PhD Project

Stable Isotopes and Plant Water Relations in the Acacia Savanna Woodlands of Ethiopia: Implications for Reforestation and paleoclimatic Reconstructions

The savanna woodlands, which were estimated to cover 30% of the total land area of Ethiopia, are inhabited by economically, environmentally and socially valuable plant and animal species. However, vast areas of the vegetation are being destroyed due to anthropogenic interferences. The effect of land degradation and deforestation are compounded by recurrent droughts. How to restore biodiversity over large areas of degraded lands is a major challenge faced in Ethiopia today. In many cases, natural recovery is either unlikely or slow because the degraded sites have become subject to further disturbances such as over grazing or cultivation. Reforestation/ afforestation is often seen as the most sound rehabilitation technique. However, lack of knowledge, on site - species matching (exotic species), led to failure of most of the attempted reforestation programs and lack of information on the ecology and ecophysiology of indigenous species limited their use in reforestation projects. It is clear that tree establishment in arid and semi arid regions is even more challenging. Despite prevailing harsh environmental conditions, however, naturally occurring tree and shrub species in the savannas have survived with the help of adaptive traits which they have acquired due to long term exposure to ecological stress. Therefore, this study was based on the following questions i.e., i) could these adaptive traits be identified and manipulated to provide a basis for selecting important tree species suitable for rehabilitation/ reforestation of degraded lands? ii) Do some of these species compete favorably for scarce resources and grow well in mixed communities? iii) To what extent does land degradation as a result of natural or anthropogenic interferences disrupts ecophysiological stability and leads to poor adaptations? iv) To what extent does climate (recurrent droughts) affect plant growth and do these effects reflected on tree rings? In an attempt to address the above stated questions and make recommendations for future directions with regard to the restoration of the savanna woodlands, the study comprise three major themes 1) To compare the dominant tree and shrub species for their adaptation to water and osmotic stress, using plant internal water potential and osmotic potential measurements in arid and semi arid conditions and to determine the effect of land degradation on these adaptations. 2. To analyze the presence of annual tree rings and understand tree growth dynamics of naturally co-occurring tree species, and evaluate the relationship between long term radial growth and climatic parameters, and evaluate the association of ENSO and drought years in Ethiopia with tree ring pointer years. 3. To explore whether there is a common pattern in stable carbon isotopes in tree rings of co-occurring tree species and determine the climatic content and strength of the stable carbon isotopes signal as a potential climate proxies.


Advisors:

Prof. Dr. R. Mitlöhner (Institute of Silviculture/Dept. of Tropical Silviculture, University of Göttingen)

PD Dr. M. Worbes (Dept. of Tropical Agronomy, Institute of Agronomy and Animal Production in the Tropics and Subtropics, University of Göttingen)

Dr. Demel Teketay (Forest Stewardship Council African Regional Office, P.O.Box UP 805, Kumasi, Ghana)