Combining dendrochronology and matrix modelling in demographic studies: An evaluation for Juniperus procera in Ethiopia

Tree demography was analysed by applying dendrochronological techniques and matrix modelling on a static data set of Juniperus procera populations of Ethiopian dry highland forests. Six permanent sample plots were established for an inventory of diameters and 11 stem discs were collected for dendrochronological analysis. J. procera was proved to form concentric annual growth layers in response to seasonal changes in precipitation. Uncertainty analysis for the matrix model revealed its robustness to variations in parameter estimates. The major outcome was that the population growth rate is very sensitive to changes in growth or survival of trees between 10 and 40 cm DBH. For forest management this implies that these intermediate sized individuals should be protected and less used for harvest. This study documents that interesting results can be achieved using a relatively simple approach that can easily be adopted for other areas or with other species. However, the matrix modelling requires more precise knowledge about the trees' fecundity and survival (especially for the smaller individuals) and more consistent inventories. For tree-ring analysis it can be concluded that J. procera from Ethiopia has potential to investigate the relationship between tree growth and precipitation with a high temporal resolution.