Climate sensitivity in radial growth of the northernmost population of Polylepis tarapacana in the Peruvian Andes

DORIS B. CRISPÍN-DELACRUZ; EDILSON J. REQUENA-ROJAS; MARIANO S. MORALES; JANET G. INGA GUILLEN; DUNCAN A. CHRISTIE; LAIA ANDREU HAYLES

San Francisco

Conferencia; AGU fall meeting; 2019

Polylepis tarapacana is a highly resistant tree species that is well adapted to extreme conditions. This tree specie is growing in very high altitude environments between 4000 and 5000 m a.s.l. and its distribution ranges from 16º S to 23ºS along the South American Altiplano. Tree-ring width chronologies of P. tarapacana have been widely used for drought and precipitation reconstructions for South America. Here, we present a 400-year tree-ring width chronology developed from the northernmost population of P. tarapacana located at 17º S and 69º W in southern Peru. This is the P. tarapacana tree-ring record closest to the equator. In order to study the influence of climate variability on P. tarapacana growth, precipitation and temperature instrumental data were used for correlation analyses. Our results show that this ring-width chronology is highly sensitive to the prior summer season (Dec-Feb) precipitation variability when the South American monsoon (SASM) reaches its maximum intensity. In addition, we also found negative correlation with temperatures for those months of the previous growing season. In the Altiplano, higher temperatures increase evapotranspiration and reduce water availability and thus, they may constrain radial growth,. Finally, strong relationships were found between the El Niño Southern Oscillation (ENSO) and tree growth variability with positive correlations during the current growing season and negative during the previous growth period. This result is consistent with the well-known ENSO influence on climate conditions over the Altiplano, that is negative (positive) related to precipitation (temperature). Therefore, in this site the growth of P. tarapacana is strongly influenced by the amount of moisture availability that is linked to large-scale climate patterns such as the SASM and ENSO.