Dendroclimatology of high-elevation Nothofagus pumilio forests at their northern distribution limit in the central Andes of Chile

Nothofagus pumilio (Poepp et Endl.) Krasser, is a deciduous tree species that grows in Chile and adjacent Argentina between 36 and 56 degrees S, often forming the Andean tree line. This paper presents the first eight tree-ring chronologies from N. pumilio at its northern range limit in the central Andes of Chile (36-39 degrees S) and the first precipitation reconstruction for this region. Samples were taken from upper tree-line stands (1500-1700 m elevation) in three study areas: Vilches, Laguna del Laja, and Conguillio. Results indicate that, at the northern sites (Vilches and Laguna del Laja), the tree-ring growth of N. pumilio is positively correlated with late-spring and early summer precipitation and that higher temperatures reduce radial growth, probably because of an increase in evapotranspiration and decrease in water availability. At the southern Conguillio study area, radial growth was negatively correlated with late-spring and early summer precipitation. The presence of volcanic activity in this latter study area, which might have masked the climate signal, did not seem to have a significant influence on radial growth. A reconstruction of November-December (summer) precipitation for the period 1837-1996 from N. pumilio tree-ring chronologies accounted for 37% of instrumentally recorded precipitation variance. This is the first precipitation reconstruction from N. pumilio chronologies. Only temperature and snow cover have previously been reconstructed using this species. The reconstruction indicates that the driest and wettest 25-year periods within the past 160 years are 1890-1914 and 1917-1941, respectively.