Comparisons of the Performance of δ13C and δ18O of Fagus sylvatica, Pinus sylvestris, and Quercus 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 intertrees and interspecies variations over 1960-2007 of oxygen and carbon isotopic compositions in ring cellulose of Fagus sylvatica, Pinus sylvestris, and Quercus 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 higher in pine 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 delta O-18 and delta C-13 chronologies were significantly correlated to one another in the three species and responded primarily to air moisture and T-max, 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 delta O-18, and to a lesser extent delta C-13, from the three different species are reliable proxies for reconstructing past hydroclimatic variations in Europe.