Climatic signals in tree-rings of Araucaria angustifolia in the southern Brazilian highlands



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.