Epsilon Archive for Student Projects

Abstract

A short study was made on the regeneration and distribution of the Baobab tree, Adansonia digitata, in Kondoa Irangi Hills, Tanzania. About 300 individuals were mapped and measured in areas with different vegetation and land management, to try to find out what environmental factors influence population structure, the growth, regeneration and survival. Core samples were taken to calculate growth rates for different size classes, and to see if they correlate to rainfall data. Seed germination tests were carried out to simulate what the seeds may be exposed to naturally, e.g. fire, animal digestion or the common practice of making an alcoholic brew from the Baobab seed. Baobab population densities and regeneration were significantly higher in areas dominated by cultivated fields than in other areas. This was suggested to be due to protection against fire and grazing animals. Young Baobab individuals, ca. 20-70 years old, had a significantly higher growth rate (annual radial increase) than older individuals. This means that a population may hold fewer individuals in small size classes, and still be constant over time. An estimation of the age distribution, however, suggests a period of very low regeneration rates some 60-110 years ago, and that more recent regeneration is not sufficient to keep the population from declining. The germination tests showed that the seeds do not need any special treatment to break seed dormancy, soaking for three days in cold water is enough.