Climatic signals in tree-rings of Araucaria angustifolia in the southern Brazilian highlands JULIANO MORALES OLIVEIRA, 1 * FIDEL ALEJANDRO ROIG 2 AND VALÉRIO DEPATTA PILLAR 1 1 Laboratório de Dendroecologia, Departamento de Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, 91540-000, Brazil (Email, juliano.oliveira@ufrgs.br); and 2 Laboratorio de Dendrocronología, Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales, Centro Científico Tecnológico CONICET-Mendoza, Mendoza,Argentina Abstract Araucaria angustifolia (Bertol.) O. Kuntze (Araucariaceae) is a Neotropical tree, widely distributed in subtropical mountain rain forests and nearby natural grasslands of Southern Brazil. This species produces annual growth rings, but its dendroclimatic potential is barely known. In the present paper, the long-term growth patterns of A. angustifolia were investigated using annual growth ring time series and association to climate over the last century.Wood cores of A. angustifolia trees growing in forest and grassland habitats were obtained with an increment borer.The cores were surfaced, measured and cross-dated.The dated ring-width time series were standardized and submitted to correlation and principal component analysis to verify growth trends among sites and trees. Growth- climate relationships were investigated using correlation and regression analyses, comparing the ordination axes scores to regional time series of precipitation and temperature. Due to anatomical irregularities, mainly partial rings, only 35 out of 60 trees were cross-dated. The correlation and ordination analyses showed common tree-growth trends within and between sites, indicative of a regional environmental force determining inter-annual cambial activity variation. Despite growing in distinct habitats and disturbance regimes, A. angustifolia trees share a common long-term growth pattern, which is significantly related to thermal conditions during the current and previous growing seasons. Moreover, site-specific characteristics may have influenced opposite growth responses and association to climate conditions between forest and grassland trees. Key words: Araucaria forest, Campos grassland, dendrochronology, fire, partial rings. INTRODUCTION Growth rings of woody plants are a major source of high-resolution data for studies of long-term environ- mental changes, especially in regions under strong sea- sonal climatic variability (Fritts 1976; Schweingruber 1996; Vaganov et al. 2006). Dendrochronological studies are scarce in tropical and subtropical ecosys- tems, despite promising results that have been obtained since the early 20 th century (see historical review in Mariaux 1981; Worbes 2002). The limited development of this science in the tropics can be attributed to the scarce frequency of tree species forming well-defined growth rings compared with temperate and arid floras (Stahle 1999). This situation has motivated an increasing number of studies dealing with the growth ring formation, particularly their wood anatomical features, the timing and dynamics of the tree ring formation and its links with phenological changes and climate seasonality (e.g. Boninsegna et al. 1989; Détienne 1989; Borchert 1999; Alves & Angyalossy-Alfonso 2000; Roig 2000; Callado et al. 2001; Roig et al. 2005; Lisi et al. 2008) The tropics represent a key piece in the understand- ing of the planetary climatic system. Since few long- term instrumental or proxy climatic data exist for this zone, most of the dendrochronological studies in subtropical and tropical regions have focused on the identification of climate-sensitive species and further development of growth ring chronologies that could be used as proxy data for climatological investigation (e.g. Villalba et al. 1998; Bhattacharyya & Yadav 1999; Buckley et al. 2000; Fowler et al. 2000; Biondi 2001; Morales et al. 2004; Speer et al. 2004; Brienen & Zuidema 2005; Dünisch 2005). Few studies developed tree ring chronologies for other ecological applications (e.g. Stahle et al. 1999; Grau et al. 2003; Worbes et al. 2003; Brienen & Zuidema 2006; Martin & Fahey 2006). Araucaria angustifolia (Bertol.) O. Kuntze (Araucari- aceae) is a southeastern South America conifer that produces seasonal growth rings, but its dendrochrono- logical potential is barely known. According to Oliveira *Corresponding author. Accepted for publication March 2009. Austral Ecology (2010) 35, 134–147 © 2009 The Authors doi:10.1111/j.1442-9993.2009.02018.x Journal compilation © 2009 Ecological Society of Australia