Earlywood vessels of the sub-Mediterranean oak Quercus pyrenaica have greater plasticity and sensitivity than those of the temperate Q. petraea at the Atlantic–Mediterranean boundary

Abstract

Earlywood vessel features indicate different adaptations of Quercus petraea and Q. pyrenaica , which are probably related with their corresponding Atlantic and sub-Mediterranean ecological requirements. We studied the climatic signal of the earlywood anatomy of a temperate [Quercus petraea (Mattuschka) Liebl.] and a sub-Mediterranean (Quercus pyrenaica Willd.) oak species growing under similar climatic conditions in a transitional area between the Atlantic and Mediterranean regions of the Iberian Peninsula. We hypothesized that both species react differently in their wood anatomy due to their contrasting ecological requirements, and we test the usefulness of earlywood anatomical features to study the behaviour of these ring-porous oaks upon climate. For this, we measured the earlywood vessels, and obtained annual series of several anatomical variables for the period 1937–2006 using dendrochronological techniques, considering whether the vessels belonged to the first row or not. After optimizing the data set by principal component analysis and progressive filtering of large vessels, we selected maximum vessel area and total number of vessels as they resulted to be the optimal variables to describe vessel size and number, respectively. Vessel size of Q. pyrenaica was dependent on precipitation along the previous growing season, whereas it did not show any clear climatic response for Q. petraea. On the contrary, vessel number was related to winter temperature for both species. These relationships observed between climate and anatomy appeared to be stable through time. The results obtained reinforce the utility of earlywood vessel features as potential climate proxies.