Growth patterns of secondary Nothofagus obliqua?N. alpina forests in southern Chile

Abstract

The environmental factors that influence the diameter-growth of the Nothofagus obliqua and Nothofagus alpina were investigated in secondary forests in southern Chile. A total of 17 edaphic, topographic and climatic variables were studied. The annual periodic diameter increment (API) in 15 and 20 year-old trees was measured using dendrochronological techniques. A multiple correspondence factorial analysis (MCFA) indicated that longitude, minimum precipitation, summer humidity index, frost-free period, maximum drought period, and percentage of silt and sand in the soil were driving variables influencing diameter-growth. The first three factors accounted for 70% of the total variation. Higher diameter-growth rates were associated with intermediate annual rainfall, a short dry period, and sandy soil. Lower rates were associated with an intermediate frost-free period, a low summer humidity index, a long dry period and silty soil. A spatial pattern of the driving variables was found in the study area. The first two factors showed a longitudinal division separating the sites located in the Central Depression, Coastal Range and Andean Range. Using the results generated by MCFA, an ascendant hierarchic classification analysis (AHCA) was conducted to classify the study area into five sites of homogeneous productivity. The highest diameter-growth (>7.1 mm per year) sites were located in the pre-Andes of Valdivia Province, followed by sites in the northern pre-Andes of Cautin Province and the Andean Range of both provinces. Intermediate growth rates corresponded to the coastal site. The lowest diameter-growth (<5.3 mm per year) was located in the Central Depression in both provinces. The use of multivariate methods and the adequate selection of environmental variables enabled us to identify the diameter-growth driving variables, as well as to classify the study area into five productivity categories.