Weidepotential und Landdegradierung in den Trockengebieten Kenias, dargsestellt an Testflächen im Samburu-Distrikt

Abstract

The survey and evaluation of the range potential in the semi-arid lands of the Samburu District was carried out with the aid of the combined earth study techniques at four data levels (satellite images of LANDSAT 5, aerial photographs, special photograph survey from low flying aircraft, and ground truth data).Various homogeneous test sites were selected in each of the five main landscape units. The highest biomass production occurs in the grassland dambos as well as on the volcanic plateaus (Marti) with Commiphora-Acacia woodland, dwarf-shrub and perennial grasses. However, both landscape types are mostly avoided by the nomads and their livestock: the dambos because of the low content of palatable grasses and herbs, as well as the dangers connected with cracking and piping features of the vertisols, and with insects and carnivores respectively, the plateaus because of the difficult accessibility and lack of water. The most important rangelands include the foot slopes in front of the Marti with open Commiphora bushland and dwarf-shrub and the adjacent inland plains covered by open Acacia woodland and dwarf-shrub. At the end of the main rainy season the good rangeland sites reach a biomass of 2500 kg/ha. However, two or three weeks later, there is a remarkable decrease in the fodder value. The biomass production of the slopes is often lower than that of the inland plains, because they form favoured sites for settlements and, therefore, suffer from overuse and severe soil erosion. Valley sites with riparian woodland or bushland are often used by goats and camels, while cattle do not find any substantial species in these vegetation types. Due to the high variability of rainfall and the uncertain biomass production, the rangeland of the area in question can only be classified as an area restricted to certain browsing animals, such as goats and camels. However, cattle which are mainly dependent on grasses and herbs, can hardly survive every dry season in the long run and would never gain weight. Consequently a rearrangement of animals adapting to the sensitive ecosystem in these tropical drylands should be considered in useful development planning. Finally, regeneration and anti-erosion measures remain necessary.