Frankfurt (Main), Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Frankfurt (Main), Univ., Diss., 2001. / Computerdatei im Fernzugriff.

Hamburg, University, Diss., 2005.

Frankfurt (Main), Universiẗat, Diss., 2001.

Giessen, Universiẗat, Diss., 1999. / Dateiformat: zip, Dateien im PDF-Format.

In the past 15 years, finding fuelwood has become a physical and economic burden to Sahelians inhabiting both rural areas and urban centers. This has led to a poor man's energy crisis, the scope of which is reviewed. Increasing demands on fuelwood have had negative socioeconomic effects. Non-commercial substitutes of fuelwood, though widely used, are not keeping up with demands. Commercial energy sources are not affordable due to their high cost. Overall, it is concluded that the substitute for wood is wood. So far, fuelwood plantation projects in the Sahel have suffered from a noticeable lack of economic and financial analysis. Popular investment decision criteria in forestry management are presented and evaluated. Given a eucalyptus growth function, current market prices, production costs, and interest rates, a model has been developed to solve for the optimal rotation age. The results showed that fuelwood plantations could be financially feasible. Site quality and interest rates are important in determining the size of the optimum criterion as evidenced by the sensitivity analysis performed. The paper surveyed a few econometric studies dealing with wood products. Based on the linear and double-log static models, consumption functions for fuelwood demand projections have been derived for seven countries of the Sahel. Based on these equations and different statistical tests, it was found that population is the single most important factor determining fuelwood consumption in the Sahel. Another significant variable is the woodland area. Income as represented by GNP did not have any effect on fuelwood demand. On the basis of these findings and the overall study, the following measures are recommended: (1) Population control should be implemented as a high priority to help curb the increased and increasing fuelwood demands; (2) More plantations should be undertaken to increase the exhausted supplies. Meanwhile, the management of existing natural forests along with the introduction of affordable fuelwood substitutes should be implemented. (3) More leadership is needed to involve the local people into development projects.

Zugl.: Hohenheim, Univ., Diss., 2001.

The objectives of this dissertation were to identify soil and vegetation changes due to grazing by livestock and to develop guidelines for monitoring the impact of livestock in the Sahelian zone of Africa. The study was conducted in eastern Senegal during 1983 to 1985. The basic methodology was a study of the process of degradation (retrogression) through the collection of data on soils and vegetation along a gradient of increasing livestock pressure. Two gradients were selected along piospheres. Each gradient was placed on a range site that had homogeneous state factors (climate, geology, and rainfall). The results show that the changes in the soil were confined to the top soil horizon. There was a negative correlation between livestock pressure and factors such as infiltration, percent nitrogen, and percent carbon, and a positive correlation between livestock pressure and the factors of bulk density, and phosphorous content. Changes in the vegetation community were dependent on the range site. On the sandy site, there was a linear, negative correlation between livestock pressure and the factors of plant density, plant cover and biomass. On the loamy range site, the changes in these factors along the gradient had a 2nd or 3rd order polynomial relationship. The effects of bush fires and short term droughts on the vegetation were also studied. Drought, in particular, has an impact that is similar to that of livestock pressure, and may compound the results. Multiple regression analysis and a Twinspan ordination program were used to select parameters and plant species that were highly correlated with the gradient, and could act as indicators of each stage of degradation. These indicators can be used to monitor the impact of livestock on rangelands. General parameters, such as total plant density, are less sensitive to drought-induced changes than the composition of indicator species, but the latter are easier to monitor. Both types of indicators can form the basis for a monitoring methodology that can be used in Africa at three management levels: the individual herder, extension agents and regional branches of the division concerned with rangelands, and policy makers at the ministerial level.

University, Diss--Hannover.

Modern African states need to be analyzed from a perspective which complements, corrects, or specifies dependency/world-system and structural marxist explanations of peripheral political dynamics. This dissertation offers such a perspective as it seeks to explain variations in state-society exchange among four comparably dependent modern nations of the Sahelian African region (Senegal, Mauritania, Chad, Sudan). The model accounts for the political ramifications--state's mode of rule, level and type of opposition mobilization--of each country's ethno-religious configuration. It assumes that trans-national economic (and/or geopolitical) dynamics do not necessarily weigh more heavily on the dynamics of state-society relations than local political processes.