Developing a tree-ring based precipitation reconstruction from the Southern Bolivian Altiplano since 1200 AD: some preliminary results

MARIANO S. MORALES; DUNCAN A. CHRISTIE; RICARDO VILLALBA; JEANETTE PACAJES; JAIME ARGOLLO

Valdivia

Workshop; Documenting, understanding and projecting changes in the hydrological cycle in the American Cordillera. IAI Collaborative Research Network 2047. Third Science meeting; 2010

Interamerican Institute for Global Change Research (IAI)

Instrumental records of climate in the tropics are short, fragmentary and heterogeneous. Longer records are needed to understand the nature of climate variations, and how the interannual modes of tropical climate variability (such as ENSO) have evolved under changes in long-term background conditions. Polylepis tarapacana (Rosaceae) is a small- to medium-size tree that grows on the slopes of the Andean tropical volcanoes in Bolivia and adjacent areas of Perú, Chile and Argentina (17–23°S) between 4100 and 5200 m a.s.l. Previous dendrochronological studies indicate that the radial growth of P. tarapacana is influenced by precipitation during the summer preceding the ring formation. Based on extensive collections of Polylepis samples across its range of distribution, more than 20 ring width chronologies have recently been developed. In this study, we briefly describe the development and characteristics of a composite chronology of Polylepis tarapacana, which will be subsequently used to reconstruct annual precipitation variations in southern Altiplano back to 1290 A.D. Precipitation estimates, based on regression analyses, were validated through statistical and graphical comparisons.