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Revista chilena de historia natural

Print version ISSN 0716-078X

Abstract

ARAVENA, JUAN C. et al. Tree-ring growth patterns and temperature reconstruction from  Nothofagus pumilio (Fagaceae) forests at the upper tree line of southern Chilean Patagonia. Rev. chil. hist. nat. [online]. 2002, vol.75, n.2, pp.361-376. ISSN 0716-078X.  http://dx.doi.org/10.4067/S0716-078X2002000200008.

Nothofagus pumilio (Poepp. et Endl. Krasser) is a deciduous species that dominates the upper tree line of the Chilean and Argentinean Andes between 35º 36' and 55º 31' S. In this study we describe the development of 21 tree-ring width chronologies of N. pumilio across its southernmost range of distribution (51-55º S) in Chile, and analyze the relationship between N. pumilio tree-growth and climate. Ten of the tree-ring chronologies in our study, show an increasing trend and/or above average tree-ring growth since ca. 1960 to 1996, which coincides with the increase in temperatures shown by instrumental records from southern Patagonia. Another dominant pattern in tree-growth is a remarkable ca. 7-year cycle present in three of the study sites from Isla Navarino, the southernmost of our study areas (ca. 55º S). These two dominant tree-growth patterns, represent the main modes of variation of the N. pumilio tree-ring records in the southern Chilean Patagonia, accounting for 14 and 28 % of its total variance, respectively. Based on the positive correlation between tree growth and temperature in several of the study sites analyzed in this work, we developed a reconstruction of the Punta Arenas minimum annual temperatures from the seven tree-ring records with the highest correlation with temperature, covering the 1829-1996 period. The reconstruction shows that during most of the 19th century, minimum annual temperatures remained below-average and increased to values fluctuating around the mean during the 1900-1960 period, followed by a clear trend with above-average values after 1963

Keywords : dendroclimatology; Nothofagus, tree-rings; tree line; Patagonia; warming trend.

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