Potential of oak tree-ring chronologies from Southern Portugal for climate reconstructions

The present work reports a first attempt to assemble long tree-ring chronologies from Portugal potentially useful for climate reconstructions. Three oak species (Quercus pyrenaica, Quercus faginea, and Quercus ilex) were sampled at three sites in southern Portugal to obtain tree-ring chronologies. The longest tree ring series covers 173 years extending back to 1840. Our tree-ring records show, depending on the site, moderate-to-high correlations with precipitation in different seasons (from r = 0.40, p < 0.01, to 0.81, p < 0.001) and temporal stability in the growth/climate relationship for two sites. Calibration-verification trials confirm the reliability of climate/growth models for climatic reconstructions back to periods represented by tree-ring records from these two sites. Regional precipitation for Alentejo can be estimated for the following seasons: April through August (calibration r2 = 0.24); September, from previous year, to July (calibration r2 = 0.65). The results are a promising kick-off for Portuguese dendroclimatology, since they represent a significant breakthrough in the Mediterranean region, especially for Iberian Peninsula, where there is a considerable lack of dendroclimatic reconstructions. Further efforts to extend the tree-ring records back in time using subfossil material should be undertaken.