Differential growth rates through the seedling and sapling stages of two Nothofagus species underplanted at low-light environments in an Andean high-graded forest

Abstract

The Andes of south-central Chile, with the valuable and dominant timber species Nothofagus dombeyi and N. alpina, have been heavily high-graded. Restoring these forests with these species is challenging since they are light demanding and the understory becomes dominated by bamboo (Chusquea culeou), which prevents natural regeneration. In this study we aimed to evaluate the root-collar diameter (RCD) and height growth response of these species during their seedling and sapling stages (years 1, 2, 3 and 6) after outplanting and removing the understory in a relatively low-light environment in a high-graded forest (incident light levels between 2.6 and 12.7 mol m−2 d−1). We fitted regression models to predict annual growth as a function of light availability, and used species as an indicator variable. RCD growth was significantly affected by light since the onset, and height growth only at ages 3 and 6. Species became a significant variable only at years 3 and 6 for RCD growth, and at age 6 for height growth. N. dombeyi grew faster than N. alpina throughout all the period, and both species had their greatest response to light the last years evaluated (adj. r 2 of 0.67 and 0.45 in RCD and height growth, respectively), i.e. an increasing intolerance to shade (ontogenetic change). The increasing variability of the data and the goodness-of-fit of the models at this stage suggest that light is becoming a major driver of growth. These results illustrate a good potential use of these species for restoration of Andean forests.