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.