternative rows 20 cm apart did not affect wheat grain and straw yield but broadcast sowing of Trifolium in wheat rows 20 cm apart reduced wheat yield. The Trifolium species used significantly affected legume yield. Phosphorus fertilizer increased yield significantly, especially that of the legume component. The trials indicated that the intercropping of Ethiopian clovers in wheat has potential under African highland conditions. Siembra simultanea de Mgo/Trifolium en Etiopia

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