Spatial variations of precipitation in the Bolivian Altiplano inferred from the world’s highest-elevation tree-ring records

MARIANO MORALES; RICARDO VILLALBA; CLAUDIA SOLIZ; JAIME ARGOLLO; DUNCAN A. CHRISTIE; JEANETTE PACAJES; JORGE MOYA

Vancouver, British Columbia, Canada

Conferencia; First American Dendrochronology Conference; 2008

Abstract: We document the dendroclimatological potential of Polylepis tarapacana to estimate past changes in temporal and spatial variations in precipitation across the Bolivian Altiplano (17-23°S). The P. tarapacana chronologies, which presently range between 110 and 705 years in length, represent the highest tree-ring records worldwide. Interannual variations in fourteen tree-ring chronologies (4000- 4850m elevation) were compared using correlation and principal component analyses. There is common signal among the studied chronologies. For the common interval 1890-1999, three dominant patterns of tree growth across the Bolivian Altiplano were identified. The first pattern, which explains 52% of the total variance in tree growth, is associated with years of above or below tree growth across the whole region. The second and third patterns, related to significant lower common variance (13 and 8% respectively), are associated with contrasting positive and negative rates of growth between the north and south sectors, and between the central-western sector and the remainder portions of the region, respectively. To determine the climatic significance of the spatial variations of P. tarapacana growth, the interannual patterns in tree growth were compared with spatial anomalies in precipitation across the region. Uniform patterns of above or below tree-growth are associated with previous-year positive or negative precipitation anomalies uniformly distributed across the whole Altiplano, respectively. Contrasting patterns of tree growth are related to opposite anomalies in precipitation during the previous year between sub-regions (north vs. south, central vs. north and south) in the Altiplano. Climatic preconditioning of tree-growth was also identified for some particular years. Our results indicate that the network of tree-ring chronologies of P. tarapacana in the Bolivian Altiplano has the potential to provide annually-resolved proxy precipitation reconstructions for the region over the past 5-7 centuries. This is an invaluable resource for documenting decade-to-century precipitation variability in the Altiplano and its links to large scale ocean-atmosphere circulation features.