2.1 Study site.
The study was carried out at the Ralco National Preserve (37°52’50.47” S
- 51°20’50, 90” O), specifically in the Quillaicahue River Valley with
an average altitude of 1,350 m above sea level. The climate has a
distinct snow season with a medium winter temperature below 0°C (Donoso
et al., 2014), with precipitations that can hold up to 4,000 mm in the
form of snow during winter (Veblen, 1982). The Ralco national reserve is
located in a zone with the strong influence of two large volcanoes, the
Callaqui (37˚56’S, 71˚ 26’W, 3100 m.a.s.l.) and the Copahue (37˚51’S
71˚10’W, 2979 m.a.s.l.). The geomorphological processes that formed this
high-altitude valley consist of series of volcanic, glacial, and fluvial
processes (Zaio & Mardones, 1991). Soils have developed on interlayered
pyroclastic materials and volcanic-derived fluvial deposits overlying an
old basaltic-andesitic lava flow. Like most national protected areas in
Chile, no comprehensive soil survey has been conducted (CONAF 1996).
Therefore, before establishing the sampling plots, we carried out a
general soil survey within May 2015 and May 2016, defining the prevalent
soils of the Quillaicahue valley, which were classified as eitherVitric hapludands and Vitrandic udortents (Soil Survey
Staff, 2014).
The site presents a temperate Andean resinous forest of Araucaria and
Dombeyi’s beech vegetation zone (Luebert & Pliscoff, 2006). The main
tree species is Araucaria araucana, accompanied byNothofagus dombeyi, Nothofagus obliqua, andNothofagus antarctica . The understory comprises evergreen shrubs
such as Colletia spinosa, Berberis sp, and sparse grasses such asFestuca sp., which is the primary palatable grazing
resource. Before creating this protected area, the historical
land use was associated with the productive activities present in this
region, mainly forestry and livestock grazing (Moreira-Muñoz & Borsdorf
2014). The Ralco national reserve was established in 1987 to protect the
most septentrional population of Araucaria araucana woods
alongside to its natural resources such as soil and water and allowing
the rational use of these resources by the indigenous communities (CONAF
1996). Despite the conservation efforts, there has been considerable
overgrazing in the communal fields during the snow-free seasons. Thus,
18 years ago, a fence was installed to separate the high grazing areas
from the low grazing areas. The differences between the high and low
grazing areas is mainly due to fencing and the proximity to the communal
grazing fields located directly north of our study areas.