Which matters most for the formation of intra-annual density fluctuations in Pinus pinaster: age or size?
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A new method is pro posed to standardize chronologies of intra-annual density fluctuations to improve their intra-annual climatic signal.
In the Mediterranean area, intra-annual density fluctuations (IADFs) are triggered by short-term climatic variations during the growing season. It is known that the formation of these anatomical structures is dependent on age and size, which can represent a problem during the extraction of the environmental signal from IADF chronologies. We present a new method using a two-step approach to remove the effect of tree-ring width from IADF chronologies. The climatic signal of IADF chronologies obtained by the proposed method was compared with previous methods, using 160 Pinus pinaster tree cores from an even-aged stand on the west coast of Portugal. Our results show that the climatic signal of IADF chronologies was strongly affected by the standardization method used, and that it could be improved by removing the effect of the predisposing factors (cambial age and tree-ring width) on IADF formation. Moreover, additional climatic information (previous winter precipitation) was only revealed when the effect of tree-ring width was removed from IADF series. Finally, we propose that this new method should be tested for other species and across larger geographical areas to confirm its capacity to remove noise from IADF chronologies and to improve their intra-annual climatic signal.
KeywordsEcological wood anatomy Intra-annual density fluctuation Maritime pine Mediterranean climate Standardization
Author contribution statement
FC: writing the paper and analyzing the data. FC and JV: field and laboratory work. JV, GB, MdL, CN, HF and PC: reviewing the paper. CN: coordinating the research project.
This study was supported by the Fundação para a Ciência e a Tecnologia, Ministério da Educação e Ciência (FCT) co-financed by Compete, through the project PTDC/AAC-AMB/111675/2009. Filipe Campelo was supported by a postdoctoral research grant (SFRH/BPD/47822/2008) from FCT with funds from POPH (Portuguese Operational Human Potential Program) and QREN Portugal (Portuguese National Strategic Reference Framework). Martin de Luis was funded by Spanish Ministry of Education and Science co-funded by FEDER program (CGL2012-31668). This study was conducted in the frame of the COST Action STReESS (FP1106). The authors thank the communicating editor and two anonymous reviewers for helpful comments and suggestions on an earlier version of the manuscript.
Conflict of interest
The authors declare no conflict of interest.
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