Resin tapping in Pinus pinaster: effects on growth and response function to climate

Pinus pinaster is of great ecological and economic importance and has traditionally been subjected to intensive uses such as wood and resin extraction. In the last decade, dendrochronological methods are increasingly being used to analyze the effects of climatic factors on the growth of the maritime pine, although tapped trees were generally avoided because it was thought that their growth was affected by resin extraction. In Spain, however, it is hard to find a long-lived forest of P. pinaster that has not been subjected to tapping for resin. In the present paper, we performed dendrochronological analyses of this species from wood cores and cross sections taken from both resin-tapped trees and resin-untapped trees killed by a fire in 2008 in the central Iberian region. On the one hand, we reconstructed the history of forest management by means of analysis of resin scars in the cross sections of resin-tapped trees. This facet of dendrochronological dating had not heretofore been developed, and little is therefore known about it. We dated 46 scars, which indicate a history of intensive resin extraction in the 1920-1950 period. Moreover, we attempted to answer the question: Have the old resin extractions in P. pinaster precluded the use of their growth rings for dendrochronological and dendroclimatic studies? We found that resin extraction did not alter general short-wavelength variability, and we developed a local chronology with all synchronized series, and the response function with respect to climate is similar to other oldest P. pinaster forests studied in Spain. The information we have recorded can be of use for providing tools to land managers for interpreting forest dynamics in resin-tapped regions.