Efectos de las condiciones meteorológicas extremas en los patrones de los ciclos diarios de los árboles de Polylepis reticulata

Abstract

Polylepis forests grow in the high Andes, forming the world's highest tree line while adapting to extreme climatic conditions. Despite their ecological significance, the daily patterns of stem cycles remain understudied. From 2018 to 2022, we monitored a Polylepis reticulata forest in the Ecuadorian Andes, utilizing high-resolution dendrometers to assess stem cycle responses to climatic events in large (LD) and small (SD) diameter classes. A peak threshold approach identified extreme events based on vapor pressure deficit (VPD). We employed multiple linear regression (MLR) to pinpoint key environmental factors influencing daily maximum stem shrinkage (MDS) and used random forest (RF) and regression tree (RT) techniques to determine growth drivers. During cold events, stem shrinkage was minimal, contributing 30% to annual growth, whereas warm events exhibited pronounced shrinkage, contributing less than 1%. The primary driver of MDS was maximum daily VPD, followed by precipitation. VPD is the main driver in radial growth, when VPD is <0.048 kPa higher growth rate was observed. The various responses to extreme conditions and the drivers of stem fluctuation provide key information on the possible impacts on these forests, affecting their development and adaptive capacity in the future.