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.