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

Abstract

Polylepis species form the dominant high-altitude forests in the tropicalAndes, one of the most vulnerable regions to future climate change scenarios. Thestudy of the growth of these forests provides useful information about their ontogenyand the environmental conditions where they develop. The identification ofgrowth patterns is relevant for understanding the dynamics of the forests in responseto climatic variables. In this chapter, we present a brief review of dendroecologicalstudies on Polylepis species. We also developed for the first time in the centralAndes of Peru three new Polylepis ring-width chronologies together with a diametergrowth modeling for the following species: Polylepis rodolfo-vasquezii, Polylepisrugulosa, and Polylepis tarapacana. Dendrochronological techniques together with a biologically based model help us to obtain information on forestry traits ofPolylepis species. P. rodolfo-vasquezii to growth response to summer temperature ofthe current growth period determined radial growth, whereas spring and summerprecipitation from the previous growth period determined the radial growth in P.rugulosa and P. tarapacana, respectively. The radial growth models indicated differencesin the growth of the three Polylepis species with P. rodolfo-vasquezii reachingthe 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 thechallenge of climate change and anthropogenic pressure, there is a clear need toobtain precise information in order to formulate guidelines for the conservation ofthese forests, and the application of dendroecology is indispensable in this context.