Allometry and effects of extreme elevation on growth velocity of the Andean tree Polylepis tarapacana Philippi (Rosaceae)

Abstract

Increasing elevation can restrict the expansion of tree species by negatively affecting growth. In this study, we estimated growth velocity and evaluated the effects of extreme elevation on radial growth of the Andean tree Polylepis tarapacana Philippi (Rosaceae). We also developed different models to predict the relationship between age (number of tree-rings) and allometric characters (total height and diameter). Samples of trees and shrubs were collected between 4,200 and 4,600 m asl and analyzed using standard dendrochronological methods. Results evidenced that P. tarapacana is a slow-growing species since it grows less than 5 mm per year. Furthermore, elevation has a negative effect on radial growth. Morphometric models showed that a positive relationship between total height and diameter exists but not a significant relation between number of tree-rings and morphometry. Elevation had a major role in the radial growth of P. tarapacana which interacts with microclimatic conditions. Careful considerations should be made at the moment of using allometry as a surrogate for age in ecological studies.