Climate Signals in Oxygen Isotopic Tree-ring Chronologies of Polylepis tarapacana from the South American Altiplano

MILAGROS RODRIGUEZ CATÓN; LAIA ANDREU-HAYLES; MARIANO S. MORALES; CHRISTIE, D; ALVAREZ, CLAUDIO; CAROLINE LELAND; RAO, MUKUND; ROSE OELKERS; DAUX, VALÉRIE; RICARDO VILLALBA

Conferencia; AGU Fall Meeting 2019; 2019

Trees of Polylepis tarapacana (queñoa) are the highest elevation tree-ring archive worldwide, reaching elevations as high as 5200 m a.s.l. An extensive network of P. tarapacana ring-width (RW) chronologies, ranging from 16-22ºS and 67-69ºW in the South American Altiplano, has been used to reconstruct precipitation and drought variability for the last 700 years. The models of these reconstructions rely on the positive relationships between RW variations and previous growing season precipitation. In contrast, RW correlations with the current growing season precipitation are negative. This bimodal pattern is also observed between RW and temperature, but inverse to the precipitation-growth response, with positive and negative correlations for current and prior growing season, respectively. Here we measured stable oxygen (δ 18 O) and carbon (δ 13 C) isotopic composition of tree-ring cellulose from P. tarapacana for the period 1950-2015 to better understand this tree species response to climate variability . We generated isotopic tree-ring chronologies for four sites located along a 500km latitudinal gradient from 18 to 22 ºS . The δ18O records show consistent positive (negative) response with temperature (precipitation) for both, the previous and the current growing season. Rainfall in the Altiplano is related to the South American Summer Monsoon that is more intense during the austral summer (December to March) Accordingly, the highest correlations between δ18O and precipitation were found from January to March and were negative, reflecting more depleted δ18O values during intense monsoon years, as has been described with other paleo records. The positive response found with current growing season temperature spans longer than precipitation from October to April. These results demonstrate a coherent isotope response to climatic variations in both previous and current growing seasons in comparison with the complex relationships observed between RW and climate. Future comparisons between the climate signal recorded by the tree-ring proxies RW, δ18O and δ13C generated at these four sites, located along an aridity gradient, will provide insights on the physiological mechanisms associated with P. tarapacana climate sensitivity .