Past Summer Temperatures Inferred From Dendrochronological Records of Fitzroya cupressoides on the Eastern Slope of the Northern Patagonian Andes

Abstract

Estimating summer temperature fluctuations over long timescales in southern South America is essential for better understanding the past climate variations in the Southern Hemisphere. Here we developed robust 212 year long basal area increment (BAI) and δ13C chronologies from living temperature‐sensitive Fitzroya cupressoides on the eastern slope of the northern Patagonian Andes (41°S). After removing the increasing trend from the growth records likely due to the CO2 fertilization effect, we tested the potential to reconstruct past summer temperature variations using BAI and δ13C as predictors. The reconstruction based on δ13C records has the strongest predictive skills and explains as much as 62% of the total variance in instrumental summer temperature (n = 81, p < 0.001). The temperature signal recorded in tree‐ring growth is not substantially different to that present in δ13C and consequently does not provide additional information to improve the regression models. Our δ13C‐based reconstruction shows cold summer temperatures in the second part of the 19th century and in the mid‐20th century followed by a warmer period. Notably, the 20th and the early 21st centuries were warmer (+0.6°C) than the 19th century. Reconstructed summer temperature variations are modulated by low‐latitude (El Niño–Southern Oscillation) and high‐latitude (Southern Annular Mode) climate forcings. Our reconstruction based on δ13C agrees well with previous ring width based temperature reconstructions in the region and comparatively enhances the low‐frequency variations in the records. The present study provides the first reconstruction of summer temperature in South America south of 40°S for the period 1800–2011 entirely based on isotopic records.

Comparisons of the Performance of δ13C and δ18O of Fagus sylvatica, Pinus sylvestris, and Quercus petraea in the Record of Past Climate Variations

“… P. sylvestris , as a gymnosperm, has higher intrinsic water use efficiency (iWUE, i.e., the ratio of photosynthetic carbon uptake ( A ) to stomatal conductance ( g s ); e.g., Leonardi et al, ) than the two deciduous trees. In accordance with this general rule, in this study, the mean values of iWUE of P. sylvestris , F. sylvatica , and Q. petraea are equal to 99.5, 97.2, and 92.5 μmol CO 2 mol −1 H 2 O, respectively (iWUE calculation performed as in Lavergne et al, ). A larger iWUE can result from either reduced g s or increased A (Scheidegger et al, ).…”

From Trees to Ecosystems: Spatiotemporal Scaling of Climatic Impacts on Montane Landscapes Using Dendrochronological, Isotopic, and Remotely Sensed Data

“…As in related studies, we found that wood δ 13 C is positively correlated with temperature, especially in spring-summer, the season of wood formation, and negatively with summer precipitation and soil moisture ( Table 2) (Ferrio & Voltas, 2005;Gagen et al, 2006;Lavergne et al, 2018;Wu et al, 2015). This shows that dry summers (when high temperature and VPD are pervasive) cause water stress in trees, leading to stomatal downregulation of gas exchange (i.e., low g s and C i ) yielding 13 C-rich wood tissue (McCarroll & Loader, 2004).…”

Isotopic Equilibrium Between Precipitation and Water Vapor in Northern Patagonia and Its Consequences on δ18Ocellulose Estimate

“…The investigated site is at the Cerro Perito Moreno ski station. It is located ~80 km south from Lavergne et al's (Lavergne et al, 2016; Lavergne et al, 2017; Lavergne et al, 2018) sampling sites. This site was selected because (1) it is far from lakes and thus likely not affected by local moisture sources and (2) it is surrounded by a forest of Nothofagus pumilio trees and located close to the tree line, presenting similar environmental conditions to those of the sites studied in the aforementioned Lavergne et al's studies.…”

“…This site was selected because (1) it is far from lakes and thus likely not affected by local moisture sources and (2) it is surrounded by a forest of Nothofagus pumilio trees and located close to the tree line, presenting similar environmental conditions to those of the sites studied in the aforementioned Lavergne et al's studies. Practical reasons were also decisive in choosing the site: The ski station is easily accessible by road and it provides a shelter and reliable power supply, facilities not available on Lavergne et al's (Lavergne et al, 2016; Lavergne et al, 2017; Lavergne et al, 2018) sites. In consequence, we were able to test the isotopic equilibrium hypothesis in a similar environment with the same species as those investigated by Lavergne et al (2016; 2017; 2018).…”

“…A number of studies have explored the potential of the width and density of annual tree rings in the Andean mountains of Chile and Argentina to reconstruct past climate variability (e.g., Aravena et al, 2002; Boninsegna et al, 2009; Lara et al, 2005; Mundo et al, 2012; Muñoz et al, 2013; Villalba et al, 1997). Recent studies conducted in the Andean Cordillera between 36°S and 54°S have produced carbon and oxygen series of isotopic composition of tree ring cellulose (δ 13 C and δ 18 O) of various species including Nothofagus pumilio (Grießinger et al, 2018; Lavergne et al, 2016; Lavergne et al, 2017; Tognetti et al, 2014), Austrocedrus chilensis (Roig et al, 2006), Fitzroya cupressoides (Lavergne et al, 2017; Lavergne et al, 2018; Urrutia‐Jalabert et al, 2015), and Araucaria araucana (Arco Molina et al, 2019). They cover at most the last 200 years.…”