Climate-growth relationships of deciduous and evergreen Nothofagus species in Southern Patagonia, Argentina

Abstract

Differences in growth patterns between a deciduous species, Nothofagus pumilio, and an evergreen species, Nothofagus betuloides, were analyzed in Lago del Desierto, southern Patagonia, Argentina (49°01′ S – 72°52′ W). The relationships between the growth rate of these two species and variations in temperature, precipitation, and the Southern Annular Mode (SAM) were also evaluated. We processed and analyzed 54 samples of N. pumilio and 48 of N. betuloides and developed two tree-ring width chronologies covering the periods of 1754-2014 and 1650-2014, respectively. The results from N. betuloides are especially important due to the small number of studies about this species in the area. Results indicate similarities between the tree-ring growth patterns of the two species. However, N. betuloides grew with a slower rate and had shorter periods of growth below average. We suggest that the particular growth pattern of N. betuloides is determined by its higher tolerance to stress situations and evergreen physiological characteristics. Significant correlations were observed between N. pumilio tree-ring growth and temperature from August-October of the previous year, and with the SAM index from December-January of the current year. N. pumilio did not show significant correlations with precipitation. Significant correlations were found between N. betuloides growth and precipitation from December-January of the previous year. As evergreen species have a more conservative response to temperature changes, N. betuloides growth was not significantly affected by temperature or by the SAM index. These results are encouraging and further studies could help improve our understanding of the relationship between the environment and species with different seasonality of foliage growth. Our study provides the first chronologies of N. pumilio and N. betuloides in the area and increases knowledge about the relationships between tree-ring growth and climate.