Are the isotopic composition of cellulose of Fitzroya cupressoides and Nothofagus pumilio promising proxies for paleoclimate reconstructions?

LAVERGNE, A; DAUX, V.; VILLALBA R.; PIERRE, M.; STIEVENARD, M.; SRUR A.M.

Mendoza

Conferencia; Ameridendro 2016 Third American Dendrochronology Conference; 2016

TheSouthern Hemisphere (SH); and particularly southern South America,are under-represented in global climate reconstructions, due to alack of robust paleoclimatic data. Here, we study the isotopicrecords from tree-rings of two native species of northern Patagonia(Fitzroyacupressoides andNothofaguspumilio)to determine their potential as paleoclimatic tracers. Five annuallyresolved tree-ring δ18Oand δ13Cchronologies were developed for calibration study. Over the common60-years long interval, the δ18Oand δ13Cchronologiesexhibit a strong inter-species common signal as indicatedby the significant inter-correlations (r = 0.61 for δ18Oand r = 0.67 for δ13C,p < 0.05) and the high percentage of the total variance explainedby the first Empirical Orthogonal Function (65% for δ18Oand 51% for δ13C).Our results show that δ18Ocellulose of N.pumilio canbe used as a tracer of temperature variations over December-May (r =0.57, p < 0.05); while the cellulose δ13Cof both species records austral summer (December to February)temperature variations (r = 0.69 and r = 0.78, p < 0.05,respectively). The isotopic chronologies contain a regionaltemperature signal representative of a large area south of 38°S,under the influence of the Southern Annular Mode (SAM). As theirvariations are strongly linked to temperature, the isotopic tools canbe used to reconstruct chronologies of temperature but also ofclimate mode such as SAM. Given the longevity of F.cupressoides (morethan 3600 years); this species is comparatively the most interestingto trace these variations in southern South America over the lastthousands of years.