Seasonal growth dynamics of different tree species in Munessa Forest, Ethiopia and their climatic control

Knowing seasonal tree growth dynamics in tropic al regions is the prerequisite for understanding annual wood formation, which is a basic parameter for many applications in forest ecology and management and dendrochronological studies. In Ethi opia, some tree species exhibit a variable wood anatomy due to regional differences in seasonal rainfall patterns (Wils et al. 2009). Hence, trees of the same species (e.g. Juniperus procera , Cupressaceae) may show clearly distinct ring boundaries or faint to indistinct ring boundaries including many wood anatomical anomalies like wedging rings and multiple rings, causing seriou s constraints for cross-dating (Wils and Eshetu 2007, Wils et al. 2009, Sass-Klaassen et al. 2008). Nevertheless, under suitable climatic conditions it may be possible to cross-date samples within a site and to construct chronologies that are correlated among each other and with climate variables (Couralet et al. 2005, 2007, Sass- Klaassen et al. 2008). Acacia species from the Ethiopian savanna lowlands have been successfully used for dendroclimatological studies (Eshete & Ståhl 1999, Gebrekirstos 2006, Gebrekirstos et al. 2008). However, the seasonal growth characteristics of Ethiopian tree species are so far unknown (Sass-Klaassen et al. 2008). Thus, our aim is to record cambial growth dynamics and seasonal variations of wood formation in relation to climate forcing to provide a basis for the interpretation of wood anatomical structures and tree-ring formation in the Ethiopian highland forests.