Climate change inferences from tree rings in the Mediterranean area: a database for Portugal.
Coordinator - Cristina Nabais
Programme - POCI/CLI/58680/2004
Execution dates - 2005-10-01 - 2008-10-01 (36 Months)
Funding Entity - Fundação para a Ciência e Tecnologia
Total Funding - 50 000 €
Proponent Institution -
Participating Institutions
Departamento de Botânica, FCTUC

Instituto Superior de Agronomia, UNL
The analysis of how forest ecosystems may react under scenarios involving changing climatic conditions is of major importance. Tree rings can be used as proxies to understand how forests have reacted to past climatic and anthropogenic events and trends. In terms of current and future climate investigations, research should foster closer ties between the dendrochronological and climate modelling communities. Dendrochronology-based information has value for fundamental understanding of various processes relevant to climate, as well as providing empirical data to numerical climate models. Regarding the improvement of the data set, special emphasis has been placed recently on broad geographical distributions of dendrochronological series, because detailed spatial reconstructions require suitable networks of tree-ring chronologies from all over the world. Specific regional field studies, including transects, would enable dendrochronology to establish a link with regional climate models, whose simulations often suffer from a lack of adequate information at the appropriate spatial scales for initialisation and verification purposes. In Mediterranean regions, studies of tree rings are scarce, despite their potential for understanding and predicting the effects of global change on important ecological processes such as desertification. Summer drought is the most important ecological factor influencing vegetation in Mediterranean ecosystems. Vegetative activity does not always and everywhere have a regular dormancy period, so that annual tree rings are not always formed. It is best to consider the summer period as a period of ‘drought-imposed rest’ rather than true dormancy. The main objective of this project is to construct a dendrochronological database for Portugal and use tree rings as proxies to climate reconstruction in the Mediterranean area. The target species of the project are: Pinus pinaster, Pinus pinea, Quercus robur and Quercus suber. Ring-width measurements and intra-anual wood density fluctuations will be analysed in all these tree species. Stable carbon and oxygen isotopes will be analysed in Pinus pinaster. In relation to wood growth, only very limited information is available for Q. suber, partly resulting from the difficulties in distinguishing annual rings in the trees under sustained cork production. The possibility of correspondence between macroscopic and microscopic properties can be helpful in the interpretation of rings and the identification of the signs of climatic fluctuations in Q. suber.