Temporal Growth Variation in High-Elevation Forests: Case Study of Polylepis Forests in Central Andes

Polylepis species form the dominant high-altitude forests in the tropical Andes, one of the most vulnerable regions to future climate change scenarios. The study of the growth of these forests provides useful information about their ontogeny and the environmental conditions where they develop. The identification of growth patterns is relevant for understanding the dynamics of the forests in response to climatic variables. In this chapter, we present a brief review of dendroecological studies on Polylepis species. We also developed for the first time in the central Andes of Peru three new Polylepis ring-width chronologies together with a diameter growth modeling for the following species: Polylepis rodolfo-vasquezii, Polylepis rugulosa, and Polylepis tarapacana. Dendrochronological techniques together with a biologically based model help us to obtain information on forestry traits of Polylepis species. P. rodolfo-vasquezii to growth response to summer temperature of the current growth period determined radial growth, whereas spring and summer precipitation from the previous growth period determined the radial growth in P. rugulosa and P. tarapacana, respectively. The radial growth models indicated differences in the growth of the three Polylepis species with P. rodolfo-vasquezii reaching the highest rate (0.11 cm/yr), while P. tarapacana showed the lowest (0.08 cm/yr). Due to the low growth rates of these Polylepis species, long periods (>100 years) are required to establish and provide ecosystem services. As these forests face the challenge of climate change and anthropogenic pressure, there is a clear need to obtain precise information in order to formulate guidelines for the conservation of these forests, and the application of dendroecology is indispensable in this context.