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Relationship between the establishment of Nothofagus pumilio in the upper treeline and climate variations in Northern Patagonia
SRUR, A.; VILLALBA, R.; RODRÍGUEZ-CATÓN, M.; AMOROSO, M. M.; MARCOTTI, E.
Conferencia; Third American Dendrochronology Conference_AmeriDendro; 2016
The individuals of one species that grow at the extremes of their geographic distribution, are exposed to more extreme environmental conditions than the rest of the population. These individuals are more sensitive to environmental changes that favor their establishment or accelerate their mortality, and are therefore more sensitive to changes in the distribution of the species. In the present study, the relationship between regional variations in climate and the dynamics of establishment and growth of individuals of Nothofagus pumilioon the upper limit of the forest of north Patagonia was determined. The structure and density of individuals established in the upper limit of the forest was studied, along with the temporal patterns of establishment and radial growth in three sites located along a marked west-east precipitation gradient. The pattern of establishment of N. pumiliowas compared to the regional variations in temperature and precipitation, as well as the indices of atmospheric circulation related to the regional climate, including El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Lastly, we explored the age at which the growth of the individuals recently established, was influenced by the variation in climate. Mesic and dry sites were characterized by a lower density of individuals with a larger diameter at the base, greater height, and larger trunk. A notable increase of establishment starting in the mid 1970´s was registered, as well as a decrease in the late 1990´s in all the sites along the precipitation gradient. The greatest establishment coincides with the increase in temperature of spring-summer and the positive phase of the PDO.