Growth dynamics of Podocarpus falcatus in tropical mountain forest in Ethiopia

The tropical mountain forests in equatorial Africa are threatened by climate change and increasing land use intensity. In Ethiopia, the forest cover decreased during the last century to an alarmingly minimum. Recent remote sensing studies (Dessie & Kleman 2007) revealed a further reduction to 3% forest coverage in the vicinity of our study area due to an increasing population and expansion of agricultural land. On the other hand, additi onal environmental stress is caused by climate variability with a high frequency of drought event s, possibly aggravated by long-term climate change. Therefore, understanding growth reactions and ecological behaviours of indigenous tree species to the changing environmental conditions are of great importance for a sustainable utilization of the remnant natural forest. During recent years, several dendroclimatological studies were conducted in Ethiopia working with different tree species and dealing with various problems. Gebrekirstos (2006) analysed stable isotopes of Acacia species of the savannah woodlands for a paleoclimatic reconstruction and later assessed climate-growth relationships (Gebrek irstos et al. 2008, 2009). Furthermore, wood anatomical investigations of the highland species Juniperus procera showed clear distinct ring boundaries or faint to indistinct ring boundaries including many wood anatomical anomalies like wedging rings, causing serious constraints for cross-dating (Couralet et al. 2005, Sass-Klaassen et al. 2008, Wils et al. 2009). This variable wood anatomy is the result of regional and temporal differences in seasonal rainfall patterns. So far, the dendrochronological potential of the indigenous Podocarpus falcatus was only explored on a species from South Africa. February and Stock (1998) stated that the evergreen conifer tree is not useful for dendrochronological analyses because of its lobate growth and multiple rings. On the other hand, different species of Podocarpaceae (e.g. Podocarpus totara , Podocarpus hallii ) were successfully analysed and crossdated in New Zealand (Bell &Bell 1958, Dunwiddie 1979, Norten et al. 1987). Hence, the objective of our study is to investigate native Podocarpaceae in Ethiopia and check its dendrochronological potential. In this extended abstract we present first results of varying approaches to collect knowledge about the growth dynamics of Podocarpus falcatus .

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