Climate response of tree growth in Ethiopia along an altitudinal transect and implications on local climate and regional atmospheric circulation dynamics

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With the following extension proposal we intend to finalize ongoing studies on the seasonal growth dynamics of native and exotic tree species in the tropical mountain forest of Munessa, Ethiopia. High-resolution dendrometer measurements of stem diameter variations indicated different growth dynamics of evergreen conifer species (Pinus radiata, Podocarpus falcatus) und evergreen and deciduous broadleved tree species (Prunus africana, Celtis africana), respectively. Trees released from competition showed a strong stimulation of stem growth. The knowledge about seasonal wood formation and growth dynamics form the basis for the interpretation of long tree-ring series of ring width and latewood density and of the analysis of annual variations of stable isotopes of 13C and 18O in wood cellulose. Chronologies of stable isotopes of ca. 400 year-old Podocarpus-trees shall be used for the reconstruction of past variations of precipitation. In combination with an extensive tree-ring network from Asia, they shall further be used to analyse variations in the variability of the summer monsoon variability over the Indian Ocean. Furthermore, stable 13C analyses shall provide information on the physiological reaction of the studied tree species (changes of the ‚water use efficiency‘) on extreme drought events, which provides important information for the development of sustainable forest management options under climate change scenarious of increased rainfall variability.