Polylepis wood acclimation strategies to ENSO events.

During the El Niño Southern Oscillation (ENSO), heat wave variations off the High Andean Puna (HAP) cause extreme droughts at high altitudes. A better understanding of the drought susceptibility of HAP Polylepis xeric-species is needed given the increasing frequency of desiccation and tree mortality. We evaluated the tree ring growth and vessel trait plasticity to ENSO intensities (neutral, weak, moderate, and strong) of two Polylepis xeric-species (Polylepis rugulosa and Polylepis tarapacana). We demonstrated annual ring width and vessel trait differences between La Niña and El Niño events for both species. We showed that specific vessel traits exhibit coordination with water-use efficiency in response to ENSO events, thereby reducing vulnerability to hydraulic failure. When assessing the effects of ENSO events on specific vessel traits, special attention should be paid to traits that confer resilience, resistance, and recovery to growth of these species. This knowledge is essential to suggest that this adjustment to ENSO events may increase their capacity to tolerate and adapt to new extreme climatic conditions in the HAPs.