Comparisons of the performance of δ13C and δ18O of F. sylvatica, P. sylvestris and Q. petraea in the record of past climate variations

Climate reconstructions in temperate Europe have been widely based on oak species. However, other co‐occurring species, largely distributed in Europe, may be used for recording climate variability. In this paper, we documented the inter‐trees and inter‐species variations over 1960‐2007 of oxygen and carbon isotopic compositions in ring cellulose of F. sylvatica, P. sylvestris and Q. petraea co‐occurring in the Fontainebleau forest (France). Our results indicated that large levels of series replication (11 trees on average) were required to generate isotopic mean series representative of the populations. We calculated mean isotopic ratios in pine higher than in the deciduous species, and hypothesized that these contrasts resulted from differences in stomatal conductance, phenology and canopy structure, and, for oxygen, also in water uptake depth and isotopic exchange rate. We found that δ18O and δ13C chronologies were significantly correlated to one another in the three species and responded primarily to air moisture and Tmax, which indicated that stomatal conductance was an important driver of changes in both types of records. We determined that the correlations were strong with the May to July climate variables in F. sylvatica, and with the July and August ones in Q. petraea and P. sylvestris. We showed that the oxygen records were systematically more coherent than those of carbon. This study demonstrated that δ18O, and to a lesser extent δ13C, from the three different species are reliable proxies for reconstructing past hydroclimatic variations in Europe