The Effects of Environmental Change on Polylepis pauta in the Ecuadorian Páramo

Abstract

Tropical tree ring analysis has been a rarity in the field of dendrochronology until recent years. Trees growing along the equator experience minimal limiting growth periods due to a lack of temperature seasonality, and therefore do not produce consistent visible rings. In regions where such aseasonality produces no dormancy period, it has been found that dry seasons mimic the limiting growth periods seen elsewhere in the cold winter. Stable isotope analysis has been proven effective for identifying these yearly dry and wet periods in tropical trees. This study aims to determine if stable isotope analysis is effective for the evaluation of annual growth patterns in the northern Andes. It also aims to determine whether environmental changes, including pollution, are affecting the growth of Polylepis pauta in central Ecuador. In total, 68 cores were collected at four distinct Polylepis pauta stands. A comparative approach between isotope levels in whole wood versus cellulose is being conducted and used to determine if differences in isotope content between the two methods exist. The remaining cores were subsampled and analyzed for δ15N and δ13C content. Assuming the results proceed as predicted, there will be peaks in δ13C corresponding to the dry months and vice versa; higher δ15N values are expected to represent pollution-derived nitrogen sources. These seasonal differences will allow the reconstruction of a paleoclimate timeline and pollution history throughout the life of the tree.