Revealing Polylepis microphylla as novel Andean specie suitable for dendrochronology and quantitative wood anatomy

In the tropical Andes several species of the genus Polylepis have been reported to be useful to record climate variability using tree-ring width, expanding the geographical distribution of proxy records into the tropical region. However, in the tropics classical dendrochronology based on ring-width patterns is often challenging, hampering the development of climate reconstructions. Alternative methods can confirm annual periodicity of tree rings, and help on extracting more reliable climate information from them. To evaluate the dendrochronological potential of Polylepis microphylla, we propose the use of radiocarbon (14C) analyses as an independent method to validate the dendrochronological calendar dates couple with quantitative tree-ring anatomical features evaluations. P. microphylla is an endemic species from the Ecuadorian and the Peruvian Central Andes, which was described for the first time in 1861 but it has not yet been used in dendroclimatic studies.
Through dendrochronological and quantitative wood anatomy (QWA) methods, we generated several tree-ring chronologies covering the period 1965-2018 based on ring-width, cell wall thickness and lumen area from vessels and fibers. High-precision ¹⁴Cbomb pulse dating helped on confirming the annual periodicity in P. microphylla growth. Regarding the relationship with climate, significant correlations were found between ring-width and local temperature (i.e. positive during the current growing season) and precipitation (i.e. positive during prior and current growing season). QWA records exhibits similar results pointing out the potential of this approach to provide dendroclimatic records in the Central Andes.